A sinusoidal  current flows through a resistor of resistance R. If the peak current is I_p, then the power dissipated is

• A

  ${\mathrm{I}}_{\mathrm{p}}^2\mathrm{R} \cos \mathrm{\theta }$

• B

  $\frac{1}{2} {\mathrm{I}}_{\mathrm{p}}^2 \mathrm{R}$

• C

  $\frac{4}{\mathrm{\pi }} {\mathrm{I}}_{\mathrm{p}}^{2 }\mathrm{R}$

• D

  $\frac{1}{\mathrm{\pi }} {\mathrm{I}}_{\mathrm{p}}^{2 }\mathrm{R}$