What is the interactions between the what?

Answer 1

The main one is that electric current, which consists of electric charges flowing along a wire, sets up a magnetic field around the wire. The field lines are circles, with the magnetic field at right-angles to the current. The magnetic field intensity at distance r from the wire is given in SI units by:

H = i/(2.pi.r)

The second is magnetic induction, in which a voltage is induced in a loop of wire if the total magnetic flux linking that loop changes. The voltage induced in the wire loop (in SI units) is:

V = d(flux)/dt.