NCERT Class 12 Physics Solutions Current Electricity- NCERT Solutions prepared for CBSE students by the best teachers in Delhi.

Class XII Chapter 3 –Current Electricity Physics

Question 3.1: The storage battery of a car has an emf of 12 V. If the internal resistance of the battery is 0.4, what is the maximum current that can be drawn from the battery?

Answer: Emf of the battery, E = 12 V

Internal resistance of the battery, r = 0.4

Maximum current drawn from the battery = I

According to Ohm’s law,

The maximum current drawn from the given battery is 30 A.

Question 3.2: A battery of emf 10 V and internal resistance 3 is connected to a resistor. If the current in the circuit is 0.5 A, what is the resistance of the resistor? What is the terminal voltage of the battery when the circuit is closed?

Answer Emf of the battery, E = 10 V

Internal resistance of the battery, r = 3

Current in the circuit, I = 0.5 A

Resistance of the resistor = R

The relation for current using Ohm’s law is,

Terminal voltage of the resistor = V

Question 3.3: (a) Three resistors 1 , 2 , and 3 are combined in series. What is the total resistance of the combination?

(b) If the combination is connected to a battery of emf 12 V and negligible internal resistance, obtain the potential drop across each resistor.

Answer: (a) Three resistors of resistances 1 , 2 , and 3 are combined in series. Total resistance of the combination is given by the algebraic sum of individual resistances. Total resistance = 1 + 2 + 3 = 6

(b) Current flowing through the circuit = I

Emf of the battery, E = 12 V

Total resistance of the circuit, R = 6

The relation for current using Ohm’s law is,

Potential drop across 1 resistor = V1

From Ohm’s law, the value of V1 can be obtained as

V1 = 2 × 1= 2 V … (i)

Potential drop across 2 resistor = V2

Again, from Ohm’s law, the value of V2 can be obtained as

V2 = 2 × 2= 4 V … (ii)

Potential drop across 3 resistor = V3

Again, from Ohm’s law, the value of V3 can be obtained as

V3 = 2 × 3= 6 V … (iii)

Therefore, the potential drop across 1 , 2 , and 3 resistors are 2 V, 4 V, and 6 V

respectively.

Question 3.4: (a) Three resistors 2 , 4 and 5 are combined in parallel. What is the total resistance of the combination?

(b) If the combination is connected to a battery of emf 20 V and negligible internal resistance, determine the current through each resistor, and the total current drawn from the battery.

Question 3.5: At room temperature (27.0 °C) the resistance of a heating element is 100 . What is the temperature of the element if the resistance is found to be 117 , given that the temperature coefficient of the material of the resistor is.?

Question 3.6:A negligibly small current is passed through a wire of length 15 m and uniform crosssection 6.0 × 10−7 m2, and its resistance is measured to be 5.0 . What is the resistivity of the material at the temperature of the experiment?

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