Three equal resistors connected in series across a source of e.m.f. together dissipate 10 watts of p

Question

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

Professor PC Thomas Classes · Answer

Power in series $P_s = V^2 / 3R = 10 \mathrm{~W}$. In parallel $P_p = V^2 / (R/3) = 9 P_s = 90 \mathrm{~W}$.