Class 10 - Science - Ch1 - Chemical Reactions & Equations
Ch1 - Chemical Reactions & EquationsMCQs, Q & A, NCERT
Solutions
Q1: A chemical reaction involves ina. Only breaking of bondsb.
Only formation of bondsc. Both breaking and formation of bondsd.
None of these
Answer: (c) Both breaking and formation of bonds
Q2: A balanced chemical equation always obeysa. Law of
conservation of massb. Law of thermal equilibriumc. Law of
conservation of energyd. All of the above
Answer: (a) law of conservation of mass.
Q3: Single displacement reaction involves:a. Oxidationb.
Reductionc. Redoxd. Heating
Answer: (c) redox
Q4: String of ants, bees containa. Formic acidb. Vinegarc.
Succinic acidd. Common Salt (NaCl)
Answer: (a) Formic acid
Q5: Some stale food gives a bad taste and a bad smell because
of:a. Corrosionb. Displacementc. Heatingd. Rancidity
Answer: (d) rancidity
Q6: A red brown gas is released on heating lead nitrate. It is
an example ofa. Combination reactionb. Oxidation reactionc.
Decomposition reactiond. Reduction reaction
Answer: (c) Decomposition
Q7: The sign indicatesa. release of gasb. dissolution of gasc.
formation of a precipitated. lowering of temperature
Answer: (c) formation of a precipitate
Q8: Why do gold and silver do not corrode?Answer:It is because
they are less reactive.
Q9: What do you mean by balanced chemical equation?
Answer: An equation that has equal number of atoms of each
element on both the sides of equation is called balanced chemical
equation, i.e., mass of the reactants is equal to mass of the
products. e.g., 2Mg + O2 2MgO
Q10: Define rancidity.Answer: When fats and oils are oxidized,
they become rancid and their smell and tastechange. This process is
known as rancidity.
Q11 (CBSE 2007): Write the type of reactions in the following:
i. Reaction between an acid and a baseii. Rusting of iron
Answer: i. Neutralization reaction ii. Oxidation reaction
Q12: Give an example of decomposition reaction where energy is
supplied in form of light.Answer: sunlight 2AgBr(s)
------------------------> 2Ag (s) + Br2(g) (Silver Bromide)
Q13: Why does copper vessel acquire green coating in rainy
season?Answer: It reacts with CO2 in the atmosphere and forms a
layer of basic Copper Carbonate.
Q14: What is the name of the gas which burns with a pop
sound?Answer: Hydrogen gas.
Q15: Why is Hydrogen peroxide stored in coloured bottles?Answer:
It is done to prevent photolytic decomposition of hydrogen
peroxide.
Q16: Name the oxidizing agent and reducing agent in the
following equation. 3MnO2(s) + 4Al(s) 3Mn(s) + 2Al2O3(s)ORName a
reducing agent that may be used to obtain manganese from manganese
dioxide.
Answer: Reducing agent : Al Oxidation Agent : MnO2Q17: Give two
example from everyday life situations where redox reactions are
taking place.
Answer: Corrosion and Rancidity
Q18: In electrolysis of water, why is the volume of gas
collected over one electrode double that of gas collected over the
other electrode ?
Answer: In water (H2O), hydrogen and oxygen are present in the
raito of 2:1 by volume.
Q19: Why should a magnesium ribbon be cleaned before burning in
air?
Answer: Magnesium is a reactive metal. It combines with oxygen
of air to form a layer of magnesium oxide on its surface. Hence, it
should be cleaned with a sand paper before burning to remove the
oxide layer formed on its surface.
Q20: Explain how respiration is an exothermic reaction.
Answer: During digestion, food is broken down into simpler
substances. For example, rice, potatoes and bread contain
carbohydrates. These carbohydrates are broken down to form glucose.
This glucose combines with oxygen in the cells of our body and
provides energy. Hence, respiration is an exothermic process.
C6H12O6(aq) + 6O2(aq) 6CO2(aq) + 6H2O(l) + energy (Glucouse)
Q21: What factors influence the rate of chemical reaction?
Answer: Following are the factors that can influence the rate of
reaction: Nature of Reactants. e.g. Mg reacts faster in HCl than in
acetic acid. Concentration of reactants Surface Area of reactants.
E.g. Powdered CaCO3 reacts quickly than marble chips. Temperature
Catalyst
Q22: Define Endothermic reaction.
Answer: The reactions in which heat is absorbed are called
endothermic reactions. In such reactions heat is shown as one of
the reactants. If exact amount of heat absorbed is known then this
amount is written otherwise simply the word heat is written.E.g.
N2(g) + 2O2(g) + heat 2NO(g) nitric oxide
Q23: A silver ware is kept in a solution of CuSO4 (aq). What
change do you expect?Answer: No reaction. because Silver is less
reactive than copper.
Q24(CBSE exam): Name one metal when placed in ferrous sulphate
solution will discharge its green colour. Write a chemical equation
and state the reasons also.
Answer: Potassium(K) is one example. K is more reactive than
iron and will replace it. 2K + FeSO4 K2SO4 + Fe Potassium + Iron
Sulphate Potassium Sulphate + Iron
Q25: Why do we apply paint on iron articles?Answer: Iron
articles are painted to prevent them from rusting. Rusting is
oxidation of iron in the presence of air and moisture. The paint
layer cuts off the the contact of iron articles from moisture and
air.
Q26(CBSE): A solution of a substance ''X'' is used for white
washing(i) Name the substance ''X'' and write its formula(ii) Write
the reaction of the substance ''X'' named in (i) above with water.
Answer: (i) The substance ''X'' used for white washing is quick
lime (calcium oxide). Its formula is CaO.(ii) When quick lime is
mixed with water, the following reaction takes place:
CaO (s) + H2O(l) Ca(OH)2(aq) Quick Lime Water Slaked Lime
(Calcium Oxide) (Calcium Hydroxide)
The white suspension of slaked lime when applied on the walls,
combines with carbon dioxide (in air) forming a thin shining layer
of calcium carbonate.
Ca(OH)2(aq) + CO2(g) CaCO3(s) + H2O(l)Slaked Lime Calcium
Carbonate
Q27(CBSE): Why is it important to balance a chemical
equation?Answer: The balancing of chemical equation is done to
satisfy the law of conservation of mass, i.e. "total mass of all
the products of reaction in a chemical reaction is equal the total
mass of all the reactants".
Q28: What are the coefficients of the correctly balanced
equation? ? Fe2O3 + ? CO ? Fe + ? CO2(a) 0, 2, 2, 3(b) 1, 3, 2,
3(c) 1, 2, 2, 2(d) 2, 6, 4, 3
Answer: (b) Ferric Oxide + Carbon Mono-oxide Iron + Carbon
DiOxide
Q29: What are the coefficients of the correctly balanced
equation? ? BaCl2 + ? Al2(SO4)3 ? BaSO4 + ? AlCl3 (aq)(a) 1, 1, 1,
2(b) 3, 2, 3, 2(c) 3, 1, 3,2(d) 2, 1, 1, 2
Answer: (c) 3 BaCl2 + 1 Al2(SO4)3 3 BaSO4 + 2 AlCl3 (aq)
Barium Chloride + Aluminium Sulphate Barium Sulphate + Aluminium
Chloride
Q30(CBSE2011): What is the colour of FeSO4.7H2O crystals ? How
does this colour change upon heating ? Give balanced chemical
equation for the changes.
Answer: Hydrated ferrous sulphate crystals are green in colour.
On heating, single reactant breaks down to give simpler products.
This is a decomposition reaction.
Ferrous sulphate crystals (FeSO4.7H2O) lose water when heated
and the colour of the crystals changes. It then decomposes to
ferric oxide (Fe2O3), sulphur dioxide (SO2) and sulphur trioxide
(SO3). Ferric oxide is a solid, while SO2 and SO3 are gases.
You may use Wolfram Chemical Reaction Calculator E.g. Type lime
+ Water --> Calcium Hydroxide
Chemical Reaction Calculator Top of FormEnter chemical
equation:
Submit
Bottom of FormComputing...Get this widgetBuild your own
widgetBrowse widget galleryLearn moreReport a problemPowered by
Wolfram|AlphaTerms of use Share a link to this widget:More
Embed this widget
Q31: Quick like (CaO - Calcium Oxide) reaction with water is
regarded as exothermic. A student mixes these two products in a
test tube and touches its side surface. Which of the following
statement correctly describes the student's observation?
(a) The test tube becomes cold due to release of heat energy.(b)
The test tube becomes hot due to release of heat energy.(c) The
test tube becomes hot due to absorption of heat energy.(d) The test
tube becomes cold due to absorption of heat energy.
Answer: (b) The test tube becomes hot due to release of heat
energy.
Q32: The decomposition of vegetable matter into compost is an
example of _____.(Choose the correct option). (a) endothermic
reaction.(b) exothermic reaction.
Answer: (b) exothermic.
Q33(CBSE): Write a balanced chemical equation to represent the
following reaction: Iron reacts with steam to form Iron(II,III)
oxide and hydrogen gas.
Answer: 3Fe(s) + 4H2O(l) Fe3O4(s) + 4H2(g) Iron Water Iron Oxide
Hydrogen
Q34(CBSE): Identify the substance oxidized, substance reduced,
oxidising agent and reducing agent. MnO2 + 4HCl MnCl2 + 2H2O +
Cl2
Answer: Substance Oxidised: HCl Substance reduced: MnO2 Reducing
Agent: HCl Oxidising Agent: MnO2
Q35: Bromine gas (Br2) reacts with Sodium Carbonate (Na2CO3) in
aqueous solution and gives sodium bromide (NaBr), sodium bromate
(NaBrO3) and carbon-dioxide gas. How many number of sodium bromide
molecules obtained in the balanced chemical equation.
Answer: From the question, we infer the unbalanced chemical
equation is: Br2 + Na2CO3 NaBr + NaBrO3 + CO2
Balanced equation is: 3 Br2 + 3 Na2CO3 5 NaaBr + NaBrO3 + 3 CO2
It means 5 molecules of NaBr are obtained.
