An electromagnetic force is a physics concept that refers to a particular force, or influence, that affects charged particles. These particles may be positively or negatively charged. The force, which is carried via photons, is responsible for holding electrons and protons together in an atom, and holding atoms together in a molecule. We encounter electromagnetic forces daily; they are the reason behind attraction and repulsion of magnets and electrical charges, and they factor in chemical reactions as well.

Photons and virtual photons are the messenger particles of an electromagnetic force. Having no mass and as well as the ability to travel at the speed of light, photons are able to carry the force and attract electrons and protons together. Rather than pushing or pulling those particles with the electromagnetic force it carries, the force-carrying photon actually changes the character of the particles, thereby creating atoms and molecules.

The concept of an electromagnetic force is at the heart of the theory of electromagnetism, which explains the relationship between electricity and magnetism. Electricity and magnetism were once believed to be separate concepts, but James Clerk Maxwell changed all that back in 1873. He found magnetism and electricity to be more similar than previously thought. Magnetic poles, for example, come in pairs and attract and repel one another; electric charges have a similar duality. The relationship between electricity and magnetism can be seen when a compass is used next to an electrical source. Flipping a switch produces an electric current in the wire, which in turn produces a magnetic field that disrupts the compass needle.

Physics has four "fundamental forces." The electromagnetic force is just one of them. The other three are: the strong nuclear force, the weak nuclear force, and the gravitational force. Both the gravitational force and the electromagnetic force are forces that people encounter on a day-to-day basis. The electromagnetic force plays a role in friction. It is also central to Einstein's Theory of Special Relativity.

The strong nuclear force is the strongest of the four fundamental forces; the electromagnetic force is second strongest. It, along with gravitational force, has the longest range of the four fundamental forces. While this particular force can be seen practically everywhere, it only works on bodies with an electrical charge, either positive or negative. Neutrons, which have no charge, would be completely immune to it.

The electromagnetic force follows the inverse square law. The inverse square law means that the force's strength is inversely proportional to the square of the distance from the source of that strength. So, for example, if you move 5 units away from the source of the force, the intensity is reduced to 1/25th. Both the inverse square law and electromagnetic force can be proved by long and complex mathematical equations.