Before I “define” what is potential difference. I would advise that you drop the following concepts or thinking.
Potential energy is always associated with a system of two or more interacting particles and not of any of the individual particles within the system. When a small ball moves near the surface of the Earth under the influence of gravity, the change in the configuration of the ball-Earth system comes about largely because of the motion of the ball, so we often associate the potential energy of this system with the ball alone. As a result, we would hear people saying like “gravitational potential energy of ball…” However, this tends to give the students the impression that the ball possesses gravitational potential energy. But this impression is NOT correct. The gravitational potential energy is actually shared between the ball and the Earth. This means that electrons
do not possess electrical potential energy.
An electrical component such light bulb that is connected to a battery does not get the energy from the battery via the movement of electrons! I believe in A-level physics, you would learn about drift velocity of the electron. The magnitude of the drift velocity is so small that it should give you some hints that the electrical energy cannot be transferred by electrons.
Avoid using the analogy to “understand” the concepts in the current of electricity. Why? The analogy only helps to you remember the result or the physics found in the current of electricity. All analogies have limitations. Some analogies are good in helping the students “see” the certain results, but students tend to generalise them to see other results. As a result, the students will be confused.
When you want to think of the potential difference between two points say A and B, link it to an electric field – the two points A and B are in an electric field.
The potential difference Δ
V =
VB −
VA between two points A and B in an electric field is defined as the
change in electric potential energy of the system Δ
U when a charge
q is moved between the points divided by the charge:
ΔV = ΔU/q
The change in electric potential energy of the system is associated with the negative work done by the electrostatic force on the charge.
Δ
U = −
WI assume that you know this relationship but this is unknown to you, let me know and I would explain in another post.
So we can also define the potential difference between two points in an electric field as the
negative work done by the electrostatic force to move
a unit charge from one point to the other.
Apply it to the circuit, we can define the potential difference across a component in a circuit as the work done to drive a unit charge through the component.