A charge of .4 C moves from point A to point B. 20.8 Joules of work are done on the charge. What is the potential difference in Volts from A to B?
A Volt is a measure of work per unit charge, measured in Joules per Coulomb. When a field does 20.8 Joules of work on .4 Coulombs of charge, the potential difference is ( 20.8 J)/( .4 C) = 52 J/C = 52 Volts.
If a charge Q (measured in Coulombs) moves from one point to another, requiring work `dW (in volts, or Joules / Coulomb), then the potential difference between the points is `dV = `dW / Q (the number of Joules divided by the number of Coulombs).
The figure below shows a charge Q moving from a low potential V1 to a high potential V2. The potential difference is `dV = V2 - V1, and the work required to move the charge is W = Q `dV (`dV is measured in Joules of work required per Coulomb of charge, so work must be the product of Q (Coulombs) and `dV (Joules / Coulomb) ).
It follows that `dV (the number of Joules/Coulomb) is obtained by dividing `dW (the work in Joules) by `Q (the charge in Coulombs).
"
