# electronvolt – what is electronvolt(eV) and how is eV related to Joule?

Last updated on April 12th, 2021 at 12:25 pm

The SI unit of energy joule is too large a unit of energy for the microscopic world. **A more convenient unit of energy for the microscopic world is the electronvolt, eV.** eV by the way is not part of the SI system.

## What is electronvolt? | Define electronvolt

**We define the electronvolt as the work done when a charge equal to one electron charge is taken across a potential difference of one volt.**

When a charge equal to two electron charges is taken across a potential difference of 1 V, the work done is 2 eV; moving a charge equal to seven electron charges across a potential difference of 5 V results in work of 35 eV, and so on.

## How to convert electronvolt to joule? | How electronvolt is related to Joule

Electronvolt is a convenient unit of energy and not an SI unit. The SI unit of energy is Joule. Hence, it’s a common interest to know the relationship between electronvolt and Joule.

To convert **eV** to Joule, we will use this formula: **W = qV**

An **electronvolt is the work done to take a charge equal to one electron across a potential difference of one volt**, so we will put the values of q and V accordingly in the equation.

**1 eV = 1.6 × 10 ^{−19} C × 1 V = 1.6 × 10^{−19} J**

**So the relationship between electronvolt( eV**)

**and Joule can be expressed by the equation: 1 eV = 1.6 × 10**

^{−19}J## Joule to electronvolt (eV) conversion

We know that **1 eV = 1.6 × 10 ^{−19} J**. From this equation we get Joule to electronvolt (eV) conversion easily as shown below:

**1 J = 1/(1.6 × 10**

^{−19}) eV## Where is electronvolt used?

**Electronvolt**(eV) is a unit of energy that is commonly used in atomic and nuclear physics.

## Can you convert electronvolt to Watt?

You can’t convert electronvolt to Watt, because electron-volt and Watt units represent different quantities. Electron-volt(eV) is the unit of energy and Watt is the unit of power.

## Can you convert electronvolt to Volt?

You can’t convert electronvolt to Volt, because electron-volt and Volt units represent different quantities. Electron-volt(eV) is the unit of energy and Volt is the unit of potential difference.

## Solving Numerical problems using eV

a) Determine the speed of a proton (m = 1.67 × 10^{–27} kg) that is accelerated from rest by a potential difference of 5.0 × 10^{3} V.

b) A proton with speed 4.4 × 10^{6} m s^{−1} enters a region of electric field directed in such a way that the proton is slowed down.

Determine the potential difference required to slow the proton down to half its initial speed.

**Solution:(a)**

## Summary

We have seen how to define eV and how it is related to Joule. We have also gone through a number of frequently asked questions related to electronvolt. We have seen how to solve a numerical problem related to eV for better understanding.

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