c
(c) \(P = {E_{rms}}{i_{rms}}\cos \phi = \frac{{{E_0}}}{{\sqrt 2 }} \times \frac{{{i_0}}}{{\sqrt 2 }} \times \frac{R}{Z}\)
==> \(\frac{{{E_0}}}{{\sqrt 2 }} \times \frac{{{E_0}}}{{Z\sqrt 2 }} \times \frac{R}{Z}\)\( \Rightarrow \,\,P = \frac{{E_0^2R}}{{2{Z^2}}}\)
Given \({X_L} = R\) so, \(Z = \sqrt 2 R\)\( \Rightarrow \,P = \frac{{E_0^2}}{{4R}}\)