1.2 Energy – How Do Machines Work?

Multiple Choice

What is the formula for power?

• $$power=\frac{energy}{time}$$

• $$power=\frac{time}{energy}$$

• $$power=energy\times time$$

• $$power=energy+time$$

Multiple Choice

Which of the situations can increase power?

• more energy is converted and/or transferred in the same amount of time taken

• the same amount of energy is converted and/or transferred in a shorter amount of time

• more energy is converted and/or transferred in a shorter amount of time

• all of the above

Multiple Choice

What is the unit for power?

• joules, j

• joules, J

• watt, w

• watt, W

Multiple Choice

A microwave oven uses 24 000 J of electrical energy every 30 seconds. What is the power of the microwave oven?

• 240 W

• 800 W

• 12 000 W

• 24 000 W

Multiple Choice

A television uses 6 750 J of electrical energy every 45 seconds. What is the power of the microwave oven?

• 150 W

• 675 W

• 1 500 W

• 6 750 W

Multiple Choice

An electric fan uses 9 000 J of electrical energy every 2 minutes. What is the power of the electric fan?

• 75 W

• 90 W

• 450 W

• 900 W

Multiple Choice

A television uses 360 000 J of electrical energy every 1 hour. What is the power of the television?

• 100 W

• 200 W

• 12 000 W

• 720 000 W