How can the electromagnetic force be increased? What different things affect the magnetic strength?

The electromagnetic force is responsible for most of the interaction we see in our environment today. The EMF holds electrons in their orbit around the nucleus.

Factors that can affect a magnets strength include : heat, radiation, strong, electrical currents in close proximity of to the magnet

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom. 

The bergeron process.