1. Power and electrical power
21st October
Power and electrical power
Objectives
Understand what power is.
Explain that the amount of electrical energy a device transforms depends on how long the appliance is switched on for and the rate at which the device transforms energy.
Be able to calculate the cost of electrical energy used.
Keywords: Efficiency, Power, Energy, Kilowatt, Kilowatt-hour
2 lessons

2. Power
What is power?
Power is the energy transferred in a certain time.
Power in Watts is the amount of Joules transferred in 1 second.
ENERGY
POWER ¦ TIME

3. Power Demo Height x weight = energy Energy/time = power Total height:
Time for walk:
Time for run:
Energy for walk:
Energy for run:
Power walk:
Power run:

4. Electrical Power In pairs:
Do questions from Milner Text book p including the remember box.
Time limit: 15 minutes
Peer mark.

5. Plenary – Stand Up, Sit Down
Watts
Joules
1Joule/second
Energy = Power x Time
400 Joules
2400 Joules (2.4kJ)
What is power of a device measured in?
What is energy normally measured in?
Define a Watt.
How can you calculate Energy?
A light bulb is marked "40W". How much energy will it get through in 10 seconds?
How much energy will the same light bulb get through in a minute?