How do you induction cookers work?

Induction cookers are a great example of electromagnetism in action.

Induction cookers exploit properties of pots made with some proportion of iron by heating the metal using a high frequency varying magnetic field. The frequency is tuned for the size of the pot, material and depth to penetrate the material.

The pots heat up because the changing magnetic field causes small electrical currents to be set up in the material of the pot. As the currents move in the material the molecules in the pot offer resistance to the current and heats up.

Magnetic materials in the pot such as iron can be made magnetic when a magnetic field is nearby. But the magnetic field from induction cookers is changing direction very rapidly. Changing the direction of the magnetic field means working to change the magnetic field of the pot, which causes the pot to heat up more.

Induction is a very efficient process as it only heats the material, but is used in other areas such as welding, melting metals and alloys and making tamper-resistance seals for medicine bottles.

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