Power and Efficiency

Power is the rate at which ________ is transferred.

What is the unit in which power is measured in?

• watts (W)

• kilowatts-hours

• joules (J)

• volts

1 kilowatt (kW) is equal to how many watts?

One watt is one joule of energy being transferred each second.

• True

• False

What is the power rating of an electric shower transferring 10 000 J/s in watts?

(choose 2 answers)

• 10 000 watts

• 10 watts

• 10 000 kilowatts

• 10 kilowatts

An electric kettle has a power rating of 3 kW. How much energy does it transfer each second?

• 3000 joules

• 3000 kilojoules

• 3 kilojoules

• 300 kilokoules

Which would have a lower power rating?

• kettle

• electric shower

The efficiency of an appliance is calculated by:

• comparing the useful and wasted energies

• measuring how much energy is transffered

• comparing the useful energy transferred to the total energy supplied

• comparing the wasted energy transferred to the total energy supplied

What is the name of the diagram we can use to show the energy transfers in an object?

• Sankey diagram

• Energy diagram

• Efficiency Diagram

• Watt diagram

How much useful energy is transferred?

• 1600 J

• 400 J

• 1200 J

• 2000 J