CBSE Class 12 · 2005 · All India · Alternating CurrentVery Short Answer

What is the power dissipated in an a.c. circuit in which the voltage and current are given by

V = 230 sin (ω t + \frac{π}{2})

and

I = 10 sin ω t

Answer: $P = 0$ (zero).

Solution

The current and voltage differ in phase by

ϕ = \frac{π}{2}

P_{a v} = V_{r m s} I_{r m s} cos ϕ = V_{r m s} I_{r m s} cos \frac{π}{2}

Since

cos \frac{π}{2} = 0

, no power is dissipated — this is a wattless circuit.

P_{a v} = 0

CBSE Class 12 Board · 2005 · All India · Subjective