What is Voltage?

  • Voltage is defined as the electric potential difference between two points in an electric circuit.
  • Potential (or electric potential) is the energy capable of doing some work(W). When we consider two charges, they have a difference of potential.
  • The volt (V) is a measure of the amount of work required to move an electric charge.


  • The unit of voltage is volt. It is designated by the symbol V or v (where V stands for voltage). The volt is named after the Italian physicist Alessandro Volta, who invented the first chemical battery.

Let’s take an example:

Consider two water tank at different heights. The water requires some pressure to flow from the upper tank to the lower tank. This pressure is the voltage which is required for the charges to flow from one point to another point to produce current.

If the potential difference between the two points is large, it is called a high voltage. Likewise, if the potential difference is small, it is called as a low voltage.

According to Ohm’s Law, voltage can be calculated in a circuit using the below formula


In the above formula V, I, R represents Voltage, Current and Resistance respectively

Voltage plays two roles in electronic circuits,

  • It is a measure of the potential difference across the standard voltage sources such as batteries. This potential difference is called electromotive force (e.m.f)
  • Another role is, it is used to denote voltage drop across passive components (resistors, inductors, and capacitors) which is produced due to the flow of current. Thus the symbol ‘V’ is used to denote either e.m.f of a voltage source or voltage drop across a passive component.

Current is directly proportional to voltage, it means higher the applied voltage, greater is the value of current and vice versa. No current will be produced if the applied voltage is zero.

Instruments for measuring voltages include the voltmeter, the potentiometer, and the oscilloscope.

  • In our house, we use 110 – 240 V (AC). The household electrical outlets offer 120V.
  • In flashlight batteries, 1.5 V (DC) is used.


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