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

Explanation

`P_1 = 10 W`
In series combination , total resistance = 3R
Power = `P_1 = (V^2)/(3R)`

In paralle combination , total resistance = R/3
`R_2 =(V^2)/(R//3)`
`implies (P_1)/(P_2) =(R//3)/(3R) implies (10)/(P_2) =(R//3)/(3R)`
`(10)/(P_2) =(R)/(3xx3R) =1/9 implies P_2 `= 90 watts