Physics Class 12 NCERT Solutions: Chapter 3 Current Electricity Part 1

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Batteries have internal resistance

Batteries Have Internal Resistance

Batteries have internal resistance

Q: 1. The storage battery of a car has an emf of . If the internal resistance of the battery is , what is the maximum current can be drawn from the battery?

Answer:

Internal resistance of the battery,

Maximum current drawn from the battery

According to Ohm’s law,

The maximum current drawn from the given battery is

Q: 2. A battery of emf and internal resistance is connected to a resistor. If the current in the circuit is , 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,

Internal resistance of the battery,

Current in the circuit,

Resistance of the resistor

The relation for current using Ohm’s law is,

Terminal voltage of the resistor

According to Ohm’s law,

Therefore, the resistance of the resistor is and the terminal voltage is .

Q: 3. (A) Three resistors are combined in series. What is the total resistance of the combination?

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

Answer:

(A) Three resistors of resistances are combined in series. What is the total resistance of the combination is given by the algebraic sum of individual resistances. Total resistance

(B) Current flowing through the circuit

Emf of the battery,

Total resistance of the circuit,

The relation for current using Ohm’s law is,

Potential drop across resistor

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

Potential drop across resistor

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

Potential drop across resistor

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

Therefore, the potential drop across resistors are respectively.