By varying the current i we are automatically varying the field B produced by A
An induced electromotive force can either originate from the variation of a magnetic field as a function of time, or from the action of a uniform magnetic field on a straight conducting wire. That is, it originates by the movement of a circuit. In this case, the variation of the magnetic field flux induces an electric field E at each point in space.
Whenever we verify that an induced electric current has arisen as a consequence of the movement of an electric circuit, this phenomenon is explained by the magnetic force. However, at times we will have difficulties in defining the induced electric current using the magnetic force. So, for such a definition, we will use Faraday’s Law as a basis.
In the figure above we have two circular shaped loops A and D. According to the figure, we can see that both loops are in parallel. In the figure above we can also see that loop A is connected to a generator (source) and to an electrical resistance of value R. If there is a variation in the electric current of the circuit above, we will see that the magnetic field B , generated by the loop A, will undergo changes in its flow.