First slide

Electrical power

Question

Three 60 W, 120 V light bulbs are connected across 12o V power line as shown in fig. The total power dissipated in the three bulbs is

Moderate

A

60W
B

180w
C

90 W'
D

40 W

Solution

The resistance of each bulb is given by
$R = \frac{V^{2}}{P} = \frac{(120)^{2}}{60} = 240 Ω$
Total resistance of the circuit
$\begin{array}{l} R = R + \frac{R \times R}{R + R} \\ = 240 + \frac{240 \times 240}{240 + 240} = 360 Ω \end{array}$
The current in the circuit
$i = \frac{V}{R} = \frac{120}{360} = \frac{1}{3} amp$
Total power produced is
$P = i^{2} R = {(\frac{1}{3})}^{2} \times 360 = 40 W$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App