Final answer:
A machine that converts mechanical energy into electrical energy is called a generator, which operates based on electromagnetic induction, inducing an electromotive force by rotating a coil within a magnetic field.
Step-by-step explanation:
The term that defines a machine that converts mechanical energy into electrical energy is a) generator.
Generators operate on the principle of electromagnetic induction, as defined by Faraday's law. They typically consist of a coil that rotates within a magnetic field, or a magnetic field that rotates around a stationary coil, inducing an electromotive force (emf) across the coil. This emf drives an electrical current when the generator is connected to a circuit. A common example of a generator is a dynamo, which is often used in conjunction with rotating mechanical machines such as water wheels or steam engines to produce electricity.
In contrast, an electric motor does the opposite: it converts electrical energy into mechanical energy. When a current runs through the motor's coils within a magnetic field, it generates a force that results in torque on the motor shaft, thereby creating mechanical work.