Question

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

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

Answer 1

Answer: (B)

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

Answer 2

: Here, $I_{rms} = 5A,\upsilon = 50Hz,t = \frac{1}{300}s$

$I_{0} = \sqrt{2}I_{rms} = 5\sqrt{2}A,$

From $I = I_{0}\sin\omega t = I_{0}\sin 2\pi\upsilon t$

$I = 5\sqrt{2}\sin\left( 2\pi \times 50 \times \frac{1}{300} \right)$

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