Microwave ovens: Explained.

 

Microwave ovens could be one of the greatest inventions of the 20th century. But how exactly do they work?

Let's explore the science behind it.

Microwaves:

            Microwaves are electromagnetic waves that fall in between radio waves and infrared waves on the electromagnetic spectrum.

Microwave Ovens:

            Microwave ovens use microwaves to heat the food while radio waves can be tens of kilometers long. Microwaves used in cooking are just about 12 centimeters from crest to crest.

With the frequency of 2.45 gigahertz, waves at these frequencies are absorbed by food molecules especially, the molecules of water. These water molecules have a positive and negative end same as a bar magnet with a North and South Pole. As the microwave changes its polarity, the polar molecules rotate at the same frequency millions of times a second. To line up with the changing field, all this agitation on the molecular level creates friction which heats up the food. But since, microwaves don't interact with plastics, glass, or ceramics, only the food is heated

So how does a microwave oven turn electricity into heat?

            Inside the strong metal box, microwaves are created using a device called a magnetron.

A transformer steps up the standard household electricity from the wall socket to around 4000 volts. This increased voltage heats up the cathode or the filament which is at the center of the device. A ring-shaped anode surrounds the filament and electrons are emitted as the filament heats up and rushed towards the anode or the positive terminal. The anode has slots cut into it called resonant cavities.

            Two ring magnets are placed above and below the anode, which generates a magnetic field that is parallel to the cathode. Normally when the filament is heated, the electrons which are negatively charged particles would rush out in a straight line towards an anode, which has a positive potential. However, due to the magnetic field, the electrons bend back towards the filament and follow a curved path. These electrons spiral as they leave the filament-forming an interesting pinwheel pattern.

As the charges on the cavities oscillate, the tip of the pinwheel spins which in turn creates microwaves in the resonant cavities.

            The microwaves are then transmitted into the compartment through a channel called a waveguide. These waves bounce back and forth off the reflexive mirror eventually penetrating the food in turn heating it up.

 

This was the working principle of a microwave oven.

Stay tuned.

Bye.