A battery is charged at a potential of 15 $\mathrm{V}$ for 8 hours when the current flowing is $10…
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:
$82.5 \%$
$80 \%$
$90 \%$
$87.5 \%$
Solution
When the battery is charged then Watt hour $=V I t=15 \times 10 \times 8=1200$ W/hr.
During discharge the watt hour $u=$ $1050 \mathrm{~W} / \mathrm{hr}$.
$\begin{gathered}
\therefore \text { Efficiency of battery }=\frac{1050}{1200} \times 100 \\
=87.5 \%
\end{gathered}$