Electromagnetism created a revolution by leading to the devices called motors which convert electrical energy to mechanical energy. Experiments by scientists like Oersted and Faraday made a long leap by converting mechanical energy to electrical energy. When a straight conductor is moved in a magnetic field an electric current is induced in it and the phenomenon is electromagnetic induction. The emf caused is the induced emf and the current is induced current. Oersted found the same by relative motion of a magnet with respect to a coil. Faraday's experiment proved that the strength of the induced current depends on several factors like the strength of the magnet, the speed of motion of the magnet, its orientation, the number of turns in the coil and the diameter of the coil. The induced current can be detected by a galvanometer. Fleming’s right hand rule gives the direction of the induced current in a conductor when it is moved in a magnetic field. Transformers are based on this principle, which consist of a primary coil and a secondary coil. The number of turns in the coils is selected based on the type of the transformer to be made, namely, step-up or step-down.
Electric generators work on the same principle. They have an armature which is free to rotate in a magnetic field. Its terminals are connected to two slip rings, which are further connected to two brushes and they are connected across a load resistance through which the generated electricity can be trapped. The rotation of the armature in the magnetic field changes the magnetic flux in the coil of the armature and an electric current is induced. For every half rotation, the direction of the induced changes and hence called alternating current.
The current at the power plants is distributed through transmission lines at a high voltage and hence the lines are referred to as high tension power lines. At the substations these are stepped down to a lower voltage and supplied to houses at a low voltage. A domestic electric circuit essentially contains mains, a fuse, live or line, neutral and earth wires. From the poles supply cables bring the current to the mains. Within the house, all the equipments are connected in parallel combination.