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Question: Answered & Verified by Expert
A battery is charged at a potential of 15 $\mathrm{V}$ for 8 hours when the current flowing is $10 \mathrm{~A}$. The battery on discharge supplies a current of $5 \mathrm{~A}$ for 15 hours. The mean terminal voltage during discharge is $14 \mathrm{~V}$. The "Watt-hour" efficiency of the battery is:
PhysicsCurrent ElectricityJEE Main
Options:
  • A $82.5 \%$
  • B $80 \%$
  • C $90 \%$
  • D $87.5 \%$
Solution:
2685 Upvotes Verified Answer
The correct answer is: $87.5 \%$
When the battery is charged then Watt hour $=V I t=15 \times 10 \times 8=1200$ W/hr.

During discharge the watt hour $u=$ $1050 \mathrm{~W} / \mathrm{hr}$.
$$
\begin{gathered}
\therefore \text { Efficiency of battery }=\frac{1050}{1200} \times 100 \\
=87.5 \%
\end{gathered}
$$

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