When a time$-$varying current flows through a coil, it induces a voltage across a second coil linked to the first by a magnetic field. The procedure for determining dot markings is based upon whether the direction of the magnetic field established inside of the coupled coils is based upon current flowing inside the coupled coils. The dot convention states that when the current enters the coil through a dotted terminal of a coil, the reference polarity of the voltage that it induces across the other coil is positive at its dotted terminal.