# Electric Potential and Voltage

We have learnt that charges experience a force when placed in an electric field and we can say that this electric force performs work to move the charge between two points.

Electric potential is the work required to move a charge from a reference point to a specified point. Expressed in another way it can be thought of as the potential energy per unit of charge (energy per coulomb)

It is the difference in electric potential between two locations that is of particular interest to Electronic Engineers, and this quantity is known as voltage (or potential difference) which has the units of Volts [V].

Where V is voltage, E is the energy for the total charge Q.

Batteries are a common device we are all familiar with which feature a voltage rating which is the difference in potential energy a charge has when moving from one terminal to the other. There is a chemical reaction inside the battery which converts chemical energy into electrical energy to provide the rated voltage.

Shown below are the two common circuit symbols for a battery:

In schematics and schematic editor software, such as LTSpice which you will be introduced to later, voltage sources are commonly represented as shown below:

Other types of voltage sources include: Electric Generators which convert motion into voltage and Solar Cells which convert light into voltage for example.

### Examples:

1. What is the voltage delivered by a battery that supplies 8J of energy to 2C of charge?

2. What is the voltage drop across the component in the figure below?