Download A2. Revision notes - Potential difference

REVISION NOTES
POTENTIAL DIFFERENCE
NATIONAL 5
If a charged particle is placed in an electric field, it
experiences a force.
This force makes the charged particle move.
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We can produce an electric field by applying different
voltages to two parallel metal plates.
A battery produces an electric field in a
wire. The electrons in the wire (charged
particles) can then move.
When a charged particle is moved by a field, it gains energy.
The amount of energy it gains depends on the difference in voltage between the
two plates, or between the two terminals of the battery.
This is called the potential difference, though we often just call it ‘voltage’.
So, potential difference is a measure of the energy given to charges in a circuit.
What is a ‘volt’?
A 3 V battery gives 3 joules of energy to each coulomb of charge that passes through
it.
A 12 V battery gives 12 joules of energy to each coulomb of charge that passes
through it.
So, one volt is the same as one joule per coulomb.
1 V = 1 J C-1
How the energy is used
The greater the potential difference, the more energy is given to the charges in a
circuit. As the charges move around the circuit, they give up their energy to bulbs,
resistors and so on.
The potential difference (voltage) across a resistor tells us how much energy is given
up. If the p.d. across a resistor is 4 V, then 4 joules per coulomb are transferred to
heat energy in the resistor.