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.

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

Tardigrade Admin · Accepted Answer

<img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/physics/d582071007760013fcd53ecebd46b3de-.png" /> Here R=(V2/P), Total power supplied =(V2/3 / 2 R)=((2/3))((V2/R)) =(2/3) × 60=40 W

Q. 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.

180 W

20 W

40 W

60 W

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

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