Electrical Engineering ⇒ Topic : Voltage

VOLTAGE

According to the structure of an atom, we know that there are two types of charges: positive and negative. A force of attraction exists between these positive and negative charges. A certain amount of energy (work) is required to overcome the force and move the charges through a specific distance. All opposite charges possess a certain amount of potential energy because of the separation between them. The difference in potential energy of the charges is called the potential difference.

Potential difference in electrical terminology is known as voltage, and is denoted either by V or ii. It is expressed in terms of energy (W) per unit charge (Q); i.e.

dw is the small change in energy, and

dq is the small change in charge.

where energy (W) is expressed in joules (J), charge (Q) in coulombs (C), and voltage (V) in volts (V). One volt is the potential difference between two points when one joule of energy is used to pass one coulomb of charge from one point to the other.

 VOLTAGE

Energy is required to move a charge from one point to another. If W joules of energy is required for moving charge Q from point A to B, the voltage V between A and B is given by

where 1 volt = 1 joule/1 coulomb

The unit of voltage is volt (V).

In Figure 1 (a), terminal A is +8 V above terminal B. In Figure 1(b), terminal B is  - 8 V above terminal A or in other words +8 V below A. Also it can be written as V_AB = +8 V [Figure 1(a)] and V_BA = - 8 V [Figure 1(b)[ by using double subscript notation and in general V_AB = - V_BA . V_AB can be expressed as V_AB = V_A - V_B and V_AB means that voltage of A with respect to B

                                                                         Figure (1) Two equivalent voltage representations