Question

A battery of four cells in series, each having an emf of 1.4 V and an internal resistance of 2 $\Omega$ is to be used to charge a small 2 V accumulator of negligible internal resistance. what is the charging current?

• A. 0.1 A
• B. 0.2 A
• C. 0.3 A
• D. 0.45 A

Answer 1

The correct option is D 0.45 A

If four cell having resistance of $2\Omega$ and voltage $1.4V$ connected in series then

$R_{eq}=4\times 2\Omega =8\Omega$

Total Voltage$=4\times 1.4=5.6V$

As given battery is charging by $2V$ then potential difference across $8\Omega$ is ,

$E=5.6-2=3.6V$

Charging current $=\frac{E}{R_{eq}}=\frac{3.6}{8}=0.45A$

Correct option is D