- It has an AC supply (Alternating Current) meaning the current is constantly changing direction
- The UK mains supply is approx 230 volts
- The frequency is 50Hz
AC can be shown on an oscilloscope screen (basically a voltmeter)
If you plug in an Ac supply then you get a 'trace' on the screen that shows how the voltage changes with time.
The trace goes up and down in a regular pattern meaning that some of it is positive and some is negative.
The vertical height shows the input voltage and the horizontal width shows the time.