Question

Three equal resistors connected in series across a source of e.m.f dissipate 10 watts of power. What will be the power dissipated in watts if the same resistors are connected in parallel across the same source of e.m.f?

• A. 10 W
• B. 30 W
• C. 90 W
• D. $\frac{10}{3}W$

Answer 1

The correct option is C 90 W

$R_2=3R,P=10W$
$P=\frac{V^2}{R_{series}}\Rightarrow 10=\frac{V^2}{3R}\Rightarrow \frac{V^2}{R}=30$
$P^{\prime }=\frac{V^2}{R/3}=3\frac{V^2}{R}=3\times 30=90W$