Chapter 8 Emagnet(Student)

8/12/2019 Chapter 8 Emagnet(Student)

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JPN Pahang Physics Module Form 5

Chapter 8: Electromagnetism

8.1: MAGNETIC EFFECT OF A CURRENT-CARRYING CONDUCTOR

Electromagnets

1. Conductor is a material that can flow ……………………..

2. Electromagnetism is the study of the relationship between ……………….and

………………..

3. ………………………. are produced by electrically charged objects.

4. A ar magnet produces the ………………………around it. raw the pattern of the

magnetic fields produced around a bar magnet below

!. "how the deflection of the pointer of the compasses .

#. $agnetic fields also can be produce by an electric current in a wire.

%. Electromagnet is a ………………… magnet. &t is made by winding a coil of insulated

wire round a soft iron core.

1

C!A"TER 8: E#ECTROMAGNETI$M

' "





(. )sing the diagram* complete the steps to switch on the magnetism effect.

Magnet%c F%el& &'e to a C'rrent %n $tra%g(t )%re

1. )sing R%g(t-(an& Gr%* r'le* draw the direction of current flows and pattern of magnetic

fields formed

2. +ight,hand -rip +ule states that the t('m of the right hand points to the direction of

current flow and the other +o'r c'rle& +%ngers points to direction of its ………………….

2

"oft iron core

&nsulatedwire

pins

C

supply

switch

"oft iron core

&nsulatedwire

pins

C

supply

switch

"witch isclosed





3. raw the same patterns from the top iews as follows together with the direction shown

by the compasses.

$eans that a wire carrying current ………….. the plane of paper

$eans that a wire carrying current …………... of the plane of paper

E,erc%se 8.1

1. /wo small plotting compasses 0 and are placed near a long straight wire carrying a current

as shown.

"how the directions shown by the pointers of the compasses

3





4. &n the diagram below* the compasses are put 'n&er the conductor. raw the direction

shown by compasses and what happen if the compasses are put on the conductor

Magnet%c F%el& &'e to a C'rrent %n a C%rc'lar Co%l

!. raw the direction of current flows and pattern of magnetic fields formed.

#. /he direction of magnetic field also can be determine using the R%g(t!an& Gr%* R'le.

4





Magnet%c F%el& &'e to a C'rrent %n a $oleno%&

%. $oleno%& is combination of coils of wire wounded around on some surface or wounded

around an iron core.

(. raw the direction of current flows* pattern of magnetic fields formed and direction by

the compasses.

. /o chec the poles formed* see from beside of the solenoid. &f the current flow is

cloc/%se* the polarity on that side is …………………… but* if the current flow is

ant%-cloc/%se* the polarity on that side is ……………………

Factors t(at a++ects t(e strengt( o+ an electromagnet15. /o study this* we need to carry out e6periments as follows. /he higher the number of paper

clips attracted to the solenoid shows the …………..….the strength of that electromagnet.

!

Paper clips

Iron core





Manipulated Responding Fixed

'umber of turns Current* types of core

'umber of paper clips attracted 'umber of turns* types of core

/ypes of core 'umber of paper clips attracted

Factors t(at a++ects t(e strengt( o+ an electromagnet

11. As a conclusion* fill the table below

Factors Conditions Number o paper clips

attracted

!ects on the strength o

electromagnetic ields

'umber of turns

Electric current

)se of normal iron,core

"nil")se of soft,iron core

A**l%cat%ons o+ Electromagnet

12. /here are many applications of electromagnets. 7abel and describe the figure of each

apparatus stated in the table below with its simple wor,frame.

1) Electric bells

2) Electromagnetic Relays

#

1.

2.

3.

4.

!.

1.

2.

3.

4.

switch





3) Telephone earpieces

%

1.

2.

3.

4.

!.

to





0 C%rc'%t reaers

2 #%+t%ng Magnet

(

&ts operate as …………………………

…………………………………………

…………………………………………

1.

2.

3.

4.

to from

&ts function to …………………………

…………………………………………1.

2.

3.

4.

3.





