## 2008-10-09

### The relationship between electric current and potential difference

Potential difference

A gravitational analogy can be used to explain electric potential difference. Moving a positive charge against the direction of an electric field is like moving a coconut upwards within Earth’s gravitational field. Both movements require work down by an external force. This work would in turn increase the potential energy of the object.

An object will move from a place of high potential energy to a place of low potential energy. The potential energy of water at the top of a waterfall is greater than at the bottom.

As a result, water flows from the top to the bottom of the waterfall. Similarly, positive charge will move from a point which has a higher electrical potential to a point which has a lower electrical potential.

The potential difference, V, between two points in a circuit is defined as the amount of work done, W, when one coulomb of charge passes from one point to the other point.

Potential difference = work done / quantity of charge or amount of work done is W = QV

The SI unit for potential difference is volt, V.

One volt is one joule of work done to move 1 coulomb of charge from one point to another in an electric field.