Electric Resistance and Ohm’s Law Nootan Solutions, ISC Class-12 Physics Nageen Prakashan Chapter-5 Solved Numericals. Step by step Solutions of Kumar and Mittal ISC Physics Class-12 Nageen Prakashan Numerical’s Questions. Visit official Website CISCE for detail information about ISC Board Class-12 Physics.

Class: 12
Subject: Physics
Chapter 3:

## Electric Resistance and Ohm’s Law

 Board ISC Writer /Publications Nootan / Nageen Prakashan/Kumar and Mittal Topics Solved Numericals of page 221,222,223,224

#### Definition of Electrical Conductivity

It is the inverse of specific resistance for a conductor whereas the specific resistance is the resistance of unit cube of the material of the conductor.

#### SI Unit of Conductivity:

The SI unit of conductivity is mhom-1

#### Electrical Conductivity

When a conducting substance is brought under the influence of an electric field  ,free charges (e.g. free electrons in metals) move under the influence of this field in such a manner, that the current density  due to their motion is proportional to the applied electric field.

#### Significance of Ohm’s Law:

Ohm’s law is obeyed by many substances, but it is not a fundamental law of nature. It fails if

1. V depends on I non- linearly. Example is when ρ increases with I (even if the temperature is kept fixed).
2. The relation between V and I depends on the sign of V for the same absolute value of V.
3. The relation between V and I is non- unique. For e.g., GaAs

#### Kirchhoff’s First Rule:

At any junction of several circuit elements, the sum of currents entering the junction must be equal the sum of currents leaving it.

In the above junction, current I enters it and currents I1 and I2 leave it. Then, I = I1 + I2.
This is a consequence of charge conservation and assumption that currents are steady, that is no charge piles up at the junction.

#### Kirchhoff’s Second Rule:

The algebraic sum of changes in potential around any closed resistor loop must be zero. This is based on the principle that electrostatic forces alone cannot do any work in a closed loop, since this work is equal to the potential difference, which is zero, if we start at one point of the loop and come back to it.

### Nageen Prakashan Chapter-5 Solved Numericals of Electric Resistance and Ohm’s Law Nootan Solutions Kumar and Mittal, ISC Class-12 Physics

( Page – 221 )

Question 1

A current ………………….the wire .

Question 2

A current ………………………..conductor

(i)………………………

(ii)……………………….

##### ( Page – 222 )

Question 3

The cross ………………the wire ?

Question 4

90 C ……………………the wire .

Question 5

Estimate ………………………numbers …………

Question 6

Calculate …………….. cross section ……………..

Question 7

A 3.0 m …………………………..copper is …………..

Question 8

Find out …………………….applied on it .

Question 9

A very …………………..conductance ?

Question 10

What length ………………………10 ohms ?

Question 11

The specific …………………cross section .

Question 12

A piece ………………………respectively .

Question 13

A thick ……………………………resistance .

Question 14

A wire …………..new wire .

Question 15

A 1 kg ……………these wires .

Question 16

Two coppers …………………….wire B .

Question 17

Two wires ………………respectively .

Question 18

A 200 V ………………………..filament .

Question 19

A rectangular ……………………………..temperature ………

Question 20

Two wires ………………………materials ?

Question 21

A 100 …………………….the Bulb .

Question 22

The maximum ………………….maximum current .

Question 23

How much ………………………..minute ?

Question 24

Compute  the …………………….20 ohms ..

Question 25

A heating …………… the element .

Question 26

An electric ……………….the motors .

Question 27

An electric  ……………………….the press .

Question 28

A current …………….. wire ?

Question 29

A bulb ………………filament ?

Question 30

Find the …………………… supply line .

##### ( Page – 223 )

Question 31

Find the ……………..filament .

Question 32

Find the ……………..filament .

Question 33

A lamp illumination . find

(i)………………………

(ii)……………………….

(iii)……………………….

Question 34

In a ……………..operating .

(i)………………………

(ii)……………………….

(iii)……………………….

Question 35

We have …………….for it .

Question 36

Two cities …………..the wires .

Question 37

A 500 watt ………………liberated .

Question 38

An electric ………………….its element .

Question 39

Calculate ……………….glowing .

Question 40

Two bulbs ……………the bulbs .

Question 41

Two resistor ………………….resistor R2 .

Question 42

A 60 watts …………….. become 120/(48 +6 ) A .

Question 43

How can …………………….4 ohms .

Question 44

Join three ……………2 ohms .

Question 45

A 5 ohms ……………….find n .

Question 46

Three resistor ………….find .

(a)………………………

(b)……………………….

Question 47

Three resistor ………….find .

(a)………………………

(b)……………………….

(c)…………………

Question 48

A 150 ohms …………………mains .

Question 49

An arc ………………same current .

Question 50

A filament ………………supply .

Question 51

Each of ………………..of them ?

##### ( Page – 224 )

Question 52

Three resistors …………………..A and B .

Question 53

Four resistors ……………………..corners .

Question 54

Calculate …………………resistors .

Question 55

Calculate …………………resistors .

Question 56

Question 57

The resistance …………………of silver ?

Question 58

The resistance ……………………temperature .

Question 59

A heating ……………………….involved is .

Question 60

The resistance ………………….carbon is ……………

Question 61

A metallic …………………..its material .