A light bulb,sold as long-lasting,is rated 95 W at 145 V.The "increased" lifetime comes from using it at 110 V.Assuming negligible change in resistance at the different voltage,what is its power consumption at 110 V?

Question

Quizplus · Accepted Answer

The power consumption at a lower voltage can be calculated using the formula $P = \frac{V^2}{R}$, where $P$ is power, $V$ is voltage, and $R$ is resistance. Since resistance ($R$) remains constant, we can set up a ratio of the power consumptions at the two voltages: $\frac{P_1}{P_2} = \frac{V_1^2}{V_2^2}$. Given $P_1 = 95W$ and $V_1 = 145V$, and $V_2 = 110V$, solving for $P_2$ gives $P_2 = 95W \times (\frac{110V}{145V})^2 \approx 55W$.

A Light Bulb,sold as Long-Lasting,is Rated 95 W at 145