gravity and electromagnetism what are the similarities?

Answer 1

In addition to the forces between two sources (mass m and M or electric charge q and Q) being inversely proportional to the square of the distance between the two sources (F ~ Mm/r^2 and f ~ Qq/r^2), both set up force fields. For gravity, we have a gravity force field; for EM, we have the electric and magnetic force fields.

There are major differences, too. One such difference is that there is no such thing as a repelling gravity field. That is, gravity always attracts the two masses together. On the other hand, if both q and Q are negative or both are positive, the force f ~ qQ/r^2 will push the two sources away...they will repel each other.

Answer 2

Both forces scale as 1/r^2, where r is the distance between the two massive objects (in the case of gravity) or the two charged objects (in the case of electromagnetism).