How Induction Cookers Work

Introduction

Induction cookers use electromagnetic principles to cook food without heating themselves.
Key concept: Eddy Currents.

Induction cookers have a coil at the center that generates a magnetic field when current flows through it.
The current is alternating (AC), causing the magnetic field to fluctuate in direction and strength.
The magnetic field itself does not produce heat.

When a conductor (e.g., a vessel) is placed on the induction cooker, the changing magnetic flux induces currents in the conductor's surface, known as Eddy Currents.
Eddy currents generate heat due to the resistance of the material.
The vessel heats up and transfers this heat to its contents (e.g., water).
The cooker's base remains cool because the human body is not a good conductor and does not generate significant eddy currents.

Faraday's Law: Changing magnetic flux through a conductor generates an electromotive force (EMF), inducing a current.
In a solid conductor, such as a metallic plate, eddy currents swirl in loops on the surface, causing heating.
Eddy currents are named for their swirling motion, similar to water eddies or whirlpools.

Heating: Induction cookers heat vessels through eddy currents, making them efficient for cooking.
Safety: The cooktop itself stays cool, reducing burn risks.

Sometimes, eddy currents are undesirable, as they can cause unwanted heating.
Increasing Resistance: One way to reduce eddy currents is by increasing the resistance of the conductor (e.g., introducing slots or lamination).
Transformer Application: In transformers, laminating the metal core reduces eddy currents and heat losses.

Magnetic Levitation: Eddy currents induced in an aluminum ring cause it to levitate above an electromagnet. The fluctuating magnetic field repels the induced magnetic field in the ring.
Maglev Trains: Eddy currents are used in magnetic levitation trains (Maglev) to reduce friction and achieve high speeds.
Pendulum Example: A pendulum with an aluminum plate slows down in a constant magnetic field due to eddy currents, illustrating electromagnetic braking.

Eddy currents can be harnessed to slow down moving objects, a principle used in electromagnetic braking systems (e.g., trains).
Experiment: A spinning aluminum disk slows down when a magnet is brought close, demonstrating the braking effect of eddy currents.

Eddy Currents: Currents formed on the surface of a conductor due to changing magnetic flux.
Applications: Heating, levitation, braking.
Reduction: Achieved by increasing resistance through slots or lamination.
Importance: They have practical applications in various fields due to their unique properties.