E,erc%se 8.1.3

1. A magnetic field is produced by the current in a long straight wire. /he strength of the magnetic

field increases if.

A /he magnitude of the current increases

8 /he distance from the wire increases

C /he length of the wire increases

2. 9hich of the following is tr'e about the magnetic field produced by a current in a flat circular

coil.

A &t is uniform inside the coil

8 &t is the weaest at the centre

C &t is the strongest at the centre

/here is no magnetic field outside the coil

3. 9hat is the effect of placing a piece of soft iron core inside a solenoid carrying current

A /he resistance of the solenoid decreases

8 /he current in the solenoid increases

C /he magnetic field becomes stronger

4. An electromagnet is used in these apparatus e,ce*t

A a compass

8 an a.c dynamo

C a moing coil ammeter

a telephone earpiece

!. 9hich electromagnet is the strongest

A 8 C

:2;, :2;, :4;, :4;,





4.3: Force Act%ng on a C'rrent-carr5%ng Con&'ctor %n a Magnet%c F%el&s

1. &f a current,carrying conductor is placed in a magnetic fields as shown in the e6periment* the

conductor will e6periences a …………………..

2. raw the combination <called catapult ield = of two electromagnetic fields below and show

the direction of moement of the conductor.

3. Flem%ng6s le+t-(an& r'le can be use to determine the direction of the force acting or the

motion of the conductor.

15

7

N $

N

Centre F%nger < =

$

F%rst F%nger < =

T('m < =

PowerSupply

C-Shapeiron

Magnet

Freely conductor

Long conductor

N





E++ect o+ T/o "arallel C'rrent-carr5%ng Co%ls %n a Magnet%c F%el&

4. &f two current,carrying conductor is placed in a magnetic fields as shown in the e6periment*

the conductor will e6perience ………………… or ………………….. force between them.

!. Complete the diagram for current with o**os%te direction flows in two parallel conductor

below>

#. Complete the diagram for current with same direction flows in two parallel conductor below>

11

/he two conductor will ……………….. to each other



CoilN

$

9

A 23

4

1

current

C

D

$agnet



T'rn%ng E++ect o+ a C'rrent-carr5%ng Co%l %n a Magnet%c F%el&

%. Consider a current,carrying coil A8C placed between the poles magnet as shown in the

figure below.

(. As the current flows through the coil from A to * an …... <1= force acts on the

arm C whereas a <3= force acts on the arms A8 according to

?leming@s 7eft and rule.

12

/he two conductor will ……………….. to each other



CoilN

$

9

A 23

4

1

current

C

D

N

$



. raw the catapult filed formed and draw arrows to show the moement of arms A8 and C.

D%rect C'rrent Motor

15. Complete the four stages of the motion of C motor below

13

egree > …………………………

Current flow > Bes 'o

…………….…………………..

Arm A8 > ……………………….

Arm C > …………………………

+otation > ………………………….

egree > …………………………


…..…………….…………………..

Arm A8 > ……………………….

Arm C > …………………………

+otation > …………… ……….

N $

A8 C



current

$

N

current

$

CoilN

current



Com*ar%son /%t( Alternat%ng C'rrent Motor

11. Complete the diagram of AC motor below>

14

egree > …………………………


…..…………….…………………..

Arm A8 > ……………………….

Arm C > …………………………

+otation > ……………

egree > …………………………


…..…………….…………………..

Arm A8 > ……………………….

Arm C > …………………………

+otation > …………… ……….





Factors t(at a++ect t(e s*ee& o+ rotat%on o+ an electr%c motor

12. /he magnitude of force acting on a conductor in a magnetic increases by>

i. &ncreasing the current flow

ii. "tronger magnet used

13. &n conclusion* the speed of rotation of the coil also can increased by>

i. …………………………………

ii. …………………………………

iii. …………….…………………………………

Mo;%ng Co%l Ammeter

1!

a.c supply





E,erc%se 8.3

1. /he motion of a conductor carrying

current in an magnetic fields can be

determine by

A +ight hand -rip +ule

8 ?leming@s +ight and +ule

C ?leming@s 7eft and +ule

irection of current flow

2.

