Question

RMS current in a circuit of 50 Hz frequency is 5 A. Value of current $\frac{1}{300}$ seconds after its peak value is

• A. $5\sqrt{2}$ A
• B. $\frac{5}{\sqrt{2}}$ A
• C. $5\sqrt{\frac{3}{2}}$ A
• D. 2.5 A

Answer 1

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

$i_o=i_{rms}\sqrt{2}=5\sqrt{2}Ai=i_o\cos wt$ $\Rightarrow i=5\sqrt{2}\cos \frac{2\pi \times 50}{300}=5\sqrt{2}\cos \frac{\pi }{3}=5\sqrt{2}\times \frac{1}{2}=\frac{5}{\sqrt{2}}A$