Question

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

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

Answer 1

Answer: (B)

$240W$

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