Three equal resistors connected across a source of e.m.f. together dissipate 10 watt 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 ?
In series, Equivalent resistance = 3R
Power=V23R⇒10=V23R⇒V2=30R
In parallel, 1R′=1R+1R+1R=3R
∴ Equivalent resistance R′=R3
∴ Power =V2R′=30RR/3=90W