# Electric Voltage | Definition | Formula | Units | Types

Contents

## What is Electric Voltage

Voltage is the pressure from an electrical circuit’s power source (e.g. battery, generator etc.) that pushes charges (i.e. electric current) through a conducting loop. \\ It is defined as the electric potential difference per unit charge between two points in an electric field.

It can also be defined the work done in moving a charge from one point to another point in a wire or conductor. It is denoted by “V” or “E”. \\ Voltage is also known as Electric Pressure, Electric Tension, Electric Potential Difference or Electromotive force. There is a little bit difference between Voltage and EMF (Electromotive Force).

Mathematically It can be represented \\\;\;\;\;V = IR \\ Where I = Current in circuit or wire or conductor\\ R = Resistance of circuit or wire or conductor\\It can also be represented by \\\;\\\;\;\;\; V = \frac{Work\;done (W)}{Charge (Q)}\\\;\\ OR \\\;\\ \;\;\;\;V = \frac{Power (P)}{Current (I)}

## Unit of Voltage

Voltage is measured by SI Unit called Volt, denoted by “V”. The term volt is named after the Italian physicist Alessandro Volta who invented the first battery.

One Volt is amount of potential difference between two points that cause flow one ampere of current and dissipates one watt of power between these points. Mathematically \\\;\;\;\; Volt = Ampere x ohm \\OR\\\;\;\;\; Volt = \frac{Joule}{Coulomb}\\ OR \\\;\;\;\;Volt = \frac{Watt}{Ampere}.

## Types of Voltages

There are two types of voltages – Alternating current Voltage and Direct current Voltage.

Alternating current Voltage or AC Voltage:- It is voltage which changes its magnitude and direction continuously. The AC Voltage has frequency of 50Hz or 60Hz, that means it changes is direction 100 times or 120 times in a second. The frequency of AC voltage in India is 50Hz whereas in European countries it is 60Hz. The AC voltage is denoted by a wave symbol ~. The graphical representation of AC Voltage is shown below.

Direct current Voltage or DC Voltage:- The direct current (DC) voltage is a uni-directional that flows in only one direction and magnitude. It does not change its direction. It has zero frequency. The sources of DC Voltage are batteries. The DC voltage is denoted by dash with 3 dots (⎓) symbol. The graphical representation of AC Voltage is shown below.

## Difference Between Voltage and EMF ?

Voltage is the amount of energy required to move the unit charge from one point to another point in conductor or wire or circuit. In other words, voltage is the difference between electric potentials of the two points. It is always lesser than EMF (Electromotive force). It is denoted by “V”. Mathematically \\\;\;\;\; V = IR \\ “V” stands for voltage \\ “I” stands for current \\ “R” is External resistance (i.e. Resistance of wire or circuit or conductor).

Electromotive Force (EMF) Electromotive Force is the energy which produces and maintains voltage inside an active cell. Electromotive force is the voltage present at the ends of the source in the absence of current i.e EMF is the open circuit voltage. EMF moves a charge from one pole to another pole inside a source. It is always greater then Voltage. It is denoted by “E”.Mathematically \\\;\;\;\; E = I (R + r) \\ Where \\ “E” stands for Electromotive force \\ “I” stands for current \\ “R” stands for External resistance (i.e. Resistance of wire or circuit or condcutor) \\ “r” stands for internal resistance of source.

## Voltage Analogy

Consider a water tank placed at a certain height above the ground. There is a hose at the bottom of the tank as shown in the below image. The water tank is like a storage battery and the water in the tanks is equivalent to the electric charge. The water pressure at the end of the hose is equivalent to voltage or potential difference in an electric circuit. The flow of water is equivalent to the current.

Now if we increase the amount of water in the tank then more pressure is developed at the end of the hose. Similarly, if we drain a certain amount of water from the tank then the pressure created at the end of the hose will decrease and the flow of water also gets decreased. \\Similarly with increase or decrease of voltage, current also gets increased or decreased respectively.