Types of Energy
There are lots of types of Energy that we use every day:-
Kinetic (movement) Energy.
Gravitational Potential Energy.
Chemical Potential Energy.
All of types of Energy have one thing in common:-
"Energy can't be created or destroyed, only changed from one form to another"
This is known as the law of conservation of Energy.
All useful systems change Energy from one form to another. Below is some examples of the Energy changes in everyday systems:-
Energy and Power
In science, no matter the type, the Energy is measured in Joules. Energy has the symbol E and the unit J.
A light bulb might use 100 J every second.
A wind turbine might generate 1,000,000 J every second.
The Power of a system tell us how much energy is used every second and is measured in Watts. Power has the symbol P and the unit W.
A light bulb might have a Power rating of 100 W.
A wind turbine might generate a Power of 1,000,000 W.
All real-life systems waste energy in some way, they are not 100% efficient. Most of the waste energy is in the form of light, heat or sound.
For example -
A light bulb is used to light a room. However, a traditional light bulb works by passing a current through wire with a high Resistance until it heats up enough to glow, giving out light. This heat energy is not useful to the system and is 'lost' to the environment. The more wasted energy, the lower the efficiency of a system.
The efficiency of a system can be found using the following formulae:-
Example 1 -
A light bulb uses 100 J of Energy every second. If the light bulb gives out 70 J of heat energy and 30 J of light energy every second, what is the efficiency of the bulb?
Efficiency = (Eout / Ein) x 100
Efficiency = (30 / 100) x 100
Efficiency = 30 %