Question

Two electric bulbs related $P_1$ watt V volt and $P_2$ watt V, these are joined in parallel and voltage V are applied to it. The total power will be:-

• A. $P_1+P_2$ watt
• B. $\sqrt{P_1{P}_2}$ watt
• C. $\frac{P_1{P}_2}{P_1+P_2}$
• D. $\frac{P_1+P_2}{P_1{P}_2}$

Answer 1

The correct option is A $P_1+P_2$ watt

Here, $R_1=\frac{V^2}{P_1}$ and $R_2=\frac{V^2}{P_2}$
When they in parallel, the net resistance, $R=\frac{R_1{R}_2}{R_1+R_2}=\frac{V^2}{P_1+P_2}$
Thus, total power, $P=\frac{V^2}{R}=\frac{V^2}{V^2/(P_1+P_2)}=P_1+P_2$ W