Final answer:
Electric motors convert electrical energy to mechanical energy, while generators convert mechanical energy to electrical energy. Both have similar constructions, but their primary difference lies in their input and output energy roles.
Step-by-step explanation:
An electric motor and an electric generator are devices that transform energy from one form to another. The primary difference between them lies in the roles of input and output energy. An electric motor converts electrical energy into mechanical energy. This happens by sending a current through a loop of wire that is placed within a magnetic field, which results in a torque that rotates a shaft. In contrast, an electric generator does the opposite, as it converts mechanical energy into electrical energy by rotating a coil in a magnetic field, thereby inducing an electromotive force (emf).
In a generator, when the frequency of rotation of the coils increases, the output emf also increases because the induced emf is proportional to the rate of change of magnetic flux with respect to time.
Despite their role differences, motors and generators often have similar constructions. When a motor's coil turns, it acts like a generator because the changing magnetic flux induces an emf in accordance with Faraday's law of induction. Thus, a motor generates emf just by the act of its coil rotating.