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 . — End of Electric Resistance and Ohm’s Law Numericals :–

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