Electricity

Coulombs

Electrons are very small.
In physics, we take a very very large number of electrons
as 1 unit of charge - called a Coulomb.
Charge is given the symbol Q.

1 Coulomb = 6.2 x 1018 electrons.
(This is 6.2 million million million electrons).
Such a large number of electrons can do useful things like light a lamp.

Think of Coulombs as though they are busses,
taking a large number of electrons (like passengers)
from one side of the cell, through all the components in the circuit,
and back to the other side of the cell.
The electrons are not used up but keep flowing around the circuit.

This is called direct current.

Direct Current
<img src="Direct-Current.gif" width="100" height="100"><br>
We need to know the rate of Coulombs flowing around the circuit
(how many Coulombs per second)
and how much energy each Coulomb has (how many Joules per Coulomb).