Question

What is the value of 1eV?
A.) \[16\times {{10}^{-19}}J\]
B.) \[1.6\times {{10}^{-19}}J\]
C.) \[1.6\times {{10}^{19}}J\]
D.) \[1.6\times {{10}^{-19}}erg\]

Answer 1

Hint: Recall the relation between work done (W), voltage (V) and charge (Q) i.e., \[\text{W=Q}\times \text{V}\]. By using this relation, you can get the value of the required quantity easily.

Complete step by step answer:

From the expression of energy, we can write the energy required or work done for crossing an electric field of total voltage V by a charge Q coulomb is given by, \[\text{W=Q}\times \text{V}\] coulomb-volt or joule.

Now we know that the charge of an electron is \[-1.6\times {{10}^{-19}}\]coulomb and consider it has crossed an electric field of total voltage V.

Then the total work to be done is,
(charge of electron) (1 Volt)
= \[-1.6\times {{10}^{-19}}\]coulomb 1 Volt
= \[-1.6\times {{10}^{-19}}\]coulomb-Volt
= \[-1.6\times {{10}^{-19}}\]joule
Hence, the correct option is B, i.e., \[1.6\times {{10}^{-19}}J\]

Additional Information:
We can define 1 electron-volt (1eV) as the amount of kinetic energy gained or lost by 1 electron accelerating from rest through an electric potential difference of 1 volt in vacuum.
So, 1eV has the value of charge of electron multiplied by 1 volt or \[\dfrac{\text{1joule}}{\text{1coulomb}}\]

The electron-volt is not an S.I. unit.
The electron-volt (eV) is a unit of energy whereas, the volt (V) is the derived S.I. unit of electric potential. The SI unit for energy is the joule (J).

Note: Students should try to memorize the relations between physical quantities but if they understand the whole concept that the energy required or work done by charge in crossing an electric field of total voltage V then students can easily find out energy required by putting the value of charge and potential difference and this way they will be capable to answer these type of relations easily.