A crank powered torch

In desert areas of Africa where there is no electricity the Bedouins on camels carry with them colourful boxes of the size of a CD-player equipped with a crank. The crank is difficult to turn, but if you manage to turn it you can listen to the radio for some time. The box contains a generator similar to the one placed in this torch with a push-in handle. If you push it several times a magnet inside starts to rotate and creates electricity in the coil and the bulb glows.

The principle of operation of this torch is the same as in a huge power plant. An external force - a hand, or turbines powered by steam or water moves magnets or a coil and create electricity. This phenomenon is called electromagnetic induction and was discovered by Faraday.

The other torch is not equipped with a crank. Shaking the torch up and down you move a magnet through a coil inside and the bulb glows. (The manufacturer from China fitted the torch with two small batteries just to be sure).