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What is a Coulomb?
A coulomb is a unit of electrical
Charge is given the symbol Q.
are tiny and have a very small
In the physics of electricity, we take a
very large number of electrons as 1 unit of charge
called a coulomb.
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.
What is Direct Current?
There are two different
types of power supply.
One type supplies alternating current
and the other type supplies direct current.
A cell or a battery supplies direct current.
With direct current,
leave from one side of
the cell, pass through all of the components in
the circuit and return back to the other side of the cell.
The electrons are given
energy by the power
and they then transfer this energy to all of the
components in the circuit. Electrons are not used up
by the components. The same number of electrons
leave from one side of the cell and return to the other.
What do we need to know about Coulombs?
We need to know
1. The rate of coulombs
flowing in the
The number of coulombs per second is called the current.
2. How much energy each coulomb has.
The number of joules per coulomb is called the voltage.
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