Question

Two electric bulbs rated $P_{1}$ watt V volts and $P_{2}$ watt V volts are connected in parallel and V volts are applied to it. The total power will be

• A. $P_{1} + P_{2}watt$
• B. $\sqrt{P_{1}P_{2}}$watt
• C. $\frac{P_{1}P_{2}}{P_{1} + P_{2}}watt$
• D. $\frac{P_{1} + P_{2}}{P_{1}P_{2}}watt$

Answer 1

Answer: (A)

$P_{1} + P_{2}watt$

Answer 2

If resistances of bulbs are $R_{1}$ and $R_{2}$ respectively then in parallel $\frac{1}{R_{P}} = \frac{1}{R_{1}} + \frac{1}{R_{2}}$⇒ $\frac{1}{\left( \frac{V^{2}}{P_{p}} \right)} = \frac{1}{\left( \frac{V^{2}}{P_{1}} \right)} + \frac{1}{\left( \frac{V^{2}}{P_{2}} \right)}$

⇒ $P_{P} = P_{1} + P_{2}$