Power is basically the amount of energy being used per second in a device. It is measured in Watts. A 100W light bulb uses 100J or energy every second. It can be calculated using the following equation...

Or, in the case of electrical circuits when you know the current and voltage, by this equation...

 

Charge - Higher

At a higher level, you also need to know about charge. This is a measure of the rate of electric current flowing through a circuit and can be found using the two following equations...

In the higher exam you will be given these equations and will be expected to use them to answer questions. You must make sure that you know the of all of the units as this will gain you marks!

For more information about power and charge and some worked examples click on the picture below to be taken to a website which revises this topic...

 

Or for further practice, click on the picture below to do some more practice calculations from www.testyourself.org.uk.