Question

The magnetic field energy in an inductor changes from maximum value to minimum value in 5.0 ms when connected to an AC source,. The frequency of the source is

• A. 20 Hz
• B. 50 Hz
• C. 200 Hz
• D. 500 Hz

Answer 1

The correct option is B 50 Hz

$\frac{T}{4}=5\times {10}^{-3}sec$
$T=20\times {10}^{-3}sec$
$F=\frac{1}{T}=\frac{1}{20\times {10}^{-3}}=\frac{1000}{20}$
f = 50 Hz