AC and DC supply _ GCSE Physics

Electrical supplies can be direct current or alternating current. It's referred to as AC/DC but not rock band of course. If the current flows in one direction it is called direct current. Batteries supply DC current to most of your appliances at home like your mobile phone and laptop. On an oscilloscope screen, a direct current would look like this, boring I know. If the current constantly changes direction, it is called an alternating current. Mains electricity is an AC supply, with the UK mains supply being about 230V. AC supply also has a frequency, or how many times it changes direction and then back again in a second. In the UK the frequency is 50Hz. On an oscilloscope screen, an alternating current would look like this. You can calculate the period and frequency from an oscilloscope trace. The period is the time taken for one complete oscillation. You can find this by simply looking at the time before one peak and one trough or any two identical positions on the curve. The period in this case is 20ms. To work out the frequency, you divide 1 by the period in seconds. So in this case it would be 1/0.02s, which is 50Hz. What a coincidence, it's the same as the UKs power supply, it's almost as if I'd planned it.