Question

If the rms current in a $50Hz$ ac circuit is $5A$, the value of the current $1/300$ seconds after its value becomes zero is

• A. $5\sqrt{2}A$
• B. $5\sqrt{\frac{3}{2}}A$
• C. $\frac{5}{6}A$
• D. $\frac{5}{\sqrt{2}}A$

Answer 1

The correct option is B $5\sqrt{\frac{3}{2}}A$

The expression of sinusoidal current is $I=I_p\sin \omega t$

$I=(I_{rms}\times \sqrt{2})\sin (2\pi \times 50\times 1/300)$

$=5\sqrt{2}\sin \pi /3=5\sqrt{2}\times \frac{\sqrt{3}}{2}$

$=5\sqrt{\frac{3}{2}}A$