Q36: A numismatist (coin collector) has been collecting gold
coins, silver coins and copper coins for a long time. One day he
observed a black coating on silver coins and green coating on
copper coins. What chemical process is responsible for these
coatings. Also name the chemical formula of the black and green
coatings.
Answer: The coating occurred due to a chemical process called
corrosion. Black coating is due to deposit of Silver Sulphide
(Ag2S). Green coating is due to formation of Copper Carbonate
(CuCO3)(Note: Silver usually is corrosion resistant and does not
oxidize. However presence of sulphur gases in atmosphere can react
and cause sulphur-corrosion. )
Q37: Methane gas (CH4) when burns with oxygen (O2) gives carbon
dioxide and water. Write the balanced chemical equation and provide
the following information in terms of reactants and products in the
equation.(a) no. of molecules (b) no. of moles(c) molar mass(d)
total mass of reactants and productsWhat does statement (d)
infer?
Answer: The balanced chemical equation is: CH4 (g) + 2 O2(g)
2H2O (l) + CO2(g) Methane + Oxygen water + carbon di-oxide
ReactantsProducts
a. No. of moldeculesCH4 (g),O2(g) H2O, CO2(g)
b. no. of moles1 mole of CH4+ 1 mole of O2(g)2 moles of H2O + 1
mol of CO2
c. molar mass16g of CH4+ 64g of O2 44g of H2O + 36g of CO2
d.total mass80g 80g
CBSE Class 10 - Science - CH3 - Metals and Non-Metals Metals and
Non-Metals
Q & A
Q1: List any five physical properties of metals.
Answer: Physical properties of metals are:1. Metals are usually
hard (exceptions are: sodium and potassium). 2. These are sonorous.
3. These are lustrous. 4. Metals exhibit malleability and
ductility. 5. Mostly they are solids (exception is mercury) 6. They
exhibit high tensile strength. 7. These have high densities.
Q2: Are metals electronegative or electropositive?
Answer: Metals are electropositive i,e. they form cations by
loosing electrons.
Q3: Define Malleability.
Answer: Malleability is the property of a metal, by which it can
be beaten into thin sheets.
Q4: Name a metal which can be cut with a knife?
Answer: Sodium
Q5: Give examples of metals which are found in liquid form at
room temperature.
Answer: Mercury and Gallium
Q6: Define ductility. Give two examples of metals that exhibit
this property.Answer: Ductility is the property of a metal by which
it can be drawn into thin wires. e.g. gold and silver.
Q7: Give an example of metal which is i. the best conductor of
heat ii. the poor conductor of heat
Answer: (i) Silver (ii) lead
Q8: What are metalloids? Give examples of metalloids.
Answer: The elements that exhibit properties of both metals and
non metals are called metalloids.e.g. bismuth, silicon, germanium,
arsenic, antimony, tellurium and polonium
Q10: What are minerals?
Answer: The Inorganic elements or compounds of various metals
found in nature, associated with their earthly impurities are
called Minerals.
Q11: Can metals be extracted from all types of minerals?
Answer: No. Some minerals may have high percentage of metals
while other do not.
Q12: What are ores?
Answer: Those minerals from which metals can be extracted
profitably and conveniently are called Ores.
Q13: Define metallurgy.
Answer: The process of extracting metals from their ores
followed by refining is known as metallurgy.
Q14: Give an example of non-metal which is lustrous.
Answer: Iodine
Q15: Give an example of a non-metal which is hard and has high
melting point.
Answer: Diamond (allotrope of Carbon)
Q16: What is gangue and what is concentration?
Answer: Ores are usually associated with unwanted earthly matter
called gangue (sand, clay etc.,) and the removal of this unwanted
impurity is called concentration. The gangue has to be removed
before the extraction of metals.
Q17: Why do potato chips manufacturers fill the packet of chips
with nitrogen gas?
Answer: Nitrogen provides an inert atmosphere to prevent chips
from getting oxidised.Nitrogen is an antioxidant which prevents
oxidation of substances and that's why such type of food material
is flushed with nitrogen in packs.
Q18: Name any non-metal which is found in liquid state at room
temperature.
Answer: Bromine
Q19(KVS): You are given two statements a and b, select the
correct inference from this:
a. Metals conduct heat.b. Diamond is the best conductor of
heat.
i. Hence diamond is a metalii. Statement a is correctiii.
Statements a and b is correctiv. None of the above
Answer: ii. Statement a is correct
Q20: Write differences between metals and non-metals based on
physical properties.
Answer:SNo.Physical PropertyMetalsNon-Metals
1.Physical StateMetals are solid at room temperature. Exceptions
are mercury, cesium and gallium.Non-metals generally exist as
solids and gases, except Bromine which is a liquid
2.Melting and Boiling PointsMetals generally have high melting
point and high boiling point. (exceptions are Na and K)Non-metals
have low melting pt and low boiling point. (exceptions are C, Si
and B)
3.HardnessMetals are generally hard. (exceptions are Na and k
which can be cut by knife).Generally soft. (exceptions is diamond,
the hardest substance)
4.LustreBright metallic lustre. Usually silvery white appearance
except gold (yellow) and Cu (pinkish red)Lack Lustre (exceptions
are iodine and graphite which are lustrous)
5.DensityHave high density (exceptions: Na, K and Ca. Na and K
float on water)Generally low density except diamond which has high
density.
6.MalleabilityMalleable Non-malleable
7.DuctilityDuctileNon-ductile
8.TenacityUsually have high tensile strength. (exceptions are
Na, K and Hg which are non-malleable, non-ductile and have low
tenacity).Lack tenacity.
9.BrittlenessUsually hard but not brittle. (exception is Zn
which is brittle at room temperature.)Generally brittle.
10.ConductanceIn general metals are good conductors of heat and
electricity. (exception is Bi)Usually non-conductors. (exceptions
are graphite and gas carbon)
11.SolubilityUsually do not dissolve in liquids except by
chemical reaction.Dissolve in liquid solvents.
12.Alloy and AmalgamUsually make alloys and amalgams.Do not form
alloys except carbon which alloys with iron to form steel.
(In progress...)Class 10 - Science - CH4 - Carbon and Its
Compounds (Q & A) Class 10 - Carbon and Its Compounds
cellulose(credits:wpclipart)
Q1. What is next homologue of C3H7OH is called?Answer: The next
homologue of C3H7OH is called butanol C4H9OH.
Q2. What is the molecular formula of the alcohol which can be
derived from propane?
Answer: Propane: CH3-CH2-CH3 or C3H8Alcohol obtained from
propane is C3H7OH.
Q3. What is meant by the term functional group?
Answer: An atom or a group of atoms, which makes a carbon
compound reactive and decides itsproperties. is called a functional
group.
Q4. Give the names of the functional groups: (CBSE 2007) i) -CHO
(ii -C=O
Answer: (i) Aldehydic group (ii) Ketonic group.
Q5. Give the names of the following functional groups: (CBSE
2007) i) OH (ii) COOH
Answer: (i) Alcoholic (ii) Carhoxylic.
Q6. Which functional groups always occur at the terminal
position of a carbon chain?
Answer: Aldehydic group RCHO (R is tue alkyl group), and
Carboxyl group RCOOH (R is the alkyl group).
Q7. Why a candle flame burns yellow, while a highly-oxygenated
gas-fuel flame burns blue?
Answer: The most important factor determining color of the flame
is oxygen supply and the extent of fuel-oxygen pre-mixing, which
determines the rate of combustion and thus the temperature and
reaction paths, thereby producing different color hues. In case of
candle, it is an incomplete combustion and the flame temperature is
not high. This gives a yellow flame. While a highly-oxygenated gas
(e.g. ethyne) flame burns blue because of complete combustion
raising a very high temperature.
Q8. Why is the reaction between methane and chlorine considered
a substitution reaction? [CBSE 2008]
Answer: Methane reacts with chlorine in the presence of sunlight
to form chloromethane and hydrogen chloride. CH4+ Cl2 CH3Cl +
HClWith the excess of chlorine, aH the four hydrogen atoms of
methane are replaced by chlorine atoms to form carbon tetrachloride
(CCl4). This reaction is considered as substitution reactions
because hydrogen of methane is substituted by chlorine.
Q9: Why does Carbon form compounds mainly by covalent
bonding?
Answer. Being tetravalent carbon atom, it is neither capable of
losing all of its four valance electrons nor it can easily accept
four electrons to complete its octet. Both of these are
requirements of ionic bond formation and are energetically less
favourable. Carbon completes its octet by sharing of electrons and
hence covalent bonding is preferred.
Q10. Give a chemical test to distinguish between saturated and
unsaturated hydrocarbons.
Answer. When saturated compounds are burnt in air, they give a
clear (blue) flame but the burning of unsaturated compounds (akenes
and alkynes) gives a sooty (yellowish) flame. Actually, saturated
compounds contain comparatively less percentage of carbon which get
completely oxidized by the oxygen present in air. On the other
hand, the percentage of carbon in unsaturated compounds is more and
it requires more oxygen to get completely oxidized that is not
fulfilled by air. So due to incomplete oxidation they burn with a
sooty flame.
Bromine-water test: Br2water is a brown coloured liquid.(a)
Unsaturated hydrocarbons give addition reaction with Br2. So the
colour of Br2-water gets decolourized. R-C=C-R + Br2 R-BrC-CBr-R(b)
Saturated hydrocarbons do not react with Br2-water, so the colour
of Br2.-water does not get decolourised.
Q11: What do you mean by Octane Rating?
Answer: Gasolines are rated on a scale known as octane rating,
which is based on the way they burn in an engine. The higher the
octane rating, the greater the percentage of complex-structured
hydrocarbons that are present in the mixture, the more uniformly
the gasoline burns, and the less knocking there is in the
automobile engine. Thus, a gasoline rated 92 octane will burn more
smoothly than one rated 87 octane.
Q12: Two compounds A and B react with each other in the presence
of a dehydrating agent to produce an ester. Both react with Na to
evolve hydrogen gas. On reaction with Na2CO3 only A evolves CO2.
Identify the functional groups present in A and B giving reason for
your answer.
Answer: Compound A contains COOH group while compound B contains
OH group.
