Power Ratings of Appliances
Science: KS3, topic 3.1.15
Power Ratings of Appliances
Every single electrical appliance will have a power rating. Power is measured in watts (W) or kilowatts (kW).
Working out power
- Power is measured in watts (W).
- Energy is measured in joules (J).
- Energy transferred from one energy store to another energy store is also called ‘work done’.
Power as a rate
- Power is the rate at which energy is being transferred.
- The more energy that is transferred in a shorter space of time, the greater the power rating.
Power equation
- 1 W is the equivalent of saying 1 J per 1 second.
- Power (W) = energy transferred (J) ÷ time (s).
- The equation can be rearranged as energy transferred (J) = power (W) × time (s).
Electrical appliances
- Electrical appliances have power ratings.
- Power ratings show the power of the appliance in watts (W).
- The more energy an appliance transfers, the higher the power rating will be.
Test yourself on Power Ratings of Appliances
What is the meaning of a watt?
Which of these units is correct?
How can we rearrange the following equation?
power (W) = energy transferred (J) ÷ time (s)A lamp transfers 600 J of energy in 60 s. A toaster transfers 600 J of energy in 20 s. Which appliance has the higher power rating?
A drill has a power rating of 800 W. A food processor has a power rating of 400 W. Both appliances run for the same amount of time. Which statement is correct?