# Electron volt or eV

Contents

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Key learnings:
• Definition of Electron Volt: An electron volt is defined as the energy needed to move one electron against an electric field of one volt.
• Power Calculation: Power (W) is calculated as the product of voltage (V) and current (I).
• Energy Expression: Energy is calculated as the charge (q) in coulombs times the voltage (V).
• Charge of Electron: The charge of an electron is -1.6 × 10^-19 coulombs.
• Applications of Electron Volt: Electron volts are used for various energy calculations at atomic and electronic levels, as well as for thermal and light energy.

The concept of the electron volt is simple. Let’s start with the basics. The unit of power is the watt.
W = VI, where V is the voltage and I is the current.
Current (I) is the rate of charge transfer. Therefore, the instantaneous power can be expressed as:

Here, q(t) is the amount of charge transferred over time t.

Now energy is expressed as

Where, q is the charge in Coulomb crosses a voltage V volts.

From the expression of energy we can write the energy required or work to be done for crossing an electric field of total voltage V by a charge Q coulomb is QV coulomb – volt or joules. Now we know the charge of an electron is – 1.6 × 10-19 coulomb and consider it has crossed an electric field of total voltage 1 V. Then the total work to be done is charge of electron × 1 V.

This energy amount is known as an electron volt, a micro unit of energy.

## Definition of Electron – volt

One electron – volt is the unit of energy in joules which equals to the amount of work to be done for bringing one electron against an electric field of potential difference 1 volt.
This is very tiny or micro unit of energy mainly used for different calculation in atomic and electronic levels. The concept of energy levels in the materials is dealt with this micro unit of energy that is electron volt. Not only the energy of electrons, this unit is also used for all types of energy like thermal, light etc.

### Video Presentation on Electron volt or eV

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