Current (Oxford AQA IGCSE Physics)

Current

• Electric current is defined as the rate of flow of electric charge

  • In other words, the size of an electric current is the amount of charge passing through a component per second

• Current is measured in amperes, which has the symbol, A

  • A current of 2 A means that 2 coulombs of charge passes through a point in a circuit every second

• Current flows from the positive terminal to the negative terminal of a cell

  • Note that this is the opposite direction to electron flow

Flow of charge

• The following equation links charge flow, current and time:

• Where the symbols:

  • Q stands for charge flow (measured in coulombs, C)

  • I stands for current (measured in amperes, A)

  • t stands for time (measured in seconds, s)

• You can rearrange this equation with the help of the formula triangle shown below

  • Cover up the quantity you need to find

  • The position of the other quantities tells you the operation you need to perform to find them

Charge flow formula triangle