Since carboxylic acids and alcohols react with each other to
form an ester, out of A and B, one is an alcohol and the other is a
carboxylic acid. This is further strengthened by reaction of both
with Na to evolve hydrogen gas.Only carboxylic acids react with
Na2CO3 to evolve CO2, A contains COOH group while B contains OH
group.
Following video posted on You tube by tutor vista nicely
summarizes this chapter:
Q13:An organic compound 'X' is widely used as a preservative in
pickles and has a molecular formula C2H2O2. This compound reacts
with ethanol to form a sweetsmelling compound Y'. a. Identify the
compound X b. Write the chemical equation for its reaction with
ethanol to form compound Y. c. How can we get compound X back from
Y? d. Name the process and write corresponding chemical equation.
e. Which gas is produced when compound X reacts with washing soda?
Write the chemical equation.
Answer:a. Compound X is ethanoic acid which gives and ester (Y)
when reacts with ethanol.b. CH3COOH + CH3CH2OH CH3COOC2H5c. Esters
gives back alcohol and carboxylic acid in the presence of acid or
base.d. CH3COOC2H5 ---NaOH C2H5OH + CH3COOHe.CO2 gas is released.
CH3COOH + Na2CO3 2CH3COONa + H2O + CO2
Q14(NCERT): What would be the electron dot structure of carbon
dioxide which has the formula CO2?
Answer: Electron dot structure of CO2 is O=C=O
Q15(NCERT): What would be the electron dot structure of a
molecule of sulphur which is made up of eight atoms of sulphur?
(Hint The eight atoms of sulphur are joined together in the form of
a ring.)
Answer: S8 electron dot structure are in two forms:
Q16(NCERT): How many structural isomers can you draw for
pentane?
Answer: There are three structural isomers of pentane:(i)
Pentane CH3 CH2 CH2 CH2 CH3
(ii) 2-methyl Butane (iso-pentane) CH3CH2CHCH3 | CH3(iii) 2-2
dimethyl propane (neo-pentane) CH3 | CH3 CH CH3 | CH3
Q17(NCERT): What are the two properties of carbon which lead to
the huge number of carbon compounds we see around us?
Answer: Two properties of carbon that attributes to its large
family of carbon compounds are:1. Catenation: Ability to form
chains with other atoms of carbon by covalent bonding. 2.
Tetravalency: Valency = 4 i.e. it forms four covalent bonds with
four other atoms.
Q18: What is Covalent bonding?
Answer: The chemical bonding occurs due to mutual sharing of
electron pairs of two or more atoms of different elements is called
covalent bonding. By mutual sharing of electron pairs atom attain
noble gas configuration. e.g. In Hydrogen molecule (H2), the two
H-atoms combine by covalent bonding (H-H).
Q19: What are Hydrocarbons? Give examples.
Answer: Compounds of carbon and hydrogen are called
hydrocarbons. Methane, Ethane, Butane, ethyne, propene, benzene,
petroleum products all are examples of hydrocarbons.
Q20(CBSE 2011): What are saturated hydrocarbons?
Answer:The hydrocarbons in which valency of carbon is satisfied
by a single covalent bond are called saturated hydrocarbons.
Alkanes like methane (CH4), ethane(C2H6), propane(C3H8) etc. are
examples of saturated hydrocarbons. Saturated hydrocarbons will
generally give a clean flame.
Q21(CBSE 2011): "Saturated hydrocarbons burn with a blue flame
while unsaturated hydrocarbons burn with a sooty flame". Why?
Answer: Saturated hydrocarbons have only C-C and C-H single
bonds and thus contain the maximumpossible number of hydrogen atoms
per carbon atom. With sufficient oxygen, saturated hydrocarbons
burn completely and give blue flame.CH4 + 2O2 CO2 + 2H2OUnsaturated
hydrocarbons contain a carbon-carbon double bond (C=C) or triple
bond (CC). Hence they contain less number of hydrogen than carbon.
Unsaturated hydrocarbons undergoe incomplete combustion and give
yellow flame along with black sooty(carbon). C2H4 + O2 CO2 + 2H2O +
C(s)
Q22: What are isomers?
Answer: Compounds with identical molecular formula but different
structures are called structural isomers. Organic compounds show a
great level of isomerism. Isomers may be structural (due to
difference in arrangement of C atoms forming chain) or stereo (due
to arrangement of bonds in chain). With increase in number of
carbon atoms in a molecular formula leads to increase in number of
isomers. CCCC OR C-C-C | C
Q23(NCERT):Why do ionic compounds have high melting points?
Answer: Ions have strong electrostatic forces of attraction
among them forming ionic compounds. It requires lot of energy to
break these ionic bonds or forces. That's why ionic bonds have high
melting points.
Q24: What are the characteristics of Homologue series?
Answer: Important characteristics of Homologue series are:1.
Have same general formula. 2. Belong to same functional group. 3.
Have general methods of separation. 4. Have similar chemical
properties. 5. Show similar gradation of physical properties. e.g.
boiling points of alcohol increase with increase in their molecular
weights. 6. Similarly solubility decreases with increase in
molecular weights.
Q25: What is the general formula of Alkanes?
Answer: CnH2n+2
Q26: What is a hetroatom? What is the hetroatom in alcohol
functional group?
Answer: In a hydrocarbon chain, one or more hydrogen atoms can
be replaced by other atoms according to their valencies. The
element which replaces hydrogen in the chain is called a
heteroatom.e.g. in alcohol (-OH) functional group, oxygen is the
hetroatom.
. CBSE Class 10 - Science - CH2 - Acids, Bases and Salts
credits:clker.com
MCQs, NCERT Solutions, Q & A
Q1: The most commonly used indicator in laboratory is(a) Methyl
Orange(b) Litmus(c) Phenolphtalein(d) Universal Indicator
Answer: Universal Indicator
Q2: Olfactory indicators are:(a) Clove(b) Turmeric(c) Soap(d)
Rose Petals
Answer: (a) Clove
Q3: An element common to all acids is(a) Chlorine(b) Nitrogen(c)
Oxygen(d) Hydrogen
Answer: (d) Hydrogen
Q4: Metal carbonate on reaction with dilute acid release(a)
CO2(b) CO(c) H2O(d) H2
Answer: (a) CO2
Q5 (Teachers FA manual): ln general, salts(a) are ionic
compounds(b) contain hydrogen ions(c) contain hydroxide ions(d)
turn litmus red
Answer: (a) are ionic compounds
Q6: On passing excess of CO2 gas in an aqueous solution of
calcium carbonate, milkiness of the solution(a) persists(b)
fades(c) deepens(d) disappears
Answer: (b) fades
Q7(FA manual): When magnesium and hydrochloric acid react, they
produce(a) Oxygen and magnesium chloride(b) Chlorine and magnesium
oxide(c) Hydrogen and magnesium chloride(d) Hydrogen and magnesium
oxide
Answer: (c) Hydrogen and magnesium chloride
Q8: Dissolution of acid or base in water is(a) Exothermic(b)
Endothermic(c) Violent(d) None of these
Answer: (a) ExothermicQ9: Water contains more H+ ions than OH-
ions. In this case, water is(a) neutral(b) basic(c) acidic(d)
cannot say.
Answer: (c) acidic
Q10: When an acid reacts with a base what compounds are
formed?(a) water only (b) metal oxides only(c) a salt only (d) a
salt and water
Answer: (d) a salt and water
Q11: Which of the following is a property of an acid?(a)
slippery feel(b) non-reactive(c) sour taste(d) strong color
Answer: (c) sour taste
Q12: On diluting an acid concentration of H+ per unit volume(a)
increases(b) decreases(c) remains unaffected(d) depends on type of
acid used.
Answer: (b) decreases
Q13: What is pH?(a) the positive logarithm of the hydroxide ion
concentration(b) the positive logarithm of the hydrogen ion
concentration(c) the negative logarithm of the hydroxide ion
concentration(d) the negative logarithm of the hydrogen ion
concentration
Answer: (d) the negative logarithm of the hydrogen ion
concentration
Q14: Tartaric acid is the constituent of(a) bleaching powder(b)
baking powder(c) washing powder(d) plaster of paris
Answer: (b) baking powder
Q15: A solution turns blue litmus red. Its pH value is likely to
be(a) 4(b) 7(c) 9(d) 12
Answer: (a) 4
Q16: What is the name of H2SO3?(a) Sulphuric Acid(b) Sulphurous
Acid(c) Sulphite Acid(d) Hydrogen Sulphide.
Answer: (b) Sulphurous Acid
Q17: Which gas is produced by reaction of base with metal ?(a)
Carbon dioxide(b) Dioxygen(c) Dihydrogen(d) Dinitrogen
Answer: (c) Dihydrogen
Q18: Acid + Metal-oxide ?(a) Base + Water(b) Salt + Water(c)
Base + Salt(d) Metal + Salt
Answer: (b) Salt + Water
Q19: Which of the following is a weak acid?(a) Hydrochloric
Acid(b) Nitric Acid(c) Acetic Acid(d) Sulphuric Acid
Answer: (c) Acetic Acid
Q20: An indicator is what type of compound?(a) reducing agent(b)
strong base or acid(c) weak base or acid(d) salt
Answer: (c) weak base or acid
Q21: Which of the following is strong acid ?(a) Acetic acid(b)
Citric acid(c) Nitric acid(d) Oxalic acid
Answer: (c) Nitric acid
Q22: Name the organic acid present in tomato(a) Tartaric Acid(b)
Malic Acid(c) Lactic Acid(d) Oxalic Acid
Answer: (d) Oxalic Acid
Q23: Fill in the blanks.(a) Turmeric, clove, rose petals are
______ _____ .(b) Acids ______ _______ bases to form ________ and
water.(c) The term pH was coined by _______ .(d) Turmeric turns
_____ _______ in basic medium.(e) ________ ________ is used in
softening water.(f) String acids show ______ ionisation while weak
acids show _______ ionisation.(g) Calcium Sulphate hemihydrate is
popularly known as _____ ___ _____.(h) Acids contain the hydrogen
(H+) as the only ______ _______.(i) Bases contain the Oxide (O2-)
or hydroxide (OH-) radical as the only _______ radical.
