Problem

The battery for a certain cell phone is rated at …

02:18

Problem 40 Hard Difficulty

Electric space heater. A "540 W" electric heater is designed to operate from 120 V lines. (a) What is its resistance, and (b) what current does it draw? (c) At 7.4$\notin$ per kWh, how much does it cost to operate this heater for an hour? (d) If the line voltage drops to $110 \mathrm{V},$ what power does the heater take, in watts? (Assume that the resistance is constant, although it actually will change because of the change in temperature.)

Answer

$$454 \mathrm{W}$$

Related Courses

Physics 102 Electricity and Magnetism

College Physics

Chapter 19

Current, Resistance, and Direct-Current Circuit

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Video Transcript

we're given the heater has a power eating off 440. What on? It works at old age off 120 words Now for body. We want to find out the distance off the heater. We know that power is re square by our, which uses our is We're square by P that is 1 20 squared divided by 5 40 which turns out to be 26.7 omega 26 points on home. If I'd be We want to find out the current We know that power is voltage Time's current which gives us current is he baby which is powered by voltage which is 5 40 divided by 1 20 which turns out to be 4.5 appear now for Patsy were given that the cost off electricity is 6.4 cents per kilowatt Har No, If we run the machine for one heart, that would be the amount of energy would be power times The time the party is 544 on the time is one heart which is 60 minutes which is 60 times 60 seconds. And we know that what I'm second is Jordan. But We simply want to find out Kilowatt Harr's So we simply do 540 watts, but played by one heart. This would give us 540 Ward Harr's note and that we need to use hard here as unit instead ofthe segments. I started out with seconds because that is what we would usually thing to do because I study assignment it. In this case, we need to use heart now 5 40 What highs? Our cedar. 0.540 into. Thank you, Waterhouse. And thank you. Waters is gonna kill our water. And hence you get 0.5 for serial killer. What cars? Now that you know this, that cost is because for unit ability, which is 7.4 cent, you know what hard modified by the energy itself, which is sitting on 54 Serial killer. What are notice how the similar units cattle off and we're left with sense. This is because we expect you get the answer. In terms of money. This turns out to be 3.9 cents now for part B. You want to find out what would happen if we ran this instead of 110 words. What would power? Well, if you know this, we know power is simply we square by our we square is 410 square. You run it by the real resistance is, as we found out, 26.7 own We get it 45.3. What now? What is that disease? 110 by 1 20 square times that off the original power which is 540 once. I'm sorry. This is not for you. 45.3. This is 453 parts.

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