There are two types of current: direct and alternating. In a direct current (dc), the flow of electrons is consistently in one direction around the circuit. In an alternating current (ac), the direction of electron flow continually reverses.
Electrons are negatively charged particles and they transfer energy through wires as electricity.
Since electrons are so small and one electron will not have much of an effect anywhere, it is more useful to refer to packages of electrons. One coulomb of charge is a package equivalent to 6,250,000,000,000,000,000 electrons.
When current flows, electrical work is done and energy transferred. The amount of charge flowing past a point in the circuit can be calculated using the equation:
charge flow = current × time
This is when:
One amp is the current that flows when one coulomb of charge passes a point in a circuit in one second.
A current of 1.5 amps (A) flows through a simple electrical circuit.
How many coulombs of charge flow past a point in 60 seconds?
= 1.5 × 60
= 90 C
How much charge has moved if a current of 13 A flows for 10 s?
= 13 × 10
= 130 C
How much current flows when 10 C passes down a wire in 2 s?
= 5 A
Charge will only flow in a circuit if the circuit is closed, or complete, and if there is a potential difference applied to the circuit either by using a power supply or a battery.