Answer:(a) Olfactory indicators(b) reacts with, salt (c)
Srensen(d) deep brown(e) Washing Soda(f) more, less(g) Plaster of
Paris(h) positive radical(i) negative Q24: List the organic acid
present in the following objects:(a) Citrus Fruits (lemon,
orange)(b) Sting of bees and ants(c) Rancid butter(d) Tamarind,
grapes, apples(e) Apples(f) Gastric juice(g) Vinegar(h) Fats(i)
Urine(j) Sour milk, curd
Answer: (a) Citrus Fruits (lemon, orange): Citric acid(b) Sting
of bees and ants: Formic acid(c) Rancid butter: Butryic acid (d)
Tamarind, grapes, apples : Tartaric acid(e) Apples: Malic acid(f)
Gastric juice: Hydrochloric acid(g) Vinegar: Acetic acid(h) Fats:
stearic Acid(i) Urine: Uric Acid(j) Sour milk, curd: Lactic
acid
Q25: State true () or false ()(a) Heat is evolved during
ionisation.(b) Solution of glucose in water produces ions.(c) Dry
ammonia has no effect on litmus paper.(d) Higher is the
concentration of H(aq), lower is the pH value.(e) The concentration
of aqueous solutions of acid, base and salt are generally expressed
in molarity.(f) pH of a solution can vary from 0-14.(g) HC1 is a
weak acid.(h) NaOH is a strong base.(i) Curd is alkaline in
comparison to fresh milk.(j) pH = + log10[(H3O-](k) Distilled water
does not conduct electricity.(l) Analgesics helps to relieve
acidity.
Answer:(a) Heat is evolved during ionisation. - True()(b)
Solution of glucose in water produces ions. False ()(c) Dry ammonia
has no effect on litmus paper. (True)(d) Higher is the
concentration of H(aq), lower is the pH value. True()(e) The
concentration of aqueous solutions of acid, base and salt are
generally expressed in molarity.True()(f) pH of a solution can vary
from 0-14.True()(g) HC1 is a weak acid. False ()(h) NaOH is a
strong base.True()(i) Curd is alkaline in comparison to fresh
milk.False ()(j) pH = + log10[(H3O-] False ()(k) Distilled water
does not conduct electricity. True()(l) Analgesics helps to relieve
acidity. False ()
Q26: Identify which of the following chemical formulas is acid,
base or salt. Write their corresponding chemical names also.(a)
HCl(b) NaOH(c) NaCl(d) Ca(NO3)2(e) Ca(OH)2(f) HNO3(g) NH4OH(h)
(NH4)2SO4(i) CuO(j) H2SO4(k) CuCO3(l) H2CO3(m) MgO(n) Mg3(PO4)2
Answer:(a) HCl - Hydrochloric Acid (b) NaOH - Sodium Hydroxide -
Base(c) NaCl - Sodium Chloride - Salt(d) Ca(NO3)2 - Calcium Nitrate
- Salt(e) Ca(OH)2 - Calcium Hydroxide(f) HNO3 - Nitric Acid (g)
NH4OH - Ammonium hydroxide - Base(h) (NH4)2SO4 - Ammonium sulphate
- Salt(i) CuO - Copper Oxide (j) H2SO4 - Sulphuric Acid(k) CuCO3 -
Copper Carbonate(l) H2CO3 - Carbonic acid(m) MgO - Magnesium
Oxide(n) Mg3(PO4)2 - Magnesium Phosphate
Q27: You have been provided with three test tubes. One of them
contains distilled water and the other two contain an acidic
solution and a basic solution, respectively. If you are given only
red litmus paper, how will you identify the contents of each test
tube?
Answer: The colour of red litmus paper changes to blue indicates
that the chemical is a base. If there is no change in colour, then
it is either acidic or neutral. We can easily identify a base.1.
Mark the three test tubes as A, B, and C. 2. Take a drop of the
solution A and put it on the red litmus paper. Repeat the same
process iwth solution B and C. 3. If any of them changes colour to
blue, then it is a base.And remaining two are acid and neutral. 4.
Now take a drop from the identified base and mix it with a drop
taken from the remaining two solutions separately. 5. Check the
drops of the mixtures on red litmus paper. 6. If the colour of red
litmus turns blue, then the second solution is neutral. If it does
not change colour, then the second solution is acid. This is
because acidic and basic solutions neutralize each other.
Q28: Why should curd and sour substances not be kept in brass
and copper vessels?
Answer: Curd and sour substances are acidic by nature. e.g. curd
contains lactic acid. When these substances are kept in metal
containers like brass and copper, metal react with acid and
liberate hydrogen gas and other harmful substances, which may spoil
these substances.
Q29: Why vinegar is used in pickling?
Answer: Vinegar contains an organic acid called acetic acid
(CH3COOH) which prevents the growth of micro organisms. Therefore
it is used in pickling.
Q30: Why phenolphthalein is considered acid base indicator?
Answer: It is because phenolphthalein turns pink in basic
solution whereas it remains unaffected in acid or neutral
solutions. It is able to differentiate between acid (colouless) and
base (pink colour).
Q31(NCERT): Which gas is usually liberated when an acid reacts
with a metal? Illustrate with an example. How will you test for the
presence of this gas?
Answer: Hydrogen gas is liberated when an acid reacts with a
metal.Take few pieces of zinc (Zn) granules in a delivery tube. Add
5ml of hydrochloric acid (HCl). White fumes will rise. Pass the gas
to a soap solution or collect it in a balloon (as shown in the
following video). The gas collected is Hydrogen gas. Since H2 gas
has lower density as compared to air, the balloon will float in
air.
Zn (s) + 2HCl (aq) ZnCl2(s) + H2 (g)
You can test the evolved hydrogen gas by its burning with a pop
sound when a candle is brought near the balloon (or soap
bubbles).
Q32(NCERT): Metal compound A reacts with dilute hydrochloric
acid to produce effervescence. The gas evolved extinguishes a
burning candle. Write a balanced chemical equation for the reaction
if one of the compounds formed is calcium chloride.
Answer: Since CO2 gas is liberated and the salt obtain has metal
Ca, it implies the reactant metal compound shall be a carbonate
i.e. CaCO3 The chemical equation is:
CaCO3 (s) + 2HCl (aq) CaCl2 (s) + CO2 (g) + H2O (l)Calcium
Carbonate + Hydrochloric Acid Calcium Chloride + Carbon Dioxide +
Water
Q33(NCERT): Why do HCl, HNO3 , etc., show acidic characters in
aqueous solutions while solutions of compounds like alcohol and
glucose do not show acidic character?
Answer: As aqueous solution, HCl and HNO3 dissociate into H+ and
Hydronium (H3O+) ions. HCl (aq) H+ + Cl- H+ + H2O H3O+
Although glucose and alcohol contain hydrogen, as aqueous
solution, they do not dissociate into ions and do not exhibit
acidic character.
Q34(NCERT): Why does an aqueous solution of an acid conduct
electricity?
Answer: The aqueous solution of an acid contains H+ and
Hydronium (H3O+) ions. Since ions carry extra charge and are able
to conduct electricity.
Q35: Why should acids be handled with care?
Answer: Acids have burning effect on our skin. They are
corrosive to living beings. Proper care must be taken while
handling acids in laboratory.
Q36: Why does dry HCl gas not change the colour of dry litmus
paper
Answer: Dry HCl gas does not form H+ions. It does not show its
acidic character. When in the aqueous solution, an acid ionizes to
form H+ions. In this case, neither HCl is in an aqueous form nor
the litmus paper is wet, therefore, the colour of the litmus paper
does not change.
Q37: While diluting an acid, why is it recommended that the acid
should be added to water and not water to the acid?
Answer: When diluting, the acid should always be added slowly to
water and in small amounts. Adding water to an acid is an
exothermic process, it can cause uncontrolled boiling and
splashing. That's why it is recommended that the acid should be
added to water and not water to the acid.
Q38: What is an amphoteric substance?
Answer: A substance is said to be amphoteric if it can behave
either as an acid or as abase. Water is the most common amphoteric
substance.
Q39: On the basis of origin, how acids are classified?
Answer: On the basis of origin, acids are classified as:1.
Organic acids 2. Inorganic or Mineral acids Q40: What are organic
acids? Give two examples
Answer: Acids obtained from living beings (plants and animals)
are called organic acid.e.g. citric acid present in fruits like
lemon, oxalic acid in tomato etc.
Q41: What are mineral acids? Give two examples
Answer: In general acids obtained from minerals or non-living
things are called mineral or inorganic acids. Examples are:
Sulphuric acid (H2SO4) Nitric Acid (HNO3) Q42: What is the chemical
name of Bleaching powder? How it is prepared? List its uses.
Answer:Chemical Name of Bleaching Powder: Calcium
OxychlorideChemical Formula: CaOCl2Preparation: It is prepared by
passing chlorine gas through dry slaked lime. Ca(OH)2+ Cl2 CaOCl2 +
H2O Slaked Lime + Chlorine Bleaching Powder + Water
Uses:1. As bleaching agent in textile industry. 2. As
disinfectant in water purification. 3. In paper industry to bleach
wood pulp. Q43: Which acid is used in Cola to give it a biting
sharp taste?
Answer: Phosphoric acid.
Q44: What is gypsum?
Answer: Plaster of Paris reacts with water to give a hard mass
called gypsum. (CaSO4)2. H2O (s) + 3 H2O (l) 2CaSO4.2H2O (s)
Plaster for Paris + Water Gypsum
Q45 Define Dilution.
Answer: Mixing an acid or base with water results in decrease in
the concentration of ions (H3O+/OH) per unit volume. Such a process
is called dilution and the acid or the base is said to be
diluted.
Q46(CBSE 2010): Tooth enamel is one of the hardest substance in
our body. How does it undergo damage due to the eating of
chocolates and sweets? What should we do to prevent it?orQ: Why
does tooth decay start when the pH of the mouth is lower than
5.5?
