Question

Two equal resistance when connected in series to a battery, consume electric power of $60\, W$. If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be :

• A. 60 W
• B. 240 W
• C. 30 W
• D. 120 W

Answer 1

Answer: (B)

240 W

Answer 2

In series condition, equivalent resistance is 2R thus power consumed is 60W $= \frac{ \varepsilon^2}{2R}$ In parallel condition, equivalent resistance is R/2 thus new power is $P' = \frac{\varepsilon^2}{(R / 2)}$ or $P' = 4\, P = 240\, W$