Answered: 1. Alfredo deDarke sleeps with a…

Glencoe Physics: Principles and Problems, Student Edition

1st Edition

ISBN:9780078807213

Author:Paul W. Zitzewitz

Publisher:Paul W. Zitzewitz

Chapter27: Quantum Theory

Section: Chapter Questions

Problem 49A

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Transcribed Image Text:Electrical Power – you still have none. Show work on a separate sheet of paper and use units. 1. Alfredo deDarke sleeps with a 7.5-Watt night light bulb on. He turns it on before getting in bed and turns it off 8.0 hours later. a. Determine the amount of energy used during one evening in units of kiloWatt•hours. b. Electrical energy costs 13 cents/kWh where Alfredo lives. Determine the annual (365 days) cost of this practice of using a 7.5-Watt night light. c. Determine the annual savings if Alfredo replaced his 7.5-Watt incandescent night light by a 0.5-Watt LED night light. 2. Having recently lost her job, Penny Penching is looking for every possible means of cutting costs. She decides that her 4.0-Watt clock radio alarm does not need to be on for 24 hours every day since she only needs it for waking up after her average 8-hour sleep. So she decides to plug it in before going to sleep and to unplug it when waking. Penny pays 12 cents per kiloWatt•hour for her electricity. How much money is Penny able to save over the course of a month (31 days) with her new alarm clock usage pattern? 3. The power of a 1.5-volt alkaline cell varies with the number of hours of operat deliver as much as 13 A through a copper wire connected between terminals. Determine the power of a brand new D- A brand new D-cell can cell. 4. A central air conditioner in a typical American home operates on a 220-V circuit and draws about 15 A of current. a. Determine the power rating of such an air conditioner. b. Determine the energy consumed (in kWh) if operated for 8.0 hours per day. c. Determine the monthly cost (31 days) if the utility company charges 13 cents per kWh. 5. During the Christmas season, Sel Erbate uses the equivalent of 45 strings of 100 mini-bulbs to light the inside and outside of his home. Each 100-bulb string of lights is rated at 40 Watts. The average daily usage of the strings is 7 hours. The lights are used for approximately 40 days during the holiday season. a. Determine the resistance of each string of lights. Each is powered by 110-volt outlet. b. Determine the energy consumed (in kWh) by all of the lights over the course of 40 days. c. If Sel pays 12 cents/kWh for electrical energy, then what is the total cost of Christmas lighting for a single season? 6. The headlights in a car use 95 W of power. A driver parks her car but leaves the lights on. The 12 V battery has 3.4 x 10° C of stored charge. How long does it take for the battery to lose its charge?

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