UNDERSTANDING ENERGY

Physics says: If a body is moved to some distance by a force, work is said to done. The capacity to do work is energy. In short, the amount of work that can be done gives the measure of energy.

A body at a height can fall down (does work). So it said to posses "potential energy".
A fast moving body can hit another body and do some work. So it has "kinetic energy".

In a chemical battery, oxidation takes place in the negative end and the reduction takes place at the positive end. Hence the electrons are pulled from the negative to positive through a wire and the electric current is established. Here chemical energy turns into "electrical energy".
If the electric current flows through a coil of wire, magnetic field is established. This magnetic field can repel and attract another magnet. So motions will be created. Here electrical energy turns into mechanical energy.

In a chemical reaction, when a molecular bond is broken, energy is utilized. When the atoms form molecule, energy is released. Hence in a chemical reaction the net energy is released. This concept is used in the following energy conversions.
1. Petrol can burn, produce heat, gases expand, pushes the piston of an engine and does some work. Here "chemical energy" turns into the "heat energy".
2. The glucose in the food is converted into energy which fuels muscle contractions. The ATP molecules in our body stores and carries the energy. The heart beats and pumps the blood using the food energy.

Let light photons hit on the materials like zinc, electrons are knocked out from zinc atoms. The ejected electrons can flow through the wire and form current. So even ordinary light carries energy.

Finally, energy means work. Work means particles should be moved to some distance. This fact is true in all the above cases.

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