The electrical energy spent in kilowatt-hours and Joules is to be determined. Concept Introduction: If the cost of one unit of energy and the monthly cost are known, then the energy spent per month can be calculated by dividing the monthly cost by the cost of one unit of energy.

Question

Most people find waterbeds uncomfortable unless the water temperature is maintained at about 85 °F. Unless it is heated, a waterbed that contains 892 L of water cools from 85 °F to 72 °F in 24 hours. Estimate the amount of electrical energy required over 24 hours, in kWh, to keep the bed from cooling. Note that 1 kilowatt-hour (kWh) = 3.6 × 106 J, and assume that the density of water is 1.0 g/mL (independent of temperature). What otherassumptions did you make? How did they affect your calculated result (i.e., were they likely to yield “positive” or “negative” errors)?

Answer 1

Question

Chapter 10, Problem 24E

Interpretation Introduction

Interpretation:

The electrical energy spent in kilowatt-hours and Joules is to be determined.

Concept Introduction:

If the cost of one unit of energy and the monthly cost are known, then the energy spent per month can be calculated by dividing the monthly cost by the cost of one unit of energy.

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Most people find waterbeds uncomfortable unless the water temperature is maintained at about 85 °F. Unless it is heated, a waterbed that contains 892 L of water cools from 85 °F to 72 °F in 24 hours. Estimate the amount of electrical energy required over 24 hours, in kWh, to keep the bed from cooling. Note that 1 kilowatt-hour (kWh) = 3.6 × 106 J, and assume that the density of water is 1.0 g/mL (independent of temperature). What otherassumptions did you make? How did they affect your calculated result (i.e., were they likely to yield “positive” or “negative” errors)?

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