Power: watts and energy per second

Question 1

Which statement below correctly defines power and identifies its SI unit?

Accepted Answer

Power is the rate at which energy is transferred or converted, and its SI unit is the watt (W), which equals one joule per second.

Answer

Power is the total amount of energy used, and its SI unit is the joule (J).

Answer

Power is the amount of energy transferred each minute, and its SI unit is the watt (W).

Answer

Power is the force applied to an object, and its SI unit is the newton (N).

Question 2

Which of the following statements gives the correct definition of power and its SI unit?

Accepted Answer

Power is the rate at which energy is transferred (energy ÷ time); its unit is the watt (W).

Answer

Power is the amount of energy stored in a system; its unit is the joule (J).

Answer

Power is the speed at which work is done; its unit is the newton (N).

Answer

Power is the rate of energy transfer; its unit is watts per second (W/s).

Question 3

An electric kettle has a power rating of 1500 W and it transfers 4500 J of energy to heat water. How many seconds does the kettle run, and how much energy does a 75 W desk lamp use if it is left on for the same amount of time?

Accepted Answer

3 seconds; 225 J

Answer

3 seconds; 2,250 J

Answer

0.33 seconds; 25 J

Answer

30 seconds; 225 J

Try three questions

Which statement below correctly defines power and identifies its SI unit?

Which of the following statements gives the correct definition of power and its SI unit?

An electric kettle has a power rating of 1500 W and it transfers 4500 J of energy to heat water. How many seconds does the kettle run, and how much energy does a 75 W desk lamp use if it is left on for the same amount of time?

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