Question

. A storage battery of emf 8.0 V and internal
resistance 0.5 12 is being charged by a 120 V
d.c. supply using a series resistor of 15.5 12.
What is the terminal voltage of the battery
during charging? What is the purpose of
having a series resistor in the charging
circuit?​

Answer 1

Emf of the storage battery, E = 8.0 V

Internal resistance of the battery, r = 0.5 Ω

DC supply voltage, V = 120 V

Resistance of the resistor, R = 15.5 Ω

Effective voltage in the circuit = V1

R is connected to the storage battery in series. Hence, it can be written as

V1 = V - E

V1 = 120 - 8 = 112 V

Current flowing in the circuit = I, which is given by the relation,

Voltage across resistor R given by the product, IR = 7 × 15.5 = 108.5 V

DC supply voltage = Terminal voltage of battery + Voltage drop across R

Terminal voltage of battery = 120 - 108.5 = 11.5 V

A series resistor in a charging circuit limits the current drawn from the external source. The current will be extremely high in its absence. This is very dangerous