Electromagnetic Induction

Energy conversion

Motor and Generator

In the previous example, we learned that rotational movement can generate electrical current, but what about the reverse scenario? For example, if a current is flowing through the coil in a magnetic field, will the hand crank rotate?

The answer is YES.

As shown in the following figure, when electrical current passes through a coil, it generates a magnetic field. This field then interacts with the magnetic fields of nearby permanent magnets, leading to either attraction or repulsion. Such interactions can produce movement or exert a force thereby rotating the shaft, which is exactly how a motor works.

To visualize our conclusion experimentally, replace the bulb by a battery holder (need to install two AA batteries) that generates constant 3V. Once turning on the switch, the hand crank will automatically rotate by itself.

Do not rotate the crank when it is powered by batteries

The above motor experiment and the hand crank experiment you did in Section 1.4 both rely on the principle of electromagnetic induction for their operation. In a motor, electrical energy is converted into mechanical energy through the interaction of magnetic fields produced by the flow of current in coils and a magnetic field created by permanent magnets or other sources. Conversely, in a generator, mechanical energy is converted into electrical energy through the motion induced by an external force, which in turn induces a current flow in coils within a magnetic field, according to Faraday's law of electromagnetic induction.

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