Power and Efficiency

What is the efficiency?

Tags

NGSS.HS-PS3-3

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

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

Tags

NGSS.HS-PS3-3

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

How much useful energy is transferred?

• 1600 J

• 400 J

• 1200 J

• 2000 J

Tags

NGSS.MS-PS3-3

NGSS.MS-PS3-4

NGSS.MS-PS3-5

How much energy is wasted as heat?

• 400 J

• 1600 J

• 1200 J

• 2000 J

Tags

NGSS.HS-PS3-4

How can you find the power of an appliance?

• see how hot it gets when switched on

• see what voltage it needs

• look for the efficiency label

• look for the power rating on the label