Question

The storage battery of a car has an emf of $12\text{V}$. If the internal resistance of the battery is $0.4\Omega$, what is the maximum current that can be drawn from the battery ?

• A. $10\text{A}$
• B. $20\text{A}$
• C. $30\text{A}$
• D. $40\text{A}$

Answer 1

The correct option is C $30\text{A}$

Given:
EMF, $E=12\text{V}$;
Internal resistance, $r=0.4\Omega$

The maximum current is drawn from the battery when the external resistance in the circuit is zero, i.e., $R=0$.

Thus, $I_{max}=\frac{E}{r}=\frac{12}{0.4}=30\text{A}$

So, option $\left(c\right)$ is right.

Why is question ? The maximum current is drawn from the battery when the external resistance in the circuit is zero.