Answer: Tooth decay starts when the pH of the mouth is lower
than 5.5. Tooth enamel, made up of calcium phosphate is the hardest
substance in the body. It does not dissolve in water, but is
corroded when the pH in the mouth is below 5.5. Bacteria present in
the mouth produce acids by degradation of sugar (due to chocolates
and sweets) and food particles remaining in the mouth after eating.
The best way to prevent this is to clean the mouth after eating
food.
Using toothpastes, which are generally basic, for cleaning the
teeth can neutralise the excess acid and prevent tooth decay.
. Class 10 - Science - CH13 - Magnetic Effects of Electric
Current Magnetic Effects of Electric Current
Earth's Magnetic Field (computer simulation)credits:
wikipedia
MCQs, Q & A from CBSE Papers
Q1: The two poles in a magnet have(a) equal pole strength.(b)
unequal pole strength.(c) can be same or different(d) None of
these
Q2:A magnet AB is broken into two pieces. What is the polarity
of A, B, C and D?
(a) A, D: North & B,C: South(b) A, B: North & C,D:
South(c) A,C: North & B,D: South(d) A,D: South & B,C:
North
Q3: Magnetic field lines:(a) form closed curves(b) cannot
intersect(c) are crowded near poles(d) All of these
Q4: The correct field lines are:
Q5:Who had first observed the magnetic effect of an electric
current first ?(a) Faraday(b) Oersted(c) Volta(d) Ampere
Q6(NCERT): The magnetic field inside a long straight
solenoid-carrying current(a) is zero(b) decreases as we move
towards its end(c) increases as we move towards its end(d) is the
same at all points
Q7: With the help of which law the direction of a magnetic field
can be decided ?(a) Faraday's law(b) Fleming's right hand rule.(c)
Right hand thumb rule(d) Fleming's left hand rule.
Q8(NCERT): Which of the following property of a proton can
change while it moves freely in a magnetic field? (There may be
more than one correct answer.)(a) mass(b) speed(c) velocity(d)
momentum
Q9(NCERT): Which of the following correctly describes the
magnetic field near a long straight wire?(a) The field consists of
straight lines perpendicular to the wire.(b) The field consists of
straight lines parallel to the wire.(c) The field consists of
radial lines originating from the wire.(d) The field consists of
concentric circles centred on the wire.
Q10: What is the field line of a magnetic field passing through
the centre of current carrying circular ring ?(a) Circular(b)
Straight line(c) Ellipse(d) Magnetic field is zero at center.
Q11: Frequency of AC in India is(a) 50 Hz(b) 60 Hz(c) 110 Hz(d)
220 Hz
Q12: As we move away from a current carrying conductor, the
spacing between the magnetic lines of force(a) decreases(b)
increases(c) remains at equal distances(d) none of these
Q13(NCERT): A positively-charged particle (alpha-particle)
projected towards west is deflected towards north by a magnetic
field. The direction of magnetic field is(a) towards south(b)
towards east(c) downward(d) upward
Q14: Whose magnetic field is like a magnetic field of a bar
magnet?(a) Current carrying wire(b) Current carrying ring.(c)
Current carrying solenoid(d) Current carrying rectangular loop
Q15(NCERT): A rectangular coil of copper wires is rotated in a
magnetic field. The direction of the induced current changes once
in each(a) two revolutions(b) one revolution(c) half revolution(d)
one-fourth revolution
Q16: From which of the following case, the current in the loop
will not be induced ?(a) The loop is moved in the direction of the
magnet.(b) The magnet is moved in the direction of the loop.(c) The
loop and magnet are moved in the opposite direction with the same
speed.(d) The loop and magnet are moved in one direction with the
same speed.
Q17(NCERT): The phenomenon of electromagnetic induction is
(a) the process of charging a body.(b) the process of generating
magnetic field due to a current passing through a coil.(c)
producing induced current in a coil due to relative motion between
a magnet and the coil.(d) the process of rotating a coil of an
electric motor.
Q18(NCERT): The device used for producing electric current is
called a(a) generator.(b) galvanometer.(c) ammeter.(d) motor.
Q19(NCERT): The essential difference between an AC generator and
a DC generator is that(a) AC generator has an electromagnet while a
DC generator has permanent magnet.(b) DC generator will generate a
higher voltage.(c) AC generator will generate a higher voltage.(d)
AC generator has slip rings while the DC generator has a
commutator.
Q20(NCERT): At the time of short circuit, the current in the
circuit(a) reduces substantially.(b) does not change.(c) increases
heavily.(d) vary continuously.
Answers:1: (a) equal pole strength.2: (c) A,C: North & B,D:
South3: (d) All of these4: (a)5: (b) Oersted6: (d) is the same at
all points7: (b) Fleming's right hand rule.8: (c) velocity and (d)
momentum9: (d) The field consists of concentric circles centred on
the wire.10: (b) Straight line11: (a) 50 Hz12: (b) increases13: (d)
upward [hint: use Fleming's left hand rule]14: (c) Current carrying
solenoid 15: (c) half revolution16: (d) The loop and magnet are
moved in one direction with the same speed.17: (c) producing
induced current in a coil due to relative motion between a magnet
and the coil.
18: (a) generator.19: (d) AC generator has slip rings while the
DC generator has a commutator.20: (c) increases heavily.
Q21(CBSE 2010): What does the direction of thumb indicate in the
right-hand thumb rule?
Answer: Motion of the conductor.
Q22(CBSE ): Why does the acceleration of a bar magnet decreases
while falling through a solenoid, connected to a closed
circuit?
Answer: The induced current will exert an opposing force which
will reduce the acceleration of falling bar magnet.
Q23(CBSE): Can two magnetic lines of force ever interact?
Justify your answer. orQ(NCERT): Why dont two magnetic lines of
force intersect each other?
Answer: No. Two magnetic lines of force never interact. If they
did, it would mean that at the point of intersection, the compass
needle would point towards two directions, which is not
possible.
Q24(CBSE 2010): What will be the frequency of an alternating
current, if its direction changes after every 0.01 s?
Answer: If ac current changes its direct in 0.1s, it means it
completes its cycle in 0.2s(0.1s+0.1s). Frequency = 1/Time period =
1/0.02 = 50Hz.
Q25(CBSE 2010): AB is a current carrying conductor in the plane
of the paper as shown in figure. What are the directions of
magnetic field produced by it at points P and Q? Given r1 > r2,
where will the strength of the magnetic field be larger?
Answer: To know the direction of magnetic field produced by
current passing through a conductor, we can apply 'Right Hand Thumb
Rule' or Maxwell Corkscrew rule.At point P, the magnetic field
lines enter into the paper(screen). At point Q, the field lines are
coming out of paper (screen)
Magnetic field follows inverse square law i.e. a magnetic field
decreases inversely at a distance while moving away from the
conducting wire.Since r1 > r2, magnetic field is larger at Q
than P.
Q26: Name two sources of direct current and alternating
current.
Answer: DC source: dry cell, solar cell. AC source: AC dynamo,
turbines
Q27: What will happen to magnetic field due to a circular coil
carrying electric current, if the number of turns of the coil is
doubled.
Answer: The magnetic field produced by a current-carrying wire
at a given point depends directly on the current passing through
it. If the number of turns in the circular coil is doubled, the
field produced will also get doubled as that produced by a single
turn. This is because the current in each circular turn has the
same direction, and the field due to each turn then just adds
up.
Q28(CBSE 2011): Why does a current carrying conductor
experiences a force when it is placed in a magnetic field? State
Flemings left hand rule.
(Note: What happens when two bar magnets are kept close to each
other. They either repel or attract. It happens because the
magnetic field lines of the two interact each other. The answer for
the above question is also similar).
Answer: The current carrying conductor produce magnetic field.
When this conductor is placed in a magnetic field, it experiences a
force due to mutual interaction of these two magnetic fields.
Fleming's Left Hand Rule(credits:wikipedia)
Fleming's Left hand rule states, "When an electric current (I)
flows in a wire, and an external magnetic field (B) is applied
across that flow, the wire experiences a force (F) perpendicular
both to that field and to the direction of the current flow."
It can be represented by the left hand. Stretch the thumb,
forefinger and middle finger: of your left hand mutually
perpendicular to each other such that the fore finger points in the
direction of magnetic field and the middle finger in the direction
of current, then the thumb will point in the direction of motion or
the force acting on the conductor.
Flemings' Left Hand rule for electric motors Flemings' Right
Hand rule if for electric generators.
See also nice tutorial with beautiful graphics on Motors and
Generator by Florida State University.
Q29(NCERT/CBSE 2010/2011): List the properties of magnetic lines
of force.or
Q(CBSE 2011): (i) What is the direction of magnetic field lines
outside a bar-magnet ?(ii) Why two magnetic field lines cannot
intersect each other ?(iii) What is indicated by crowding of
magnetic field lines in a given region ?
Answer: Properties of magnetic lines of force are:1. The
imaginary lines which represent the direction of magnetic field,
are known as magnetic lines of force. 2. Magnetic lines of force
are closed curves. Outside the magnet their direction is from north
pole to south pole and inside the magnet these are from south to
north pole. 3. They neither have origin nor end. 4. These lines do
not intersect, because if they do so then it would mean two value
of magnetic field at a single point, which is not possible. 5. At
the poles of the magnet the magnetic field is stronger because the
lines of force there arecrowded together and away from the poles
the magnetic field is weak. Q30: When the current flows in a coil
in anti-clockwise direction, what pole does it create?
Answer: North Pole
Q31(CBSE 2011): What is the advantage of a.c. over d.c.?
Answer: The advantage of AC over DC is that electric power can
be transmitted over long distances without much loss of energy.
Q32: What does MRI stands for?Answer: Magnetic Resonance
Imaging.
Q33: What colour conventions are used in domestic electrical
wiring to indicate:(i) live wire(ii) neutral wire (iii) earth
wire
Answer: (i) live wire - red(ii) neutral wire - black(iii) earth
wire - green
Q34: State the principle on which an electric generator
works?
Answer: It works on the principle of electromagnetic induction.
It converts mechanical energy into electrical energy.
Q35: (i) What is a commutator?(ii) In an electric motor which
part act as commutator?(iii) How does it help?
Answer:(i) A device that reverses the direction of flow of
current through a circuit is called a commutator.