A current carrying wire is in between the

poles of a magnet. /he direction of the force

on the wire is

A 'orth 8 East C

"outh 9est

1# ' "

'





3. /wo parallel wires are carrying eDual

currents in opposite directions. 9hich

diagram shows the forces ? on the

wires

A 8

C

4. /he function of the commutator in a

d.c. motor is

A to reerse the current in the coil at

eery half rotation

8 to enable the coil to be in electrical

contact with carbon brushes

C to preent the wires from entangling

!. A moing coil,ammeter is less

sensitie if

A the hair spring is harder

8 the magnet is stronger

C the scale is shorter

#. Choose the best pattern formed.

4.4: Electromagnet%c In&'ct%on

1. As we now* a steady magnetic field can be produced by a …………… or

………………………………….

2. 9hen we moe a coil without any current flow is in a magnetic field* an %n&'ce& e.m.+

<electromotie force= is produced.

3. An ……………………………… flows through the conductor and this phenomenon called

…………………………………

4. "o* electromagnetic induction reDuires relat%;e mot%on between magnet and the coil to

produce an induced current.

1%

? ?

? ?

?

?

??

??





!. Complete the table below as e6periment data for the diagram below>

In&'ce& e.m.+ 5 a mo;%ng con&'ctor

!ction #bsera$tion %nerence

/he wire is moed upwards -alanometer deflect to left

/he wire is moed downwards/he wire is moe horiontally

$agnet is moed upwards

#. Flem%ng6s R%g(t-(an& r'le can be use to determine the direction of the induction current

produced.

1(

T('m < =

Center +%nger < =

F%rst +%nger < =

G





In&'ce& e.m.+ 5 co%l

#en<6s #a/

%. 7en@s 7aw also can be use to determine the direction of induced current produced.

(. #en<6s #a/ states that the direction of the induced e.m.f is such that its magnetic effects

always …………………….the change producing.

1





Fara&a56s #a/ o+ electromagnet%c %n&'ct%on

. ?araday@s 7aw states that the magnitude of the induced e.m.f. is ……………………………..

to the rate of change of magnetic flu6 e6perienced by the conductor.

15. /he magnitude of the e.m.f in a wire increases when>

i. ……………………………………

ii. …………………………………….

iii. ………………..…………………………….

11. /he magnitude of the e.m.f in a coil increases when>

i. ………………………….……………………………………

ii. ……………………………………………………….

iii. ……….………………..…………………………….

A**l%cat%ons o+ electromagnet%c %n&'ct%on

25

9hen the ' pole ismoed towards the

coil* end of coil

becomes ..

9hen the ' pole

moed away from

the coil* end of coil becomes…………

…………..





12. A generator is basically the inerse of a motor. /here are many coils of wire wound that can

rotate in a magnetic field. /he a6le is turned by some mechanical such as …………………..*

………………………. or wind turbine.

13. /he dc generator and ac generator mae use of electromagnetic induction to produce

……………………………………

DC Generator

21





14. raw the graph of output current from the dc generator aboe.

22

9hen coils is at its horiontal position

…………………

...........................

9hen coils is at its ertical position

……………… ……………..

………………





AC Generator

1!. raw the graph of output current from the ac generator aboe

1#. /he magnitude of the output oltage increases when>

i. ………………….……………………………………

. ……………………………………………………….

i. ……….………………..…………………………….

23





24

9hen coils is at its horiontal position

…………………

...........................

'o changes of magnetic flu6

'o e.m.f is induced

hen coils is at its ertical position

…………… ……………..

……………

9hen coils is at its ertical position

……………… ……………..

………………





Alternat%ng an& &%rect c'rrent =a.c>&.c

1%. Complete the table of comparison below.

AC C'rrent DC C'rrent

&raphs

'irection

Examples o sources and symbols1.

2.

3.

1.

2.

3.

2!

/ime* ts/ime* ts

Current* &A

/ime* ts/ime* ts

Current* &A

Current* &A

Current* &A





E,erc%se 8.4

1. 9hich of the following is an e6ample

of induced magnetism

A. A compass needle pointing north

8. A north pole attracting iron fillings

C. A north pole repelling a north pole

. A coil of a motor tuning in magnetic

field

2.

