Voltage

voltage is Electric potential differences between points can be caused by static electric fields, by electric current through a magnetic field, by time-varying magnetic fields, or some combination of these three

A current is produced when an electron is forced from its orbit around an atom.

Any form of energy that dislodges electrons from atoms can be

used to produce current.

 Voltage Source 

The six most common voltage sources

1- friction

2- magnetism

3- chemicals

4- light

5- heat

6-pressure.

note :-

voltage may represent either a source of energy (electromotive force) or lost, used, or stored energy (potential drop)

Unit of Measurement

voltage  measured in joules per coulomb (volts).