# 2.02 Potential Energy.

After completing this section you should be able:

• To define the terms potential and potential energy.
• To recall that voltage is a measure of electrical potential.
• To calculate electrical potential, from the ratio of potential energy and charge.
• To recall that the electrical potential of charged particles is increased, when they move through a power supply (such as a battery).
• To recall that the electrical potential of charged particles decreases, when they move through a resistor, (because the resistor converts their electrical energy into heat).

## Potential energy and potential.

It is very difficult to describe electrical potential directly. It is easier to explain gravitational potential energy and gravitational potential first and then to make a comparison between the two.

## Energy.

Energy is defined as the ability to do work. This means that an object that has the ability to move or change in any way, has energy. We give different names to the types of energy that objects have, depending on the changes that occur. For example, the energy of a moving object, is called kinetic energy and the energy associated with changes of temperature, (and also change of state, melting , boiling etc), is called heat energy.

## Conservation of energy.

The law of conservation of energy, is one of the fundamental laws of physics. It states that energy cannot be created or destroyed. However, energy can be converted from one type to another.

## Potential energy.

The presence of kinetic energy is obvious, because we can see when an object is moving. However some objects still possess energy, even though there are no obvious visible changes occurring. e.g. A parked car is stationary, but there is chemical energy stored in the fuel in its tank. We refer to this type of energy as potential energy. We can think of potential energy as energy which is stored in a system, which can be converted at some later time, into another type of energy, such as kinetic energy etc.