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Fundamentals

What Is Electromagnetic Induction?

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Quick answer

Electromagnetic induction is a changing magnetic field producing a voltage in a conductor. Discovered by Michael Faraday, this phenomenon is the basis of countless technologies: the transformer, motor, generator and wireless charging.

What Is Induction?

When the magnetic field near a wire changes, a voltage is "induced" in the wire. The key is the change: a steady magnetic field produces no voltage — the field has to rise and fall.

How Does It Work?

If a magnet is moved inside a coil, a voltage appears in the coil. Likewise, a changing AC current through one coil induces a voltage in a neighboring coil — this is exactly how a transformer works.

Where Is It Used?

ApplicationRole of induction
TransformerEnergy transfer from one coil to another
GeneratorTurns motion into electricity
Electric motorTurns electricity into motion
Wireless chargingContactless energy transfer

The Link to Inductance

Induction is the phenomenon behind inductance: a coil opposes a change in its own current with the voltage it induces (self-induction).

Common Mistakes

  • Assuming a steady field: voltage appears only while the magnetic field changes; a stationary magnet produces none.
  • Running a transformer on DC: a transformer needs a changing field; pure DC doesn't pass through it.
  • Forgetting inductive kickback: inductive loads like relays/motors produce a high voltage when switched off; a protection diode is needed.

Frequently Asked Questions

What does induction require?+
A conductor and a changing magnetic field that intersects it.
Why doesn't a transformer work on DC?+
A transformer needs a changing magnetic field; since a steady DC field doesn't change, no voltage is induced in the secondary coil.

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