# Energy Transfers and Work Done

## Energy Transfers

Energy is never used up. When a system changes, the energy only transfers between energy stores. Keep in mind that a system just refers to an object or objects.

Four ways that energy can be transferred are:

• Mechanically – The action of a force to move an object across a distance
• Electrically – By an electrical current
• By radiation – Electromagnetic waves
• By heating – Conduction, convection and radiation

You may see the terms mechanical work and electrical work. ‘Work’ is another way of saying energy is transferred.

### Energy transfer by heating

During the heating process, energy can be transferred from a hot object to a cooler one by conductionconvection and radiation.

Conduction: Energy is transferred by direct contact.

Convection: Particles with more thermal energy take the place of particles with less thermal energy.

An example of this is when boiling water. The chemical energy store of the fuel decreases and the thermal energy store of the beaker and boiling water increases. Here, chemical energy is transferred to thermal energy.

## Energy Transfer Diagram

Energy transfers and the locations of energy stores can be shown in an energy transfer diagram.

Let’s look at the energy transfer diagram of an electric lamp.

This diagram shows the transfer of energy in an electric lamp. The battery is a store of chemical energy, which is transferred to the lamp using wires, which then transfers to the surroundings as light.

The useful energy is the energy transferred as light (because we use lamps to light up a place). However, there are also some non-useful energy transfers, such as the energy that is transferred to the surroundings as thermal energy.

The total energy before and after a change or transfer remains the same, this is known as conservation of energy.

So: Total energy before = Total energy after

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