there are flash lights, which do not need battery to work. then how do they work? what is basically the principle behind this?

Asked by Simran Dhingra | 7th Sep, 2010, 12:00: AM

Expert Answer:

These battery-less flashlights exploit the energy conversion mechanism. They convert some form of energy into electrical energy and store this electrical energy in capacitors.

One type of dynamo-powered flashlight has a winding crank connected to a small electrical generator that charges a capacitor. Others generate electricity using electromagnetic induction. They use a strong permanent magnet that can freely slide up and down a tube, passing through a coil of wire as it does. Shaking the flashlight will charge a capacitor or a rechargeable battery that supplies a current to a light source.

Answered by  | 7th Sep, 2010, 06:45: PM

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