Electromagnetism is one of the four fundamental forces of the Universe. The other three are the "strong" and "weak" nuclear forces that hold the atomic nucleus together, and gravity.

Electromagnetic force is the force between charged particles that accounts for electricity and magnetism, and is carried by photons. The Electromagnetic force is responsible for all observed macroscopic forces, except for gravity. The Electromagnetic Force also holds electrons near a nucleus, and is responsible for pulling atoms together into molecules.

The Electromagnetic force is approximately 1/100th the strength of the strong force. It was recently discovered that the Electromagnetic force and the weak force are different forms of the same fundamental force. It is now dubbed the "electroweak force."

Electromagnetics has long been known to humans and was possibly discovered first by the Chinese who found that a magnetized needle always pointed North. In the 19th century, James Maxwell unified the ideas of electricity and magnetism into four equations known as Maxwell's Equations. These equations are the basis for understanding the entire gamut of electricity and magnetism.

The force between two charged particles is given by: F = Q1Q2 / 4πε0r2

Where Q1 and Q2 are the charges on point charges 1 and 2 respectively, ε0 is the permittivity of free space (8.85x10-12 Fm-1)
Sometimes the equation is simplified to: F = kQ1Q2 / r2
Where k = 1 / 4πε0 = 8.988x109

This simplified version only works when the permittivity of the space the interaction is taking place in is equal to that of free space.

Here is an example, an electron and an alpha particle (helium nucleus) are seperated by 1 centimetre, the force between them is:
F = 1.6x10-19 x 3.2x10-19 / 4πε00.012
F = 5.12x10-38 / 1.11212379x10-10 x 0.012
F = 5.12x10-38 / 1.11212379x10-14
F = 5.12x10-38 / 1.11212379x10-14
F = 4.603x10-24 N, which is very small.

Suppose the seperation wasn't 1 centimetre, but 1 millimetre:
F = 1.6x10-19 x 3.2x10-19 / 4πε00.012
F = 5.12x10-38 / 1.11212379x10-10 x 0.0012
F = 5.12x10-38 / 1.11212379x10-16
F = 5.12x10-38 / 1.11212379x10-16
F = 4.603x10-22 N, which is 2 orders of magnitude higher for a 1 order of magnitude reduction in seperation. This is due to the inverse square law.

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