Question

The instantaneous values of current and potential difference in an alternating circuit are $E = 100 \cos \omega t$ respectively. r.m.s. value of wattless current (in amp) in the circuit is

• A. 1
• B. $1 / \sqrt { 2 }$
• C. 100
• D. Zero

Answer 1

Answer: (B)

$1 / \sqrt { 2 }$

Answer 2

r.m.s. value of wattless current $= \frac { i _ { 0 } } { \sqrt { 2 } } \sin \phi$ In this question i₀ = 1 A and $\phi = \frac { \pi } { 2 }$ . So r.m.s. value of wattless current $= \frac { 1 } { \sqrt { 2 } } A$