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.
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).
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