c
(c) \(P = {V_{r.m.s.}} \times {i_{r.m.s.}} \times \cos \phi \)\( = \frac{{100}}{{\sqrt 2 }} \times \frac{{100 \times {{10}^{ - 3}}}}{{\sqrt 2 }} \times \cos \frac{\pi }{3}\)\( = \frac{{{{10}^4} \times {{10}^{ - 3}}}}{2} \times \frac{1}{2} = \frac{{10}}{4} = 2.5\;watt\)