define potential difference between two points. explain with a diagram
Answers
The potential difference between two points is defined as:
Potential difference between two points in a circuit is the work done in moving unit charge (i.e. one coulomb) from one point to the other
The units for potential difference are Joules per coulomb, or volts. (1 volt = 1 Joule/coulomb).
Figure 2(a) shows the variation in the potential around the circuit. We can follow this by considering each section of the circuit in turn.
Along the connecting wire from the cell to B there is no resistance and so no loss of electrical energy or drop in potential.
In the resistors r and R energy is converted to heat and so the potential drops from B through to E.
From E to the cell there is no loss of electrical energy and so the potential at E is the same as that at the negative terminal of the cell – zero.
Figures 2(b and c) shows that when no current flows in a circuit there is no change of potential and therefore no potential difference between two parts of that circuit that are connected.
So if a charge Q moves between two points in a circuit that have a potential difference of V volts between them the energy gained (or lost) by the charge is given by the formula:
Electrical energy = Charge x Potential difference(Voltage)
Joules = Coulombs x Volts = Amps x Time x Volts
But since Q = It we have:
Electrical energy = ItV