Question

How do you convert joules to electron volt ?

Answer 1

Hint: Learn the definition of 1J and the definition of 1eV. From the definition of the units explain the conversion technique used to convert Joules to electron volt. 1J of work is equal to the one volt times one ampere of current.

Complete step by step answer:
We know that the 1J of energy is used by a circuit if between 1V of potential difference a 1C charge flows. It can also be defined as the energy required or energy loss by a circuit if between 1V of potential difference a 1A current flows in one second.

Now, electron volt is the unit of work when only a single electron passes through a potential difference of 1V per second. The energy required to move a single electron through a potential difference of 1V is said to be the energy of 1eV. Now, only a single unit of electron contains a charge of $$-1.602\times {10}^{-19}C$$. Hence, the energy required to carry a single electron through a potential drop of 1V is,
$$1.602\times {10}^{-19}C\times 1V=1.602\times {10}^{-19}J$$
This is equal to 1eV, which means the basic unit of electron volt.
So, $$1eV=1.602\times {10}^{-19}J$$

So, when we convert joules to electron volt we divide the energy in Joules by the number $$1.602\times {10}^{-19}$$ to convert it to electron volt.

Note: The unit electron volt is used for energy related to molecular levels. The eV unit is a quantized unit since it only takes integral values of it, since there is no charge which has a charge less than or fraction of electronic charge. So, naturally we use the integer type value only when using units in eV.