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I LIVED happily without a microwave for 10 years, but, since acquiring one when I moved house last year, I have come to appreciate what a useful gadget it is. I have also realised that much of what I thought I knew about microwaves wasn’t quite right.

Microwave ovens work using electromagnetic waves, also called microwaves, with wavelengths of 12 centimetres or so – much longer than visible light, but shorter than most radio waves. Microwaves create an oscillating magnetic field that puts certain molecules in a spin: namely, molecules like water, which have positively and negatively charged portions. Anything containing such molecules is heated up by the waves. Other molecules absorb the energy less efficiently.

The rotating plate inside a microwave oven ensures that all surfaces of the food are equally exposed to the microwaves. But the waves lose energy as they pass through food, so anything more than 2 centimetres or so from the surface won’t heat up much. This means it is a myth that microwaves heat food from the inside out.

, or defrosting frozen food, takes longer than you might think because water molecules in ice are locked into a crystal structure and aren’t able to rotate.

Some people worry about standing near a microwave while it runs, but this is quite safe: the waves can’t escape the metal walls. Also, the door has a metal grid behind it and the waves are too big to fit through the holes.

As a child, I was told never to put metal in a microwave, but this won’t necessarily lead to disaster. When microwaves hit metal, most of the energy is reflected – so, if you try to warm up food in a foil container, the metal will shield the food and stop it heating up. However, microwaves can push electrons around in the metal, and when they collect on a jagged edge or the point of a fork, they may create a spark. So, it is still best not to put metal in a microwave, aside from some products such as microwave sandwich toasters, which are designed to be safe.

A typical microwave runs on about 1000 watts, meaning it uses about half as much energy as a conventional oven for each minute it is on. It heats food faster, too, so it doesn’t need to be used for as long. Cooking a jacket potato in the microwave requires than doing so in an oven. You can in a microwave, using about half as much energy as on an induction stove.

Perhaps the most joyful use for a microwave is to make a single serving of cake in a few minutes. In a large mug, mix the flour, sugar and cocoa powder, then mix in the egg with a fork. Add the milk and oil and mix again. Cook it in the microwave for 1.5 to 2 minutes and watch it rise out of the top of the mug like a ²õ´Ç³Ü´Ú´Ú±ôé – it will sink when you stop the microwave.

For other projects visit newscientist.com/maker.