Question

An electric bulb rated 200 V - 100 W is connected to a 160 V power supply. The power consumed by it would be:

• A. 64 W
• B. 80 W
• C. 100 W
• D. 125 W

Answer 1

The Correct Option is A

The power consumed by a device is related to the voltage applied and the resistance of the device.

The formula for power is:

\(P=\frac{V^2}{R}\)​.

The resistance R of the bulb can be found using the rated voltage and power of the bulb, which are 200 V and 100 W, respectively.

We use the formula

\(R = \frac{V_{\text{rated}}^2}{P_{\text{rated}}} = \frac{200^2}{100} = 400 \, \Omega\)

Now, we calculate the power consumed when the voltage applied is 160 V using the same formula:

\(P = \frac{160^2}{400} = \frac{25600}{400} = 64 \, W\)

Thus, the power consumed by the bulb when connected to a 160 V power supply is 64 W.

Answer 2

Given bulb ratings: 200 V, 100 W

First, calculate the resistance of the bulb:

P = V²/R ⇒ R = V²/P

R = (200)²/100 = 400 Ω

When connected to 160 V supply:

P_actual = V_supply²/R

P_actual = (160)²/400 = 25600/400 = 64 W

The power consumed would be 64 W.