(ii) In electric motors, the split ring acts as a
commutator.
(iii) The reversal of current also reverses the direction of
force acting on the two arms and generates a torque. Therefore the
coil and the axle rotate half a turn more in the same direction.
The reversing of the current is repeated at each half rotation,
giving rise to a continuous rotation of the coil and to the
axle.
Q36: (i) What is an armature? What is its advantage?(ii) What
are the advantages of electromagnet over permanent magnet?
Answer: The soft iron core, on which the coil is wound, plus the
coils, is called an armature. It is used in electric motors to act
as an electromagnet. The armature (electromagnet) enhances the
power of the motor.(ii) The advantages are:1. You can turn the
electromagnet by switching ON or OFF the current. 2. You can
reverse the poles of the electromagnet by reversing the direction
electric current flow in the coil. 3. The magnetic field strength
can be changed by changing the amount of current in the coil. 4. An
electromagnet can easily be made more powerful than a permanent
magnet. Q37: Define electromagnetic induction. What are the
different ways to induce current in a coil?
Answer: The process, by which a changing magnetic field in a
conductor induces a current in another conductor, is called
electromagnetic induction.
We can induce current in a coil by applying any of the
following: (i) by moving it in a magnetic field (ii) by changing
the magnetic field around it.
Q38(HOTS): When a proton moves in a uniform magnetic field, why
does the momentum change but its kinetic energy does not change?
(Revisit MCQ Q8 above).
Answer: The magnetic force exerted will be perpendicular to the
direction of motion of the proton. As we know when when force
acting is perpendicular to the direction of moving charge, work
done will be zero. It means kinetic energy does not change. The
force is able to change the direction (velocity) of the proton but
not its speed (magnitude). Thus momentum and velocity changes.
Q39: Is magnetic field vector or scalar quantity?
Answer: Magnetic field is a vector quantity. It has both
magnitude and direction.
Q40: Can a 5A fuse be used in wire carrying 15 A current?
Why?
Answer: Since the current withdrawn in the electric circuit is
15A, the fuse will blow frequently and remain ineffective.
Q41(CBSE 2011/NCERT): An electric oven of 2 kW power rating is
operated in a domestic electric circuit that has a current rating
of 5A. If the supply voltage is 220V, what result do you expect ?
Explain.
Answer: Given, Power of the oven (P) = 2kW = 2 103 W Voltage
supplied (V) = 220V Current (I) = ? A Power = V I I = P/V = 2 103/
220 = 9.09 ASince the domestic electric circuit has a current
rating of 5A, the flow of 9.09 A by the Oven exceeds the safe
limit. Here, fuse will blow and break the circuit.
Q42: A current flows from the wire wound around an iron nail as
shown in the figure below. Where is the North Pole and South
Pole?
Answer: You may use right-hand rule i.e. if fingers of right
hand curl in the direction of the current, thumb points towards the
North pole. Top one will be South Pole and bottom face will be the
North Pole.
Q43(CBSE): What are the different ways to strengthen an
electromagnet?
Answer:1. Can add second battery to increase the amount of
current. 2. Add more number of turns in the coil. In addition, an
electromagnet also depends on the type of core used. Type of
material, shape, size and winding pattern of the coil also control
the shape and strength of the magnet field of an electromagnet.
Q44: A current of 5A is flowing through a conductor AB. Will the
current be induced in the circular wire of give radius 1m?
Answer: Since a steady current of 5A is flowing through the
conductor, no current or emf will be induced in the circular
wire.class 10 - Numericals on Light Reflection and Refraction
Numerical Problem on Light Reflection and Refraction (More
numerical and questions at this page) Q1: How fast does the light
travel in a glass of refractive index 1.5?
Answer:By Snell's law, refractive index (n) is the ratio of
i.e.
Q2:When a bright object is placed 10 cm away from a concave
mirror, its real image is formed at a distance 40cm from the
mirror. What is the focal length of the mirror?
Answer:
Q3: If the angle of incidence of a ray of light falling on the
glass surface is 30 and the angle of refraction is 19. what is the
refractive index of glass?
Ans: angle of incidence i = 30 angle of refraction r = 19
refractive index n = sin i/sin r = sin 30/sin 19 n = .5/.3256 =
1.535 ....(ans)
Q4: If a child crawls towards a mirror at a rate of 0.20 m/s,
then at what speed will the child and her image come nearby to each
other?
Ans: In 1 sec, the child moves towards the mirror by a distance
of 0.20 meters. In the same second, her image also moves 0.20m
closer.Therefore, the child and her image comes closer to each
other by 0.40m per second.
Q5: How many images will you see when two plane mirrors are
perpendicular to each other?Ans: The answer is three. You may see
practically as shown in the figure. You may follow the link on
multiple reflections to see more such images.
For two mirrors placed at any angle, the number of images formed
by the mirrors can be determined by:
N = (360/ ) - 1
where is the angle between the mirrors and N is the number of
images formed. For parallel mirrors = 0, hence N = . (You may have
seen this effect in barber shops).
Q6: A converging lens has a focal length of 15cm. An object is
placed 60cm from the lens. Determine the image.
Ans: Object Distance is u = -60cm focal length f = 15 cm
Lens formula is: 1/v - 1/u = 1/f 1/v = 1/15 + (-1/60) = 1/20 v =
20 cmThe image is real (+ve v) and is formed on the other side of
the lens.The magnification is: m = 20/-60 = -1/3The -ve sign of m
tells that the image is inverted. The magnitude of m
(magnification) is less than one, thus image formed is of reduced
size.
Q7: What is the focal length of a lens that produces a real
image three times as large as the object if the distance between
image and object is 1.0m?
Ans: magnification m = 3 Let u be the object distance, the image
distance will be v = 1-u Since image is real, we can assume it is a
convex lens. m = 3 = v/u = (1-u)/u u = -025cm and v = 0.75cm 1/v -
1/u = 1/f f = 18.75cm
Q8(*): At what value of the angle of incident 1 is a beam of
light reflected from the surface of water perpendicular to the
refracted beam? Assume n is the refractive index of the refracting
medium.
Answer: Let us try to draw a ray diagram to understand the
problem.
Let XY be the plane which separates the two media. The incident
ray AO gets reflected partly as OB and gets refracted as ray OC.
NOM is normal to the plane.
incident angle AON = 1reflected angle NOB = 2refracted angle COM
= 3
Since COB = /2 ...(given)1 = 2 ...(2nd law of reflection) This
gives 2 = /2 - 1
According to Snell's law (2nd law of refraction),n = sin i/sin r
= sin 1/sin 2 n = sin 1/sin ( /2 - 1)} n = sin 1/ cos 1$ n = tan 11
= tan-1 n
Q 9: Using mirror formula, compute the position of the object
placed in front of a concave mirror of focal length f so that the
image formed is of same size of the object. Answer: In this case,
magnification m = 1, since image size = object size (given).
Q10: Water has refractive index = 1.33 and air has refractive
index = 1.00. Find the critical angle for a water-air boundary.
Answer: Critical angle is considered when a ray of light travels
from denser medium to refractive medium.See the figure,
the angle of incidence i = c and r = 90Applying snell's law 1
sin c = 2 sin 90 1.33 sin c = 1.00 sin 90 sin-1 c = 0.752 c =
48.7
Q11 (NCERT): Find the focal length of a convex mirror whose
radius of curvature is 32 cm.
Answer: Given, radius of curvature = 32 cmFocal Length = radius
of curvature / 2 = 32 /2 = 16 cm
Q12(NCERT): A concave mirror produces three times magnified real
image of an object placed at 10 cm in front of it. Where is the
image located?
Answer: Given mirror = concave mirrorDistance of the object from
mirror = - u = - 10 cmDistance of the image from the concave mirror
= v?
Magnification (m) = -3
m = -v/u -3 = -v/-10 cm v = -3 10 = -30 cmThus image is formed
30 cm from pole in front of the concave mirror (-ve sign tells that
image formed is on the same side of the object).
(More numerical and questions at this page)Showing posts with
label 10th Electricity and Effects. Show all posts Showing posts
with label 10th Electricity and Effects. Show all posts08 April
2013CBSE Physics Numerical based on chapter - Electricity & its
effects For (Class X) NUMERICAL - Electricity and its effects For
(Class X)
1. 16. A resistance of 6 ohms is connected in series with
another resistance of 4 ohms. A potential difference of 20 volts is
applied across the combination. Calculate the current through the
circuit and potential difference across the 6 ohm resistance.2.
Calculate the number of electrons constituting one coulomb of
charge per second through any cross section of a conductor.3. How
much work is done in moving a charge of 2 C across two points
having a potential difference of 12 V ?4. How much energy is given
to each coulomb of charge passing through a 6 V battery ?5.
Calculate the work done in moving a charge of 5 Coulombs from a
point at a potential of 210 Volts to another point at 240 Volts.7.
When a particle of charge 10 C is brought from infinity to a point
P, 2.0 mJ work is done by the external forces. What is the
potential at P ?9. How many electrons pass through a lamp in one
minute if the current be 200 mA?10. Calculate the current supplied
by a cell if the amount of charge passing through the cell in 4
seconds is 12 C ?11. A 2 Volt cell is connected to a 1 resistor.
How many electrons come out of the negative terminal of the cell in
2 minutes?12. a) How much current will an electric bulb draw from a
220 V source, if the resistance of the bulb filament is 1200 ?b)
How much current will an electric heater coil draw from a 220 V
source, if the resistance of the heater coil is 100 ?13. The
potential difference between the terminals of an electric heater is
60 Volts when it draws a current of 4 Ampere from a source. What
current will the heater draw if the potential difference is
increased to 120 Volt.14. A torch bulb when cold has 1 resistance.
It draws a current of 0.3 Ampere when glowing from a source of 3 V.
