Electric Voltage


Electric voltage              
1 volt = 1 joule/coulomb= 1 newton-meter/coulomb

Voltage (or potential difference) is the energy required to move a unit charge through an element, measured in volts (V).

To move the electron in a conductor in a particular direction requires some work or energy transfer. This work is performed by an external electromotive force (emf), typically represented by the battery . 
This emf is also known as voltage or potential difference. The voltage between two points a and b in an electric circuit is the energy (or work) needed to move.

The voltage across an element (represented by a rectangular block) connected to points a and b. The plus and minus signs are used to define reference direction or voltage polarity. The Vab can be interpreted in two ways: (1) point a is at a potential of Vab volts higher than point b, or (2) the potential at point a with respect to point b is . It follows logically that in general
                                               Vab = -Vba

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