Question

Solve the following problem.

A battery of emf 12 V and internal resistance 3 Ω is connected to a resistor. If the current in the circuit is 0.5 A,

1. Calculate resistance of resistor.
2. Calculate terminal voltage of the battery when the circuit is closed.

Answer 1

Given: E = 12 V, r = 3 Ω, I = 0.5 A

To find: a. Resistance (R)
b. Terminal voltage (V)

Formulae: i. E = I (r + R)
ii. V = IR

Calculation: From formula (i),

E = Ir + IR

∴ R = `("E"-"Ir")/"I"`

= `(12-0.5xx3)/0.5`

= 21 Ω

From formula (ii),

V = 0.5 × 21

= 10.5 V

1. The resistance of a resistor is 21 Ω.
2. The terminal voltage of the battery when the circuit is closed is 10.5 V.