Calculate the resistance of the bulb when glowing and explain the
reason for the difference in resistance. 15. A current of 0.2
Ampere flows through a conductor of resistance 4.5 . Calculate the
potential difference at the ends of the conductor. Paper for
formative assesmentsRelated search and topics10th science physics
Electric current and its effects Formative AssessmentsGuess Paper
SA-1- 2011 - X -Science-Electricity and its effects10th science
physics Electric current and its effects notes10th science physics
Electric current and its effects Solved questions (1-2 marks)10th
science physics Electric current and its effects Test
PaperNUMERICAL - Electricity & its effects For (Class X
unsolved)Solved Electricity numerical for class 10Current
Electricity Numerical solvedMCQ physics 10th Chapter Electric
current and its effectsElectric current and its effects: An
Introduction To Electrical Power And EnergyElectric current and its
effects: An Introduction To Electric Potential and Potential
DifferenceQUESTION BANK Class X Physics (Electricity)CBSE PHYSICS :
10th Electric Current & and Its Effect Multiple choice
questionsELECTRIC CURRENT AND CIRCUIT+ Revision NotesYou might also
like: NUMERICAL - Electricity & its effects For (Class X) X
Electric Current and Its Effect CBSE -1 Most Important Questions
Guess Paper SA-1- 2011 - X -Science-Electricity and its effects
Heating Effect of Electric Current and Electrical Power Linkwithin
Posted by J Sunil at Monday, April 08, 2013 0 comments Email This
BlogThis! Share to Twitter Share to Facebook Labels: 10th
Electricity and Effects, 10th Physics 25 May 2012Sadhana Devi
Vidyapith: Physics : Class X Chapter: ELECTRICITY Assignment ...
Physics : Class X Chapter: ELECTRICITY Assignment 2012-13
ASSIGNMENT -1, (2012-13) By JSUNIL Sub. Physics, Class - X
Chapter -ELECTRICITY One mark questions 1. Define the term electric
current.
2. Define the term resistivity of a material.
3. How is a Voltmeter connected in the circuit to measure the
potential difference between two points?
4. You have two metallic wires of resistances 6 ohm and 3 ohm.
How will you connect these wires to get the effective resistance of
2 ohm?
5. If the distance between two electric charges is doubled, how
much will the force exerting between them change to? Two marks
questions
6. State Ohms law. The resistance of a conductor is 1. What is
meant by this statement?
7. Why are coils of electric toaster made of an alloy rather
than a pure metal? 8. Why is...Read more
Related search and topics10th science physics : Termology :
Electric current and its effects10th science physics: Electric
current and its effects Formative AssessmentsGuess Paper SA-1- 2011
- X -Science-Electricity and its effects10th science physics
Electric current and its effects notes10th science physics Electric
current and its effects Solved questions (1-2 marks)10th science
physics Electric current and its effects Test PaperNUMERICAL -
Electricity & its effects For (Class X unsolved)Solved
Electricity numerical for class 10Current Electricity Numerical
solvedMCQ physics 10th ChapterElectric current and its
effectsElectric current and its effects:An Introduction To
Electrical Power And EnergyElectric current and its effects: An
Introduction To Electric Potential and Potential DifferenceQUESTION
BANK Class X Physics (Electricity)CBSE PHYSICS : 10th Electric
Current & and Its Effect Multiple choice questionsELECTRIC
CURRENT AND CIRCUIT+ Revision Notes10th Solved Science Sample
paperYou might also like: CBSE Physics Numerical based on chapter -
Electricity & its effects For (Class X) Guess Paper SA-1- 2011
- X -Science-Electricity and its effects NUMERICAL - Electricity
& its effects For (Class X) X Electric Current and Its Effect
CBSE -1 Most Important Questions Linkwithin Posted by J Sunil at
Friday, May 25, 2012 0 comments Email This BlogThis! Share to
Twitter Share to Facebook Labels: 10th Electricity and Effects 30
April 2012X MCQ based on Chapter Electricity MCQ OF ELECTRICITY
1.The rate of flow of an electric charge is known as :
(a) electric potential (b)electric conductance(c)electric
current (d)none of these
Ans : (c)electric current
2.The SI unit of electric current is :
(a)ohm (b)ampere (c)volt (d)faraday
Ans :(b)ampere
3.The instrument used for measuring electric current is :
(a)ammeter (b)galvanometer (c)voltmeter (d)potentiometer
Ans :(a)ammeter
4.The amount of work done in joules, when one unit electric
charge moves from one point to another point in an electric circuit
is called :
(a)electric current (b)electric resistance (c)electric
conductance (d)potential difference
Ans :(d)potential difference
5.The unit of potential difference is :
(a)volt (b)ohm (c)ampere (d)faraday
Ans :(a)volt
6.The relation between potential difference (V) and current (I)
is :
(a)V I2 (b) V 1/I (c) V2 I (d) V I
Ans :(d) V I
7.The relation between potential difference (V) and current (I)
was discovered by :
(a)Newton (b) Ampere (d) Volta
Ans : (c) Ohm
8.The obstruction offered by material of conductor to the
passage of electric current is known as :
(a)Resistance (b) Conductance (c) Inductance (d) None of
these
Ans : (a)Resistance
9.The SI unit of resistance is :
(a) Newton (b) Ohm (c) Watt (d) Joule Ans : (b) Ohm
17.Which of the following statement is not true, regarding the
electrical set-up for the verification of Ohms law:
(a) The voltmeter is connected in parallel with the known
resistance
(b) The ammeter is connected in series circuit(c) The rheostat
can only increase the resistance in electric circuit
(d)The single key is used to switch on/off the electric
circuit
Ans :(c) The rheostat can only increase the resistance in
electric circuit
18. A voltmeter is used to find p.d. in any electrical circuit
which of the statement given below is true :
(a) A voltmeter is a high resistance instrument and is connected
in series circuit
(b) A voltmeter is a low resistance instrument and is connected
in series circuit
(c) A voltmeter is a high resistance instrument and is connected
in parallel circuit
(d)A voltmeter is a low resistance instrument and is connected
in series circuit
Ans :(c) A voltmeter is a high resistance instrument and is
connected in parallel circuit
19. A battery of 12V is connected in series with resisters of
0.2 ohm , 0.3 ohm,0.4 ohm,0.5 ohm and 12 ohm. How much current
would flow through the 0.3 ohm resister
(a) 0.895A (b) 1.11A (c) 0.5A (d)none of these
Ans : (a) 0.895A20.Among which of the following resistance does
not depend : (a) length of conductor (b) area of cross-
section (c) temperature (d)density Ans : (d)density
10.In parallel combination of electrical appliances, total
electrical power
a. Increases b .Decreases c. Does not change d. Remain same.
11.The total work done by an electrical appliance during its
operation, is called electrical
a. Current b. Power c. Energy d. Potential
12.The number of joules in 1kWh is a.3.6x107 b.3.6x106 c.3.6x105
d.3.6x104
13.When electric current flows through a conductor, it
a. Gains electrons b. Loose electrons
c. Becomes hot d. No change is observed.
14.Heating of a current carrying conductor is due to
a. Loss of kinetic energy by atoms
b. Loss of kinetic energy by electrons
c. Attraction between electrons
D. Repulsion between electrons ; protons
15.The correct relation between heat produced &electric
current flowing
a. H I b. HI2 c. H1 /I d. H1/ I2
16.The relation between H ;I is called
a. Newton s law b. Faraday s law
c. Joules law d. Ohm s law
17.In electric heating appliances, the material of heating
element is
a. Brass b. Nichrome c. Silver d. Copper.
18. Formula for electric power is
a. P= V2 I b .P=V I c .P=I/V d. P=V/I.
19.Lamps of 40 watt&60 watt are connected in parallel, the
total power of combination is
a.40 watt b.60 watt c.24 watt d.100 watt
10.The resistance of a conductor is directly proportional to
:
(a) its area of cross-section (b) density (c) melting point (d)
length
Ans : (d) length
11.The resistance of a conductor is inversely proportional to
its :
(a) area of cross-section (b) length (c) specific resistance (d)
density
Ans :(a) area of cross-section
12.A current of 2A flows trough a conductor whose ends are at a
p.d of 4V. The resistance of the conductor is :
(a) 8 (b) 0.5 (c) 6 (d) 2
Ans: (d) 2
13.The rheostat is used in the circuit to :
(a) increase the magnitude of current only
(b) decrease the magnitude of current only
(c) increase or decrease the magnitude of current
(d) none of these
Ans :(c) increase or decrease the magnitude of current
14.During the verification of Ohms law :
(a) ammeter and voltmeter should be connected in series
(b) ammeter should be connected in series and voltmeter in
parallel
(c)ammeter should be connected in parallel and voltmeter in
series
(d) ammeter and voltmeter should be connected in parallel
Ans:(b) ammeter should be connected in series and voltmeter in
parallel15.Which of the following laboratory apparatus is not used
during the verification of Ohms law :(a) Voltmeter (b) Ammeter (c)
Galvanometer (d)Rheostat
Ans : (c) Galvanometer
See for more : (Practice) MCQ of Electricity
You might also like: Numericals On Motion test paper Solved
current electricity numerical for class 10 CBSE NCERT physics
Reflection and refraction MCQ solved X Human Eye and the Colourful
World (MCQ)Multiple choice questions Linkwithin Posted by J Sunil
at Monday, April 30, 2012 1 comments Email This BlogThis! Share to
Twitter Share to Facebook Labels: 10th Electricity and Effects 28
April 2012CBSE X Current Electricity Worksheet for CBSE Exam
Chapter: Current Electricity Worksheetby Jsunil Tutorial1.
Define electric current, state its unit, list the equation defining
electric current.2. List three types of energy that may be used to
produce current, and list three devices that provide this type of
energy.3. List three types of loads and list the energy conversions
taking place inside each one.4. What is the definition of voltage?
What is its unit?5. Prove that 1 J is equivalent to 1 Vx A x s.6.
