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Back to Exercise: Electric Power

Exercises: Electric Power

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Grade 11·22 problems·~30 min·OpenStax Physics (High School)·section·sec-19-4
Work through problems with immediate feedback
A

Recall / Warm-Up

1.

In mechanics, power is defined as the rate of doing work. Which expression correctly states this definition?

2.

A circuit element has a potential difference of VV across it and a current II flowing through it. Which expression gives the power delivered to the element?

3.

Ohm's Law states the relationship between voltage, current, and resistance in a resistor. Which equation is correct?

B

Fluency Practice

1.

A hair dryer operates at 120 V120\ \text{V} and draws a current of 12.5 A12.5\ \text{A}. Calculate the power consumed by the hair dryer in watts.

2.

A 60 W60\ \text{W} light bulb operates at 120 V120\ \text{V}. What current flows through the bulb? Give your answer in amperes.

3.

A resistor has resistance R=40 ΩR = 40\ \Omega and carries a current of 3 A3\ \text{A}. Calculate the power dissipated in the resistor using the formula P=I2RP = I^2R.

Decision tree showing which power formula to use: P=IV when given I and V, P=I-squared-R when given I and R, P=V-squared-over-R when given V and R, with the V and R row highlighted
4.

A resistor has V=24 VV = 24\ \text{V} across it and R=8 ΩR = 8\ \Omega. Which formula should you use to calculate power directly from these two values, and what is the result?

5.

An electric heater has resistance R=20 ΩR = 20\ \Omega and is connected to a 240 V240\ \text{V} outlet. Calculate the power dissipated using P=V2/RP = V^2/R.

6.

A 150 W150\ \text{W} refrigerator runs for 8 hours8\ \text{hours}. How many kilowatt-hours of energy does it use?

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