Question

How are a gravitational and an electric field similar?

Answer 1

Looking at the Newton's graviatational law:

$$F = G\dfrac{m_1m_2}{r^2}$$

and Coulomb's law:

$$F = k\dfrac{q_1q_2}{r^2}$$

one can notice, that in both cases the magnitude of the force of interation is directly proportional to the interacting chargers (gravitational $m_1,m_2$ and electrical $q_1,q_2$ respertively) and inversly proportional to the squared distance $r$ between these charges.