1) What is the inductance for an inductor with a reactance of 20 ? at a frequenc

Question

1) What is the inductance for an inductor with a reactance of 20 ? at a frequency of 60 Hz?

27 mH

2) A bulb is designed for 100 W at 130 V rms. What is the power dissipated by this bulb if it is used in a 120 V rms circuit?

85.2 W

it will blow out

3) Two 100-W bulbs differ in that one is designed for the American 120 V rms and the other is designed for the European 220 V rms. Which bulb has the greater resistance, and what is that resistance?

12 H 19 H 3.0 H 53 mH

27 mH

2) A bulb is designed for 100 W at 130 V rms. What is the power dissipated by this bulb if it is used in a 120 V rms circuit?

169 W 130 W 100 W

85.2 W

it will blow out

3) Two 100-W bulbs differ in that one is designed for the American 120 V rms and the other is designed for the European 220 V rms. Which bulb has the greater resistance, and what is that resistance?

American, 288 ? ohm American, 144 ? ohm European, 484 ? ohm European, 242 ? ohm they are the same, 265 ? ohm

Explanation / Answer

Part 1-

XL = 2 f L

20 = 2 * 3.14 * 60 * L

L = 0.053 H = 53 mH.

Part 2-

P = [V]2 / R

R = 130 * 130 / 100 = 169 ohms.

This resistance would remain same for the bulb.

So case 2-

P’ = [V’2] / R = 120 * 120 / 169 = 85.2 W.

Part 3-

Again using the same formula- P = [V]2 / R

American – 100 = 120 * 120 / Ramerican

Ramerican = 144 ohms

European- 100 = 220 * 220 / Reuropean

Reuropean = 484 ohms.

European greater resistance.

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