About this blog

Physics can be difficult to learn, but this blog aims to help you get into physics by connecting your GCSE physics lessons with things you see in the world around you.

Friday, 21 October 2011

Compare the Meerkat

Those comparison websites are everywhere these days, with varying degrees of annoyingness I have to say. But when it comes to comparing electricity prices, or working out the amount your appliances use it’s pretty simple to do the calculations yourself, you just need a few tools to decode the information you’ll get from the companies.

We’ve previously come across energy being measured in Joules (J) but those canny electricity providers give their prices for kWh, that is, the price for an hour of electricity if you use 1000 Watts. It’s simple to convert Joules to kWh though using the simple equation:

Energy (in kWh) = power (in watts) x time (in seconds)
1 kWh = 1000 x (60 x 60)
            = 3 600 000J

Now where it gets tricky are all those crazy numbers and dials on the electricity meter, so it’s usually best to wait for a bill to arrive to get all the details off that. On there you'll find a current meter reading, a previous reading, the units used, plus the cost per unit. Nowadays when it’s all worked out you’ll also have a nice huge cost amount as well!

So, it’s simple to work out the price once you’ve got all the details:

Now let’s see how much it costs to run a lamp for 15 minutes. If you want to work this out for one of your items, have a look round it and check out the label. There should the a value on it in watts (W).

So now you have it, you’re as good as a price comparison site, if not better, since you can work out how much it costs to use any of your appliances in your own house! Well done little meerkat.

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