The magnetic energy in an inductor changes from maximum value to minimum value in 5 ms . When connected to…
The magnetic energy in an inductor changes from maximum value to minimum value in 5 ms . When connected to an a.c. source, the frequency of the source is
50 Hz
200 Hz
500 Hz
20 Hz
Solution
Magnetic field energy changes from maximum to minimum in $\frac{1}{4}^{\text {th }}$ time of a cycle
$\begin{aligned}
& \therefore \quad \frac{\mathrm{T}}{4}=5 \mathrm{~ms} \Rightarrow \mathrm{~T}=20 \mathrm{~ms} \\
& \therefore \quad \mathrm{f}=\frac{1}{\mathrm{~T}}=\frac{1}{20 \times 10^{-3}}=50 \mathrm{~Hz}
\end{aligned}$
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