Power
P = E ÷ t
1. What is power
2. What is the power of an electric kettle if it transfers
20000J of energy 10s?
P=E ÷ t
P = ………. ÷ ……….
P = …………………W
10. Calculate the Energy transferred when an electric motor
for a lift has a power of 35kW and it takes 8s to move
between floors
3. What is the Power when torch transfers 80J of energy in
5s?
12. How long does it take for a 1000W heater to transfer
5000J of energy?
4. What is the Power of a cyclist if they transfer 100000J
during a sprint that lasts 20s?
13. An electric cooker transfers 200kJ of energy. On the
information sheet the cooker is listed as having a
maximum power of 2kW how long is the cooker on for?
11. Rearrange the equation to make time the subject
5. Convert this to kilowatts
6. What is the power of a crane that lifts 100kg, 24m up a
tower block if during this lift it transfers 4000kJ of
energy it took the crane 50s to compete the lift.
Killer Questions
Maximum power of a toy electric train is 20W. If 1500J are
transferred in 70s. Use this information to calculate if the
maximum power has been exceeded
7. Rearrange the equation to make Energy the subject.
If the power output was reduced to 15W and the toy train used
for 100s, does it transfer more or less energy than before?
8. Calculate the Energy transferred when an light bulb has a
power of 35W and is switched on for 60s
If the same toy train is run at maximum power for 30 minutes
and a charge of 10p is made for every 18000J transferred. How
much does it cost to run the train for this time?
9. Calculate the Energy transferred when the same light
bulb from Q8 is switched on for 6minutes