Question

A new LED light bulb uses 10 watts of power. Since energy = power × time, then the energy used for this light bulb can be found by multiplying the power times the time the bulb is lit. If the bulb is lit for one hour, the energy used will be 10 watt-hours or 10 Wh. If three 10 watt bulbs in one room are kept on for 5 hours, how many watt-hours of energy are used? Parents sometimes yell at their children for leaving the light on in their bedroom when they aren't in the room. If the child's room is lit with two 10 watt bulbs for one extra hour a day for every day of the year (365), and the cost of energy is $0.068 per kilowatt-hour (kWh), how much money is wasted on lighting that isn't being used, to the nearest cent.

          A new LED light bulb uses 10 watts of power.
Since energy = power × time, then the energy used for this light bulb can be found by multiplying the power times the time the bulb is lit. If the bulb is lit for one hour, the energy used will be 10 watt-hours or 10 Wh. If three 10 watt bulbs in one room are kept on for 5 hours, how many watt-hours of energy are used?
Parents sometimes yell at their children for leaving the light on in their bedroom when they aren't in the room. If the child's room is lit with two 10 watt bulbs for one extra hour a day for every day of the year (365), and the cost of energy is $0.068 per kilowatt-hour (kWh), how much money is wasted on lighting that isn't being used, to the nearest cent.

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Added by David J.

Elementary and Intermediate Algebra

Alan S. Tussy, R. David Gustafson 5th Edition

Instant Answer

Solved by Expert Nathan Smith

05/31/2022

Step 1

- Each bulb uses 10 watts of power. - There are 3 bulbs, so the total power is \(3 \times 10 = 30\) watts. - The bulbs are on for 5 hours, so the energy used is \(30 \, \text{watts} \times 5 \, \text{hours} = 150 \, \text{watt-hours (Wh)}\). Show more…

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A new LED light bulb uses 10 watts of power. Since energy = power × time, then the energy used for this light bulb can be found by multiplying the power times the time the bulb is lit. If the bulb is lit for one hour, the energy used will be 10 watt-hours or 10 Wh. If three 10 watt bulbs in one room are kept on for 5 hours, how many watt-hours of energy are used? Parents sometimes yell at their children for leaving the light on in their bedroom when they aren't in the room. If the child's room is lit with two 10 watt bulbs for one extra hour a day for every day of the year (365), and the cost of energy is $0.068 per kilowatt-hour (kWh), how much money is wasted on lighting that isn't being used, to the nearest cent.

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00:01 In order to find how many watt hours of energy are used for three bulbs kept on for five hours, we're going to use the formula power times time equals energy.

00:14 So for one bulb at five hours, we would just need to multiply the 10 watt hours of energy times the five hours that it's on, which would give us 50 watt hours.

00:41 Now that's just for one bulb, and it asks for three.

00:45 So for three bulbs, we would need to multiply that 50 watt hours that one bulb does at five hours times three.

00:55 So three times 50 is equal to 150 watt hours.

01:03 Now that is the first part of the question.

01:06 The second part asks how much money is wasted if two bulbs are kept on one extra hour per day every day of the year if the cost cost of energy is 0 .068 cents per kilowatt hour.

01:18 Well, we're first going to need to find how much energy is done, is expelled over that year for those two bulbs.

01:29 So for two bulbs in one day, if they're on for an extra hour, that would be two times the 10 watt hours that it is for one bulb, which would be 20 watt hours.

01:47 And that's just for one day.

01:49 So for the whole year, that would be 365 days.

01:56 So we would need to do 365 times the 20 watt hours.

02:01 Watt hours, which gives us 7 ,300 watt hours.

02:11 So that's how much energy is used in a whole year...

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