How long does it take a current of 5.0 mA to deliver 15 C of
charge?7. What is the potential difference between two points if
1.0 kJ of work is required to move 0.5 C of charge between the two
points?8. What is the voltage of a source which provides 12.0 J to
each Coulomb of charge present?9. What is the energy of an electron
accelerated through a potential difference of 100.0 kV? (charge of
an electron 1.6 x 10-19Coulomb)10. What is the potential difference
between two points when a charge of 80.0 C has 4.0 x 10^3J of
energy supplied to it as it moves between the two points?11. There
is a current of 0.50 A through an incandescent lamp for 5.0 min,
with a voltage of 115 V. How much energy does the current transfer
to the lamp? What is the power rating of the lamp?12. If there is a
current of 2.0 A through a hair dryer transferring 15 kJ of energy
in 55 s, what is the potential difference across the dryer?13. An
electric drill operates at a potential difference of 120V and draws
a current of 6.0 mA. If it takes 45 s for the drill to make a hole
in a piece of wood, how much energy is used by the drill?14. An
electric toaster operating at a potential difference of 115 V uses
34 200 J of energy during the 20 sec it is on. What is the current
through the toaster?15. A motor draws a current of 2.0 A for 20.0
sec in order to lift a small mass. If the motor does a total of 9.6
J of work calculate the voltage drop across the motor.16. In a
lightning discharge, 30.0 C of charge moves through a potential
difference 108 V in 20 min. Calculate the current of the lightning
bolt.17. How much energy is gained by an electron accelerated
through a potential difference of 3.0 x 10^2 V?18. A 12V car
battery can provide 60.0 A for 1.0 h. how much energy is stored in
the battery?19. How much energy is required to dry your hair if the
hair dryer draws 12.0 A from a 110 V outlet for 12.0 min?Electric
Circuits:1. a) Describe the difference between current in a series
circuit and current in a parallel circuit.b) Describe the
difference between voltage in a series circuit and voltage in a
parallel circuit.2. Draw a schematic diagram of the following
circuit: One power source and a resistor are connected in series
with a combination of 3 light bulbs connected in parallel with each
other. Include a fuse, 4 switches, a voltmeter, and an ammeter. The
fuse should protect the whole circuit, one switch should shut off
the whole circuit and the other switches should control the
individual bulbs. The ammeter should read I and the voltmeter the
voltage of the resistor.3. a) What is a short circuit?b) Why is it
dangerous?c) Give two ways to protect against short circuits.4.
Describe the effect on the rest of the bulbs in problem two when
one burns out. Will the remainder glow brighter? dimmer? What will
be the effect on the source?5. Describe resistance, list 4 factors
affecting resistance.6. A conductor has a length of 2.0 m and a
radius of 3.0 mm. If the resistance is R = 100 S, calculate the new
resistance if the same material has:a) length = 6.0 m and r = 6.0
mmb) length = 1.0 m and r = 1.0 mm7. List two ways to increase the
current drawn by a circuit.8. Draw a graph of V-I for 2 resistors
and indicate which has the greatest resistance and why.9. A
voltmeter measures a voltage drop of 60.0 V across a heating
element while an ammeter reads the current through it as 2.0 A.
What is the resistance of the heating coil?10. How much current
flows through a 7.5 S lightbulb with a potential difference of 1.5
V?11. What is the voltage drop across an element which draws a
current of 5.0 A and has a resistance of 40 ohms?12. A set of 6
motors is connected in series to a 120 V source drawing 1.0 A of
current. Find:a) R totalb) R of each motorc) Voltage drop across
each load.13. Do resistors in parallel increase or decrease total
resistance?14. What resistance must be added in series to a circuit
containing a 33 ohm resistor in in order to draw 2.0 A of current
from a 120V source?15. How much energy is dissipated in 10 minutes
when a current of 4.0 A is flowing through a potential drop of 60.0
V?You might also like:
Guess Paper SA-1- 2011 - X -Science-Electricity and its ...
X Electric Current and Its Effect CBSE -1 Most Important ...
CLASS X solved questions -Magnetic effects of electric ...
NUMERICAL - Electricity & its effects For (Class X)
Linkwithin Posted by J Sunil at Saturday, April 28, 2012 1
comments Email This BlogThis! Share to Twitter Share to Facebook
Labels: 10th Electricity and Effects 18 April 2012Heating Effect of
Electric Current and Electrical Power CBSE PHYSICS By JSUNILHeating
Effect of Electric CurrentWhen charge (electron) move through
conductor ,collide with atoms of the conductors due to resistance
and transfer energy to the conductor which appear as heat .Hence
work done by electron to overcome resistance is equal to heat
generated in conductors.Let W work done to move Q charge through a
conductor of resistance R that appear as HeatW = H But , V = W/Q W
= Q V H = QV But, I = Q /t Q = It\ H = V I t Also, V = IR H = It x
IR H =I2Rt
Electrical Power:The rate of doing work in moving charge through
conductorsOR, The rate of producing heat in conductorOr, Rate of
producing electrical EnergyP = W/ tOR, P = H/t But, H =I2RtP = I2Rt
/t P = I2RAlso we may express Power as P = I x I x RUsing V =IRP =
VISI unit of POWERP = H/t = 1J/1Sec = WattIf 1oule energy consumed
by device in 1 sec Its power said to be 1 wattCommercial electrical
Energy unit is kWhWe know that P = H/t H = Pt If 1 kW (1000watt)
energy consumed for 1 hour It is called 1unit(BOT unit)Energy in
term of joule:H = 1kWh = 1000W x 3600sec =1000J/sec x 3600sec = 3.6
x 106 jNumerical X Current Electricity Numerical Practice
worksheetRead more You might also like: X Electric Current and Its
Effect CBSE -1 Most Important Questions Guess Paper SA-1- 2011 - X
-Science-Electricity and its effects CBSE Physics Numerical based
on chapter - Electricity & its effects For (Class X) CLASS X
solved questions -Magnetic effects of electric current Linkwithin
Posted by J Sunil at Wednesday, April 18, 2012 0 comments Email
This BlogThis! Share to Twitter Share to Facebook Labels: 10th
Electricity and Effects 15 March 2012X Electric Current and Its
Effect CBSE -1 Most Important Questions 1. How do we express
electric current?2. What is an electric circuit?3. What does a
switch do?4. Conventionally, in an electric circuit the direction
of electric current is taken as opposite to the direction of the
flow of electrons, which are negative charges. Why?5. What is the
SI unit of electric charge? How many electrons make one coulomb of
charge?6. Define the SI unit of current.7. Which instrument is used
to measure the current flowing in a circuit? How is it connected in
the circuit and why?8. In which smaller units can we measure the
small amount of current flowing in the circuit?9. How are the
related to the SI unit of current?10. What makes the electric
charge to flow?11. State the energy conversion taking place in (a)
Electric cell (b) Electric torch12. Define the electric potential
difference between two points in an electric circuit carrying some
current.13. Define the SI unit of Electric potential.14. Which
instrument is used to measure the electric potential difference
between two points in a circuit? How is it connected in the circuit
and why?15. State the law relating the potential difference across
a conductor and the current through it?16. The VI graph is a
straight line that passes through the origin of the graph. What do
you conclude from this observation?17. Define resistance of a
material. Define its SI unit.18. Which component is used to
regulate current without changing the voltage source in an electric
circuit?19. Fill in the blanks(a) A component of a given size that
offers a low resistance is a ________________. (b) A conductor
having some appreciable resistance is called a ______________. (c)
A component of identical size that offers a higher resistance is a
____.. (d) An _____________ of the same size offers even higher
resistance.20. Define the commercial unit of energy. Relate it to
joules.21. Discuss the activity to show that resistance of a
conductor depends on its length and area of cross section.22. What
is the electrical resistivity of the material of the conductor?
What is its SI unit?23. Which common factor affects both resistance
as well as resistivity and how?24. Alloys are commonly used in
electrical heating devices. Why?25. When a number of resistors are
connected in series in a circuit what would be their equivalent
resistance and why?26. When a number of resistors are connected in
parallel in a circuit what would be their equivalent resistance and
why?27. It is impracticable to connect an electric bulb and an
electric heater in series. Why?28. What is heating effect of
electric current. Name the various devices in which this effect is
utilized.29. State the Joules law of heating. Derive the expression
for the same.30. Which effect of current is responsible for the
glow of an electric bulb? Explain.31. The bulbs are usually filled
with few gases. Name those gases. Also discuss the cause for the
same.32. Which metal is used as the filament of an electric bulb
and why?33. How does a fuse work in the electric circuit?34. Which
materials are preferred for a fuse wire and why?35. Give the
ratings of various fuses used in the domestic circuit.36. Why is
Tungsten metal selected for making filaments of incandescent lamp
bulbs?37. A torch bulb is rated at 3V and 600mA. Calculate its a)
Powerb) Resistance c) Energy consumed if it is lighted for 4
Hrs.38. Which will offer more resistance a 50W lamp or 25W lamp
bulb and how many times?39. Why should the heating element of an
electric iron be made of iron, silver or Nicrome wire?40. If a wire
is stretched to triple its original length, what happens to its
resistively?41. Two identical resistors each of resistance 10 ohm
are connected 1) in series 2) in parallel, in line to a battery of
6volts. Calculate the ratio of power consumed in the combination of
resistors in the two cases.42. A bulb is rated at 220V- 100W. What
is its resistance? Five such bulbs burn for 4 hrs. What is the
energy consumed? Calculate the cost if the rate is 50paise per
unit?43. Two lamps rated 100W, 220V and 25W, 220V are connected in
parallel to 220V supply. Calculate the total current through the
circuit.44. A metallic coil connected to a 220V supply has a
resistance of 110 ohm. How long will it take this coil to heat 1kg
water from 2o0C to 700C? Assume whole heat produced by coil is
taken up by water. (Specific heat capacity of water = 4186 )45. Why
is much less heat generated in long electric than in filaments of
electric bulb?46. How does the resistance of wire change when 1)
Its length is doubled 2) Area is doubled?47. An electric kettle
rated 1000W, 220V is used to bring water at 20 degrees to its
boiling point. If the kettle is switched on for 10 minutes.
Calculate: a. The resistance of the element of kettleb. Current
flowing through the element c. Mass of water in the kettle.48. A
copper wire has a diameter of 0.5mm and resistively of . How much
of this wire is required to make a 10 ohm coil?49.A wire of
resistance 5ohm is bent in the form of a closed circle. What is the
effective resistance between the two points at the end of any
diameter of the circle?50. What is the effect on resistively of a
pure metal with the increase in temperature?