Question

The emf of a storage battery of a car is 6.0 V. If internal resistance of the battery is 0.2 $\Omega$, then maximum power drawn from the battery is ____ W.

• A. 2.4
• B. 180
• C. 15
• D. Zero

Hint:

Maximum \textbf{Efficiency} occurs when $R$ is very large, but Maximum \textbf{Power} occurs specifically when $R = r$.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
According to the Maximum Power Transfer Theorem, maximum power is delivered to an external load when the load resistance $R$ is equal to the internal resistance $r$ of the source ($R = r$).
Step 2: Formula Application:
Maximum Power $P_{max} = \frac{E^2}{4r}$.
Step 3: Explanation:
Given $E = 6.0$ V and $r = 0.2$ $\Omega$. $$P_{max} = \frac{(6.0)^2}{4 \times 0.2} = \frac{36}{0.8} = 45 \text{ W}$$
Step 4: Final Answer:
The maximum power is 45 W.