Electricity- physics class 10

ELECTRICITY

CONTENT

INTRODUTION

ELECTRIC CHARGE AND ITS PROPERTIES

CONDUCTORS AND INSULATORS

ELECTRIC CURRNT

POTENTIAL DIFFERENCE

OHM’S LAW

RESISTANCE IN SERIES AND PARALLEL

HEATING EFFECT OF ELECTRICITY AND ITS APPLICATION

INTRODUCTION

Electricity is probably the eighth wonder of the modern civilized world . Its discovery and utility have revolutionized the industries and home of the civilized world . Life today is totally dependent on it .

Electricity is one of the form of energy and it can be produced from other types of energy . Its great advantages over all other type of energy are it :

1. Cleanness

2. Flexibility

3. Efficiency

4. Easier Transmission

ELECTRIC CHARGE AND ITS PROPERTIES • Charges – Property of an object by virtue object which it

applies force on another objet is called charge .

The S.I. unit of charge is coulomb. An electron posses a negative charge of 1.6 × 10−19.

• Properties

1. Unlike charges attract each other and like charges repel each other .

2. Electric charge is conserved .

3. Electric charge is additive .

4. The forces between two charges varies directly as the product of two charges and inversely as the square of the distance between them .

𝐹 = 𝑘𝑞1 𝑞2𝑟2

CONDUCTORS AND INSULATORS

Conductors -These substance have the property to conduct electricity through them. These have free or loosely held electrons which helps in conducting electricity. Example – copper.

Insulators -These substance have the property to obstruct the flow of electricity. These do not have free electrons present in them. Example –Rubber Insulation.

ELECTRIC CURRNT• Electric current – it is defined as the rate of flow of electric

charges .

S.I.Unit – Ampere .

Formulae - 𝐼 =𝑄

𝑇or 𝑄 = 𝐼𝑇

• 1 ampere – current flowing through a conductor is said to 1 ampere if one coulomb of charge flows through it in one second .

1 𝑎𝑚𝑝𝑒𝑟𝑒 =1 𝑐𝑜𝑙𝑜𝑢𝑚𝑏

1 𝑠𝑒𝑐.

POTENTIAL DIFFERENCE

Potential difference :- between two points A and B of a conductor is the amount of work done to move a unit charge from A to B.

𝑃𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 =𝑊𝑜𝑟𝑘 𝐷𝑜𝑛𝑒

𝑐ℎ𝑎𝑟𝑔𝑒

The SI unit of potential difference is volt (V).

One volt is the potential difference when 1 joule of work is done to move a charge of 1 coulomb from one point to the other.

OHM’S LAW• Ohms law is a relationship between the potential

difference across a conductor and the current flowing through it.

• Ohm’s law states that :-

“The current flowing through a conductor is directly proportional to the potential difference between its ends provided its temperature remains constant”

𝐼 ∝ 𝑉 or R =𝑉

𝐼

Where R is a constant called resistance for a given metallic wire at a given temperature.

RESISTANCE IN SERIES

When three resistors R1, R2 and R3 are connected in series across AB

• i) The current in all the resistors is the same.

• ii) The total voltage (PD) across the resistors is equal to the sum of the voltage across each resistor.

V = V1 + V2 + V3

• iii) The equivalent resistance is the sum of the resistances of each resistor.

RS = R1 + R2 + R3

RESISTANCE IN PARALLEL• When three resistors R1, R2 and R3 are connected in

parallel across AB,

i) The voltage (PD) in all the resistors is the same.

ii) The total current in all the resistors is the sum of the current in each resistor.

I = I1 + I2 + I3

iii) The reciprocal of the equivalent resistance is the sum of the reciprocals of each resistance.

HEATING EFFECT OF ELECTRICITY AND ITS APPLICATION

Joule’s law of heating Let An electric current I is flowing through a resistor having resistance equal to R. The potential difference through the resistor is equal to V. The charge Q flows through the circuit for the time t. Thus, work done in moving of charge Q of potential difference V = VQ Since, this charge Q flows through the circuit for time t.

The heat produced in wire is directly proportional to i. Square of current. ii. Resistance of wire. iii. Time for which current is passed.

𝐻 = 𝐼2 𝑅𝑇

Applications of heating effect of electric current

There are many practical uses of heating effect of current. Some of the most common are as follows. • An incandescent light bulb glows when the filament is

heated by heating effect of current, so hot that it glows white with thermal radiation (also called blackbody radiation).

• Electric stoves and other electric heaters usually work by heating effect of current. •

• Soldering irons and cartridge heaters are very often heated by heating effect of current.

• Electric fuses rely on the fact that if enough current flows, enough heat will be generated to melt the fuse wire.

An incandescent light bulb

• Electronic cigarettes usually work by heating effect of current, vaporizing propylene glycol and vegetable glycerin.

• Thermistors and resistance thermometers are resistors whose resistance changes when the temperature changes. These are sometimes used in conjunction with heating effect of current(also called self-heating in this context): If a large current is running through the nonlinear resistor, the resistor's temperature rises and therefore its resistance changes. Therefore, these components can be used in a circuit-protection role similar to fuses, or for feedback in circuits, or for many other purposes. In general, self-heating can turn a resistor into a nonlinear and hysteretic circuit element

THANK YOU

• Made by :- Amit Choube

Class :- 10th B