Question

If the equations of alternating voltage and alternating current in an A.C. circuit are $E=E_0\sin \omega t$ volt and $I=I_0\sin (\omega t-\pi /2)$ ampere respectively. The power loss in the circuit will be

• A. zero
• B. $\frac{E_0{I}_0}{\sqrt{2}}$
• C. $\frac{E_0{I}_0}{2}$
• D. $\frac{EI}{\sqrt{2}}$

Answer 1

Answer: (A)

zero

Since power in ac circuits is given by

$P=V_{rms}{I}_{rms}\cos \varphi$

here $\varphi =\pi /2$

Therefore

$P=V_{rms}{I}_{rms}\cos \pi /2=0$