Question

In a.c.circuit,the current and voltage are given by i=5coswt and V=2oosinwt.power loss in the circuit is

Answer 1

A/C to question,
i = 5cosωt
i = 5sin(ωt + π/2) [ we know , sin(90+A) = cosA ]

V = 200sinωt
V = 200sin(ωt + 0)

hence, phase difference between I and V is
Φ = π/2 - 0 = π/2

now, Power loss in circuit = Vi.cosΦ
where V and I are sinusoids rms values, Φ is the phase difference between Voltage and current.
because Φ = π/2 => cosΦ = 0
so, Power loss in circuit = 0