1. Electric Potential.
If you understood the electricity section of the AS course properly, you already have a full understanding of Electric Potential. 6V
PD =2V
PD =3V
PD =1V
Potential here = 6V
Potential here = 0V
Potential here = 4V
Potential here = 1V
The potential was defined as..
The amount of energy carried by each coulomb of charge at any particular point in the circuit.
But this could equally have been stated as ..
The work done in moving 1 C of charge from the 0 V position to a particular point in the circuit.

2. Now consider a circuit with a long uniform resistor6V
Potential = 1.5 V
Potential = 4.5 V V
Potential here = 6V
Potential here = 0V
Potential here = 3 V

3. This circuit is identical to an apparatus which allows the electric field in a long trough of liquid to be investigated
12V
Equipotentials 9V 6V 3V
Field Lines

4. .... Or the electric field in the air between two parallel plates
+ EHT 4000 V -
Rules about Field Lines.
1. They always leave a charged object perpendicular to the surface.
2. They are always evenly distributed as they leave the surface, because the charge always distributes itself evenly on the surface .
3. The arrow on the field line points in the direction of the force on a positive point charge.
Rules about Equipotential lines.
1. They are always perpendicular to the field lines.
2. The distance between the equipotential lines increases as the distance between the field lines increases.

5. 2 point charges. Equal & Opposite 2 point charges. Equal & Same
2 point charges. Opposite.
Upper charge = 3Lower Charge
Single Positive Plate.
+3q -q
Exercise: Draw in equipotential lines for these fields.