Question

Two electric bulbs rated $P_1,W,V$ volt, and $P_2$, $W$, $V$ volt are connected in series, across V-volt supply. The total power consumed is

• A. $\frac{P_1+P_2}{2}$
• B. $\sqrt{P_1.P_2}$
• C. $\frac{P_1.P_2}{P_1+P_2}$
• D. $P_1+P_2$

Answer 1

The correct option is C $\frac{P_1.P_2}{P_1+P_2}$

When connected in series.

Total power $=\frac{V^2}{R_1+R_2}$

$=\frac{V^2}{\frac{V^2}{P_1}+\frac{V^2}{P_2}}$

$=\frac{P_1{P}_2}{P_1+P_2}$