**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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