What is voltage and how is it made?

Answer 1

Voltage is more formally and descriptively called electromotive force. It is an electromagnetic force which causes outer valence electrons in the atoms of an electrical conductor to be disclocated and move from one atom to an adjacent atom when the conductor is connected in a loop or electrical circuit. The common unit of electromotive force is the volt. An electrical source, either directly connected or magnetically coupled with the circuit, produces the electromotive force. A "voltage source" maintains a fairly constant voltage in a circuit when resistance and current varies. A "current source" maintains a fairly constant current when resistance and voltage varies.

A generator, is an inductive device that converts mechanical energy, usually delivered through a rotating power shaft, to electrical energy. A revolving magnetic field in a rotor induces voltage in stationary coils (stator). The rotor can be either an electromagnet or permanent magnets.

Batteries and fuel cells produce voltage by a chemical reaction in a special cell which produces an excess of electrons at one electrode incorporated in the cell, which becomes negative, and an absence of electrons at the other electrode, which is the positive pole.

A photovoltaic cell is a light sensitive device constructed of semiconductor materials that readily absorb photons and release electrons in response. Conductive plates on either side of the cell develop an excess of electrons at one plate and an absence of electrons at the other plate, with a resulting voltage across the plates.

Thermocouples consist of two dissimilar conductive materials that are joined together at a junction. If each side of the junction is at a different temperature, a voltage will occur across the two conductive ends of the thermocouple.