Question

$24$ identical bulbs are connected in series with a supply voltage of $220\text{V}$. These $48\text{W}$ bulbs are designed to operate at $220\text{V}$. Find the power consumed by all the bulbs in the circuit.

• A. $48\text{W}$
• B. $2\text{W}$
• C. $24\text{W}$
• D. $4\text{W}$

Answer 1

The correct option is B $2\text{W}$

Since voltage rating of the bulb and supply voltage is same and all the bulbs are connected in series,

We can use,

$\frac{1}{P_{eq}}=\frac{1}{P_1}+\frac{1}{P_2}+....\frac{1}{P_n}$

Here $P_1=P_2=P_3=.....48\text{W}$

$\frac{1}{P_{eq}}=\frac{1}{48}+\frac{1}{48}$....upto 24 times

$\Rightarrow \frac{1}{P_{eq}}=\frac{24}{48}$

$\therefore P_{eq}=2\text{W}$