Question

Two equal resistances when connected in series to a battery, consume electric power of $100\text{W}$. If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be

• A. $400\text{W}$
• B. $360\text{W}$
• C. $240\text{W}$
• D. $200\text{W}$

Answer 1

The correct option is A $400\text{W}$

In series connection with battery,

Power, $P=\frac{E^2}{2R}$

Substituting the data given in the question,

$100=\frac{E^2}{2R}.......\left(1\right)$

In parallel combination with battery,

Power , $P^{\prime }=\frac{E^2}{(\frac{R}{2})}=\frac{2E^2}{R}$

Substituting $(1$ in the above equation we get,

$P^{\prime }=2\times 200=400\text{W}$

Hence, option (a) is the correct answer.