Important Questions for Class 12 Chapter 3 - Current Electricity

Important questions based on NCERT syllabus for Chapter 3 - Current Electricity:

Question-1: A battery has an emf of 10 V and internal resistance is observed to be 3 Ω and is connected to a resistor. If the current flowing in the circuit is 0.5 A, calculate the resistance of the resistor? Also, calculate the terminal voltage of the battery when the circuit is closed.

Solution: Given Data :
Given that Emf of the battery, E = 10 V
Battery has an Internal resistance of R = 3 Ω
Current flowing in the circuit, I = 0.5 A
Let the Resistance of the resistor be = R
The relation for current using Ohm’s law is,
Terminal voltage of the resistor = V
According to Ohm’s law,
V = IR
V = 0.5 × 17
V = 8.5 V
Therefore, the resistance of the resistor calculated is 17 Ω and the terminal voltage is found to be
8.5 V.

Question-2: The car has a storage battery with an emf of 12 V. 0.4Ω is the internal resistance of the battery, what is the maximum current that can be drawn from the battery?

Given that Emf of the battery, E = 12 V
Battery has an Internal resistance of R = 0.4 Ω
The Maximum current drawn from the battery is given by = I
According to Ohm’s law,
E = IR
I=12/0.4 = 30 A
The maximum current drawn from the given battery is 30 A.

Question-3: The length of a wire is 15 m and uniform cross – section is 6.0 x 10 – 7 m 2. Negligibly small current is passed through it with a resistance of 5.0 Ω. Calculate the resistivity of the material at the temperature at which the experiment is conducted.

Given that the length of the wire , L = 15 m
Area of cross – section is given as , a = 6.0 x 10 – 7 m^2
Let the resistance of the material of the wire be , R , ie. , R = 5.0 Ω
Resistivity of the material is given as ρ
Therefore, the resistivity of the material is calculated to be 2×10^–7