Physics
Light houses are places with powerful lights to :

Guide and help large crowds at religious gathering during nights
Guide and warn the ships coming from different directions in the ocean
Indicate to the incoming warships, the location of a harbour during night
Guide and resolve traffic jams in crowded metro-cities during nights

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Physics
A dynamo is a device which

Creates mechanical energy
Converts electrical energy into mechanical energy
Creates electrical energy
Converts mechanical energy into electrical energy

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