Question

An AC source is rated at $220V,50Hz$. The time taken for voltage to change from its peak value to zero is

• A. $50sec$
• B. $0.02sec$
• C. $5sec$
• D. $5x{10}^{-3}sec$

Answer 1

The correct option is D

$5x{10}^{-3}sec$

Explanation for the correct option:

Total time taken to complete one cycle is $T=\frac{I}{f}$

where $f$ is frequency $=50Hz$

Hence, $T=\frac{1}{50}$

Time taken $t$ by voltage to change from its peak value to zero is $t=\frac{T}{2}-\frac{T}{4}=\frac{T}{4}$

$$\begin{gathered} \Rightarrow t=\frac{1}{4x50Hz} \\ \Rightarrow t=\frac{1}{200} \\ \Rightarrow t=5x{10}^{-3}sec. \end{gathered}$$

Hence, option (d) is correct.