Apparent Power

Q. The magnetic field energy in an inductor changes from maximum value to minimum value in 5 ms when connected to an AC source. The frequency of the source is

1. $20\text{Hz}$
2. $50\text{Hz}$
3. $20\text{Hz}$
4. $500\text{Hz}$

Q. The magnetic field energy in an inductor changes from maximum value to minimum value in 5 ms when connected to an AC source. The frequency of the source is

1. $20\text{Hz}$
2. $50\text{Hz}$
3. $20\text{Hz}$
4. $500\text{Hz}$