Forms of Energy
Energy exists in different forms such as light, thermal, sound, kinetic, nuclear, electrical, gravitational potential, eleastic potential and chemical.
Gravitational potential, eleastic potential and chemical energy are all forms of stored energy.
Forms of energy and example:
- Light - from the Sun or a lamp.
- Thermal - Flows from a hot object to a colder object.
- Sound - a loudspeaker or your voice.
- Kinetic - anything moving.
- Nuclear - from neclear reactions.
- Electrical - whenever a electric current flows.
- Gravitational potential - stored in any object that can fall.
- Elastic potenial energy - stored in stretched objects such as elastic bands or springs.
- Chemical - stored in fuels, food batteries and released when chemical reactions take place.
Conservation of Energy
It's not possible to create or destroy energy. It is only possible to transform it from one type of energy to another, or move it from one place to another.
This means that the total amount of energy is always the same, this is called the conservation of energy.
For example when an object falls, gravitational potential energy is changed to kinetic energy. Similarly, stretching an elastic band transforms chemical energy into elastic potential energy. In a solar cell, light energy is transformed into electrical energy.
REMEMBER: Conservation of energy means changing one type of energy to another.
A device or machine is something that tranfers energy from one place to another or transform energy from one form to another.The energy suppiled to the device is called 'input energy.'
The energy we get out of the device consists of:
- Useful energy, which is transferred to the place we want and in the form we want it.
- Wasted energy which is not useful transferred or transformed (mostly its converted as heat, normally because of friction between the moving parts of the device.)
From the conservation of energy we know that input energy is equals the useful and wasted energy added together.
Both the useful energy and the wasted energy will eventually be transferred to the surroundings, and make them warm up. As it does so, it becomes more difficult to use the energy,
Energy and Efficiency
The unit of energy is the joule, simple J. This unit is used for all forms of energy. The less energy that is wasted by a device, the more efficiet the device is said to be.
We can calculate the effciency of a device using the equation: Effeciency = energy useful transformed by the device over input energy.
The effeiciency can be left as a fraction or multiplied by 100 to give a percentage. No device can be 100% effecient, except an electric heater, which usefully transforms all of the electrical energy suppiled to it into heat energy.