Question

Three $60 \,W , 120 \,V$ light bulbs are connected across a $120 \,V$ power source. If resistance of each bulb does not change with current, then find out total power delivered to the three bulbs.

• A. 180 W
• B. 20 W
• C. 40 W
• D. 60 W

Answer 1

Answer: (C)

Here $R=\frac{V^{2}}{P}$,
Total power supplied
$=\frac{V^{2}}{3 / 2 R}=\left(\frac{2}{3}\right)\left(\frac{V^{2}}{R}\right)$
$=\frac{2}{3} \times 60=40\,W$