Applications
Electromagnetic induction is important to humans because it is useful. SAT II Physics has
been known to ask questions about real-world applications of electromagnetic induction.
The two most common applications are the electric generator and the transformer.
The Electric Generator
The electric generator, sometimes called a “dynamo,” is a noisy favorite at outdoor
events that need electricity. It uses the principle of electromagnetic induction to convert
mechanical energy—usually in the form of a gas-powered motor—into electrical energy. A
coil in the generator rotates in a magnetic field. As the magnetic flux through the coil
changes, it induces an emf, creating a current.
The Transformer
The transformer converts current of one voltage to current of another voltage. A simple
transformer consists of two coils wrapped around an iron core. Transformers rely on the
property of mutual induction: the change in current in one coil induces an emf in
another coil. The coil with the applied current is called the primary coil, and the coil with
the induced emf is called the secondary coil.
The induced emf is related to the emf in the primary coil by the number of turns in each
coil:
Outside a power plant, a “step-up” transformer, whose primary coil has fewer turns than
its secondary coil, increases the voltage (emf) of the current that is transported along
power lines. Then, before the power enters your house, a “step-down” transformer, whose
secondary coil has fewer turns than its primary coil, reduces the voltage. The higher
voltage on power lines cutting across the countryside allows more electricity to be
transported quickly to urban centers. The lower voltage within your house renders the
electricity safer.
Key Formulas
Motional
Emf