3.2 A battery of emf 10 V and internal resistance 3 Ω 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?
Emf of the battery, E = 10 V
The internal resistance of the battery, r = 3
Current in the circuit, I = 0.5 A
Let R be the resistance of the resistor.
Therefore, according to Ohm's law:
E = IR' = I(R + r)
10 = 0.5(R + 3)
R = 20 - 3 = 17
V = IR (Across the resistor)
= 0.5 x 17 = 8.5 V
Hence, terminal voltage across the resistor = 8.5 V