/he diagram shows a coil in magnetic

field. &f we want to mae a a.c generator*

what should to be connected to F and B

A. d.c. supply

8. "lips rings

C. "oft,iron core

. "plit rings commutator

3.

4. 9hich of the following represent the

output oltage of an a.c generator

A.

8.

C.

2#





.

4.0: Trans+ormers

1. &n $alaysia* our electricity for domestic supplied at a oltage of ……………… a.c.

2. oweer* most of home appliances at home use lower than or higer than 245;.

3. /ransformers are found in many deices such as ……………….* ………………….*

………………….. and etc.

4. /he main use of transformer is to conert ……………………. AC ;oltage to …………….

one or ice,ersa.

O*erat%ng *r%nc%*le o+ a trans+ormer

!. Complete the diagram below

#. 9hen an alternating current flows in primary coil* and ………………………….. is produced

in the soft iron core.

%. $agnetic flu6 linage to ……………………. coil and will cut the magnetic fields lines.

(. /he secondary coil e6periences the rate of change of magnetic field and …………………. is

induced in secondary coil. <induced e(m( =

2%





. 9hen the current in primary coil decreases* the magnetic field will ………………… and

again cut the secondary coil.

15. An e.mf acting in the opposite direction is induced in the secondary coil.

11. ence* an ……………………….. of the same freDuency is induced in the secondary coil.

12. /he output oltage is depends on the ………………. of number of turns of primary and

secondary coils.

$te*-'* an& ste*-&o/n trans+ormers

13. /he relationship between the ;oltages and the rat%o of the turns in primary and secondary

coils can be write as below.

14. &f Ns is greater than Np* then )s is ………………… than )p. /he type of transformer is

………………………….

1!. &f Ns is less than Np* then )s is ………………… than )p. /he type of transformer is

………………………….

1#. ?or e6ample* if the turns ratio is 1>!5* the output oltage is stepped down ……….. times.

1%. &f we consider an %&eal trans+ormer* there is no loss of energy.

2(

OR

0rimary oltage

"econdary oltage

'umber of turns in primary coil

'umber of turns in secondary coil





Energ5 losses %n a trans+ormer

1(. As we now* an %&eal trans+ormer has ………….. effiency.

1. 8ut in practice* the efficiency of a tranformer is …………….. 155G.

25. /he effiency of a transformer is e6pressed as follows>

21. Complete the table below>

*ype o losses Causes +ay to reduce• Changing of magnetic field induced current

in soft iron core

•

•

eat loss • As the number of turn increases* the

resistance of conductor also increases.

• .

•

• /he core is magnetied and demagnetied

alternately due to a.c current in primary coil

•

•

•

2

Comparing with the

transformer eDuation

155G

155G

Pout

Pin

)s%s

)p%p

η = ×

= ×





?lu6 leaage • 7eaage of magnetic flu6 in the primary coil •

E,erc%se 8.0

1. "oft iron core is used as the

transformer core becauseA. "oft iron core has low resistance

8. "oft iron becomes a permanent magnet

C. "oft iron is easily magnetied and

demagnetied

. "oft iron is better conductor than steel

2. 9hich of the following is correct

about step,down transformer

A. /he output oltage is higher than input

oltage

8. the output power is greater than input

power

C. /he output current is greater than the

input current

3. All the four transformer gien below

hae the same input oltage. /he

number of turns in the primary coil and

secondary coil are N, and N-. 9hich

has the highest output oltage

N, N-A 12555 24555

8 #5 1255

C #555 2555

1255 255

4. /he number of turns between each pair

of output terminals of a transformer is

shown in the diagram. 8etween which

terminal the output is 12 ;

A. 0 and

8. and +

C. + and "

. 0 and +

35





!. 9hen primary coil of an ideal

transformer is connected to 12 ; a.c

supply* the current is 2.5 A. &f the

output oltage is 455 ;* what is the

current in secondary coil

A. 5.5# A

8. 5.#5 A

C. #.#% A

. ##.% A

#. A transformer only can wor with

A. d.c supply

8. a.c supply

C. dry cells

. electrolyte cells

4.2: Generat%on an& Transm%ss%on o+ Electr%c%t5

$o'rces o+ Energ5

1. /he generation of electricity comes from many sources such as >

a. …………………………

b. ………………………....

