Potential Difference

What is Potential Difference?

Potential difference can be simply defined as the difference of electrical potential between two points. When two positive charges when brought close to each other, they repel. When two negative charges are brought close to each other, they also repel. But when a positive and a negative charge brought close together, they attract each other. When these two opposite charges are combined, they can be used to work. This is why we need a positive and a negative to light a bulb or run any electrical tool, equipment or home appliance. This ability of charged particles to do work is called an electric potential. Therefore, two opposite charges have a difference of potential or Potential Difference. The unit of potential difference (pd) is volt.

Unit of Potential Difference

The unit of Potential Difference (Volt) is named after Alessandro Volta. The volt is a measure of electric potential. Electrical potential is a type of potential energy, and refers to the energy that could be released if electric current is allowed to flow. One volt is defined as the difference in electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. It is also equal to the potential difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. The SI unit of work is the joule (J). The SI unit of force is the newton (N). The SI unit of distance is the meter (m).

W (joules) = N (newtons) x m (meters)


In the field of electronics, potential difference is commonly referred to as voltage and its symbol is V. In some cases, the symbol U or E for emf (electromotive force) is also used, but the standard symbol V represents any potential difference. This applies to the voltage generated by sources like battery or solar cell, and also to the voltage dropped across a passive electronic component such as a resistor.

The potential difference, also referred to as voltage difference between two given points is the work in joules required to move one coulomb of charge from one point to the other. The SI unit of voltage is the volt.

Volt Formula

Volt Formula

Types of Voltage

There are 2 types of voltage – DC or Direct Current and AC or Alternating Current.

DC – It is constant voltage. Here the electric charge (current) only flows in one direction. Sources of voltage like a battery or solar cell supplies DC voltage. Example – 12 VDC

AC – It is Alternating Current. Here electric charge (current) changes direction periodically. Sources of voltage like an AC generator supplies AC voltage. Example – 240 VAC.

Voltage Polarity

Suppose there are 2 charged points – Point A is Positively Charged (+) and Point B is Negatively Charged (-). Now, if we move A (+) closed circuit from A to B or vice-verse, it requires work. The difference between the two points is the voltage polarity. This voltage polarity is indicated by a positive sign (+) at A and a negative sign (-) at Point B.

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