How does it work? - Microwave oven

How does it work? - Microwave oven

This animation demonstrates how microwave ovens work.

Technology

Keywords

microwave oven, microwave, household appliance, kitchen appliance, electromagnetic, magnetron, heating, water molecule, heat flow, wave, technology, physics

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Scenes

Microwave oven

  • door with protecting foil - It prevents radiation from escaping from the cooking cavity.
  • cooking cavity
  • case
  • control panel
  • power supply
  • turntable

Construction

  • turntable
  • control panel
  • fan - Its blades scatter microwaves entering the cooking cavity.
  • waveguide - It directs microwaves from the magnetron into the cooking cavity.
  • cooling fan - It removes the heat produced by the magnetron.
  • magnetron - It generates microwaves using electric current.
  • transformer - It changes the voltage of AC power to the value necessary for the magnetron.

How it works

Dielectric heating principle

  • water molecule - It is an electric dipole: H atoms are partially positively charged, while O atoms are partially negative. Microwaves make water molecules vibrate, thus the food gets hot.
  • microwave - It is an electromagnetic wave with a wavelength between 1 mm and 1 m. In microwave ovens the wavelength is approximately 12 cm.

Animation

  • fan - Its blades scatter microwaves entering the cooking cavity.
  • waveguide - It directs microwaves from the magnetron into the cooking cavity.
  • magnetron - It generates microwaves using electric current.

Narration

Microwaves are electromagnetic waves, just like light, but their wavelength is larger: it varies between 1 mm and 1 m. In microwave ovens, the wavelength is approximately 12 cm.

Water molecules are electric dipoles: hydrogen atoms are partially positively charged, while oxygen atoms are partially negative. Therefore microwaves, that is, the periodically changing electromagnetic field, causes water molecules to vibrate. The increase of kinetic energy causes an increase of temperature, therefore materials containing water that are placed in the microwave oven become hot.

The magnetron generates microwaves using electric current, which are directed into the cooking cavity by a waveguide. There they are scattered by the blades of a fan. Reflected by the inner metal walls of the cooking cavity, the waves enter food and make it hot.

The door to the oven is fitted with a protective mesh, which prevents microwaves from escaping from the cooking cavity. Without this protective layer, our tissues would also heat up while standing near the oven, which could lead to burns.

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