c. …………………………

d. …………………………

e. …………………………

f. …………………………

g. …………………………

h. …………………………

Transm%ss%on o+ Electr%c%t5

2. Electricity can be supply either from ………….. or a(c source.

3. /he circuit diagram below shows a sample of the transmission of electricity from

…………… source. raw the current flow on the circuit diagram.

31

bulb





4. /he diagram below shows a sample of the transmission of electricity from ……………

source.

Nat%onal Gr%& Net/or

!. 'ational -rid 'etwor is a networ of underground cables or …………… which connect all

the power stations and substations for the whole country.

#. /his networ starts at electrical power plant lie Chenderoh 7ae 0ower "tation which is

hydroelectric power station* and end at our houses.

%. Complete the diagram below by showing the cables of transmission and suitable users.

32

Step-uptransformer

Step-downtransformer

0ower plant

33 ;

transmission

Heavyindustry

Lightindustry

uildings

My house





(. Electrical energy is transmitted from the power station to the consumer using long

transmission cables.

. /his will bring to power loss as ………… energy. 0ower loss can be calculate as follow>

2

heat P % R=

15. /he power loss can reduce by>

i. +educing the ……………………… of the cables

ii. +educing the current or ……………………. the oltage in the cable.

Rene/ale energ5

11. Energy plays a ery important role in economic deelopment but the reseres of fossil fuels

such as oil and gas are ery limited.

12. ence* there is modern trend of the nations that is to harness the rene/ale energ5.

13. +enewable energy sources are continually replenished naturally means they are sustainable.

14. -ie the e6ample of rene/ale energy>

i. ……………………………

ii. ……………………………

iii. ……………………………

i. ……………………………

. ……………………………

i. ……………………………

ii. ……………………………

1!. -ie the e6ample of non-rene/ale energy>

i. ……………………..

33

& H current flows in the cable+ H resistance of the cable





a= …………………..

b= ………………….

c= …………………..

1#. -ie the benefits of using the renewable energy to our nation>

i. ………………………………………………………………………

ii. ………………………………………………………………………

iii. ………………………………………………………………………

i. ………………………………………………………………………

- En& o+ C(a*ter 8 -

E,erc%se 8.2

1. 9hich of the following is not a

renewable energy source

A. 9ind

8. "olar

C. Coal

. 8iomass

2. /he major source of energy for

electrical generation in $alaysia is

A. 'atural gas

8. 9ind

C. hydro

3. 9hich of the following is an

adantage of using wind energy for

generation of electricity

A. &ts aailable all the time

8. &ts easy to use

C. &ts cheap to use

. &t@s a renewable energy

4. 9hich of the following is an

adantage of 'ational -rid 'etwor

A. Electrical power breadown can be

countermeasure immediately

8. 7oss of power can be reduce

C. &ts using less cables

. &t@s a renewable energy

!. &n the transmission of electricity* the

most effectie mean to reduce power

loss in the transmission cable is by

A. )sing copper cables

34





8. /ransmission at high oltage

C. using alternating current

. )sing thic cables

For .uestion / and 0

#. A power station generates !55 9 of

power at #55 ;. An ideal transformer

steps up the oltage to 132 ; for

transmission.

9hat is the ratio of the number of turns in

the secondary coil of the transformer to

that in primary coil

A. 1>22

8. 22>1

C. 1>225

. 225>1

%. &f the resistance of 1 m of the cable is

2 Ω* what is the power loss from each

m length of cable

A. 3 9

8. 1# 9

C. 2# 9

. 2 9

Re%n+orcement C(a*ter 8

"art A: O?ect%;es @'est%ons

1. 9hich diagram best shows the pattern of

field lines around a bar magnet

A.

8.

C.

.

