Energy Transfers
What is Energy?
It can be difficult to understand what energy is as there are so many different forms of energy which may appear to have nothing to do with each other.
| Kinetic Energy | Wave energy, e.g. sound | Gravitational Potential Energy | Electrical Energy | Chemical Potential Energy |
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A good definition is that energy is the ability to do work. ("What work is" is another question!). Energy makes thins happen. It can make things move or heat them up or lift them up.
All types of energy are measured in Joules (J). Remember 1,000J = 1 kJ ( 1 kilo joule) and 1,000,000J = 1 MJ ( 1 Mega joule)
Energy in Respiration
Our bodies need energy to move, to grow and to keep warm. In every cell in our bodies a chemical reaction take place called respiration. Food and oxygen are converted into packets of energy ( a substance called ATP ) that can be used to do the jobs that the cell needs them to do.
FOOD + OXYGEN --> CARBON DIOXIDE + WATER + ENERGY
Energy Transfers
One of the most important ideas in physics is the principle of conservation of energy. Energy cannot be created or destroyed, only transferred from one form to another.
Here are a few examples of energy being transferred.
| In a kettle electrical energy is transferred into heat energy. We use a lot of electricity in our homes because it is so easily transferred into other forms. | When we burn something chemical energy is transferred into heat energy and usually some light. | When this diver jumps his gravitational potential energy is transferred into kinetic energy. | A solar cell converts the energy in sunlight into electrical energy. | In a wind turbine kinetic energy is transferred into electrical energy |
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In many situations not all the energy is transferred usefully. One reason for this is friction. When surfaces rub together this produces heat energy. In the wind turbine, for example, friction in the bearings will produce heat. Air resistance is a form of friction and will affect the amount of kinetic energy gained by the diver, if only slightly in this case.