A crystal radio is the distilled essence of a radio. It has very few parts, it needs no batteries or other power source, and it can be built in a short time out of things you can find around the house.
The reason a crystal radio does not need any batteries is the amazing capabilities of the human ear. The ear is extremely sensitive to very faint sounds. The crystal radio uses only the energy of the radio waves sent by radio transmitters. These radio transmitters send out enormous amounts of energy (tens of thousands of watts). However, because they are usually far away, and we have at most a few hundred feet of wire for an antenna, the amount of energy we receive with the crystal radio is measured in billionths of a watt. The human ear can detect sounds that are less than a millionth of even that.
The above circuit shows a simple crystal radio. U can also add some capacitors to the above circuit, a capacitor in series with the antenna coil allows high frequency to pass through enabling better performance and reception. 
Instead of ear phone u can also use a telephone receiver to listen to channels.
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