2. 9hich materials are suitable to mae the

core of an electromagnet

Core o an electromagnet

A &ron

8 "teel

C 9ood

Cuprum

3!





3. +efer to the diagram aboe* when the

switch is close* the pointer of the compass

will point to

A. "tay at 'orth

8. East

C. 9est

. ;ibrate at its place

.

4. A straight wire carrying a current produces

a magnetic field. 9hich diagram shows

the correct shape of the field

A.

8.

C.

.

.

!. A student carries out an e6periment to see

the effect of a magnetic field on a wire

carrying a current. /he wire moes

upwards as shown. 9hat should thestudent do to mae the wire moe

downwards

3#

cardboardwire

compass

'

E

9





A. Change the direction of the current

8. $oe the poles closer

C. "end a smaller current through wire

. )se stronger magnet

#. 9hen electricity is transmitted oer long

distances* energy is wasted. ow can the

wasted energy be ept as small as

possible

.

A. Ieep the current in the transmission lines

as large as possible

8. Ieep the power supplied to thetransmission lines as large as possible

C. Ieep the resistance of the transmission

lines as large as possible

. Ieep the oltage supplied to the

transmission lines as large as possible

%. /he diagram shows a transformer

9hat is the oltmeter reading

A. 1.2 ;

8. 12 ;

C. 125 ;

. 1255 ;

(. 9hich two electrical Duantities are

measured in olts

A. current and e.m.f

8. current and resistance

C. e.m.f and potential difference

. potential difference and resistance

. /he figure shows an electromagnet.

/he strength of the magnetic field can be

increase at point + by

& increasing the number of turns of the coil

&& reducing the resistance of the rheostat

&&& bringing the electromagnet closer to 0

A. & and && only8. & and &&& only

C. && and &&& only

. &* && and && only

3%

J +





.

15. /he diagram shows a solenoid connected

to a sensitie oltmeter. 9hich of the

following would gie a ero reading on the

oltmeter

A. olding the magnet stationary inside the

solenoid

8. $oing the magnet away from the

solenoid

C. $oing the magnet towards the solenoid

. $oing the solenoid towards the magnet

.

11. /he diagram shows a transformer with an

alternating oltage of 155 ; applied to the

primary coil. 9hat is the output oltage

A. !5 ;

8. 155 ;

C. 255 ;

. (55 ;

12. 9hich graph shows the output oltage

from a simple a.c. generator

A.

8.

C.

.

.

13. A transformer has !5 turns on its primary

coil and 155 turns on its secondary coil.

An a.c. oltage of 2!.5 ; is connected

across the primary coil. 9hat is the

oltage across the secondary coil

3(





A. 12.! ;

8. !5.5 ;

C. 1%! ;

. 255 ;

.

14. /wo circuits are set up as shown. /he iron

rods are placed close together* and are free

to moe.

9hat happens to the sie of the gap at F when

switch " is closed

A. &t decreases

8. &t decreases then increases

C. &t increases

. &t does not change

1!.

0+" is a cuprum wire put horiontally on a

table. F and B are two compasses put on the

wire. 9hat will happen to the compasses

when switch " is closed

A. 8oth compasses point to East

8. 8oth compasses point to 9est

C. 8oth compasses pointer unchange

. Compass F pointer unchanged but

compass B point to East.

1#.

iagram shows an electromagnet 0+. /he

poles for 0+ are

0 +

A 'orth "outh "outh8 "outh 'orth 'orth

C "outh 'orth "outh

'orth "outh 'orth

3

'







a= <i= 9hat is the core made of

…………………………………………………………………………

<ii= "tate the polarity at end X when the switch is closed

…………………………………………………………………………

b= 9hen the switch is closed* it was found a number of pins was attracted to end X.

<i= "uggest one way to &ecreas%ng the number of pins attracted to end X

…………………………………………………………………………

<ii= 9hat will happen to the pins at end X when the switch is o*en

E6plain your answer.

…………………………………………………………………………

2. ?igure 2 shows an alternat%ng c'rrent generator.

a= <i= 'ame the phenomenon used to produced an e.m.f in the coil.

……………………………………………………………......

