Dynamo: is a device for converting mechanical energy into electrical energy. An electrical conductor moves across a magnetic field and electric current is induced. There is a powerful field magnet; between the poles of which the armature is rotated. This mechanical energy is converted into electrical energy In the form of a current in the armature.

Hydel project: waterfalls flowing on turbines, which are power units working on the principle of the water wheel, convert kinetic energy into mechanical energy. The turbines are connected with the armatures of dynamos and electricity is generated.

Transformer: It is a device by which an alternating current is changed to a different voltage without any change in the frequency of the current. Step-down transformer decreases the voltage.

Ink-filler: A partial vacuum is created inside the rubber tube by raising the level of the ink-filler which causes atmospheric pressure on the surface of the ink in the ink-pot to push the ink into the tube.