Need desperate HELP working out units of electricity

[Bouncing]

I was doing physics GCSE core revision on bitesize and it says this for two questions

4. A 250W computer is switched on for 4 hours. How many Units of electricity does it use? Answer: 1

5. A 2 kW electric fire is switched on for 30 minutes. How many Units of electricity does it use? Answer: 1

I don't understand why it's 1 :S I searched all over the internet but it says 1 unit is 1 hour but it can't be. Can someone help me got a science modual next month!

[tm]

The answer units are kW/h.
Thousands of watts per hour.

So 250 watts for 4 hours would be the same as 1000 watts per hour, or 1 kW/h.
2000 watts for half an hour is the same as 1000 watts for 1 hour, or 1 kW/h.

Simple!

[DieselShaq]

I'm supposing that 1 "unit" of electricity is 1,000W, which in other words is 1kW. Using the equation E=Pt (energy = power * time), with power in Watts and time in hours, you can work out the energy used in the above questions:

4. 250W * 4 (hours) = 1,000W or 1kW
5. 2kW * 0.5 (hours) = 1kW or 1,000 W

So in both the questions above, the amount of energy used was 1,000W (or 1kW), which equals to 1 unit of electricity.

EDIT: Yep, according to this (http://www.moneymatterstome.co.uk/Interactive-Workshops/kwh.htm), 1 unit is 1kW/hour, or 1,000W/hour.

[Bouncing]

I'm supposing that 1 "unit" of electricity is 1,000W, which in other words is 1kW. Using the equation E=Pt (energy = power * time), with power in Watts and time in hours, you can work out the energy used in the above questions:

4. 250W * 4 (hours) = 1,000W or 1kW
5. 2kW * 0.5 (hours) = 1kW or 1,000 W

So in both the questions above, the amount of energy used was 1,000W (or 1kW), which equals to 1 unit of electricity.

EDIT: Yep, according to this (http://www.moneymatterstome.co.uk/Interactive-Workshops/kwh.htm), 1 unit is 1kW/hour, or 1,000W/hour.


I can always rely on people like you thanks i understand now :)

[DieselShaq]

No probs! Feel free to post more if you don't understand!