<ii= 9hat is the effect on the current produced if the magnets are moed further apart from

each other -ie a reason.

…………………………………………………………………………………………….

…………………………………………………………………………………………….

b= ?igure 3 shows the graph of the output current against time.

41

Current* &A





i. "tate the alue of the pea current.

……………………………………………….

ii. Calculate the freDuency of the alternating current.

………………………………………………..

iii. Kn the same a6es* setch the graph output current against time if the coil is now

rotated at twice the speed.

c= 9hat are the changes that need to be made to conert this generator to a direct current

motor

…………………………………………………………………………………………………

…………………………………………………………………………………………………

3. ?igure shows a magnet which is pushed towards a solenoid.

42

,2

5.54

/ime* ts5.5(

2





a= "tate the magnetic poles of the two ends* 0 and of the solenoid when the magnet is moed

towards the solenoid* stationary inside the solenoid and then moe away from the solenoid.

……………………………………………………………………………………………………

……………………………………………………………………………………………………

……

b= "tate the 7en@s 7aw

……………………………………………………………………………………………………

……………………………………………………………………………………………………

……

c= "uggest three ways to mae the deflection angle of the -alanometer to become bigger.

………………….…………………………………………….

………………….……………………………………………..

………………….……………………………………………..

d= 'ame four essential parts of an a.c generator

………………………………………………

……………………………………………..

……………………………………………….

………………………………………………..

43

"@

Gal;anometer





"art C: Essa5 @'est%ons

1. /he transmission of electrical energy from a power station to factories and houses is by means of

a system called 'ational -rid 'etwor.

a= "tate the transformation of energy in a hydroelectric power station.

b= E6plain what is meant by 'ational -rid 'etwor and state three adantages of its

distribution of electrical energy.

c= ?igure 4 below shows a model for transmission of electrical power using source of 12 ; a.c.

Bou are supposed to set up the model by using the information in the table below>

Number o turns o coils *ypes o transormers Material o transmission cables

1255 "olid copper core Constantan

#55 7aminated soft,iron core Copper

#5 7aminated copper core 'ichrome

45 9ooden core /ungsten

i. Choose the number of turns of primary and secondary coil for step,up transformer.

-ie a reason.

ii. Choose the type of core of the step,up and step,down transformer. -ie a reason.

iii. Choose the type of material of transmission cables. -ie a reason.

d= &f the resistance of the transmission cable in the model is 25 Ω* calculate

i. the current that flows through the transmission cable

ii. the power loss due to heating effect of the transmission cable

44

12 ; a.c

source 245 ; 245 ; 12 ;12 ; bulb

is bright

/ransmission wire





2. iagrams show wire coils connected to the ammeters* switches and d.c power supply

9hen the switch is on and iron filings of the same amount is spread on each of the cardboard

surface* the pattern of the iron fillings is formed as shown in the diagrams.

a= 9hat is meant by magnetic field

b= )sing diagrams aboe* compare the number of turn of the coils* the pattern of the iron

fillings and the angle of deflection of the ammeter indicator.

4!





c= "tate the relationship between the strength of the magnetic field and

i. the pattern of iron fillings

ii. the number of turn of the coils

d= iagram shows two thin copper strips* 0 and +"* connected ia circuit. E6plain what

happens to 0 and +"* when the switch is on.

4#

0

"77





3. A student used the apparatus shown in figure below to inestigate electromagnetic induction. /he

magnet will be drop inside the coil. e obsered that the angle that the pointer of the

galanometer deflects become increase when he increase the number of turns on the solenoid.

a= ?rom the aboe obseration* mae a suitable inference

b= "tate one appropriate hypothesis that could be inestigated

c= esign an e6periment to inestigate the hypothesis that you stated in <b=. &n your description*

state clearly the following>

i. Aim of e6periment

ii. ;ariables in the e6periment

iii. 7ist of the apparatus

i. Arrangement of the apparatus

. 0rocedures of the e6periment on controlling the manipulated and responding

ariables

i. /abulation of the result

ii. Analysis of the result

iii. "tate one precaution in the e6periment

G G

Chapter 8 Emagnet(Student)

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