How do I convert between eV and J

eV means electron volt - that is, it the amount of energy required for an electron to travel down (or up) a potential gradient with a potential difference of 1V. This energy, known as the work done, W, is given by W = q x V, where q is the charge and V is voltage. In our case the charge q = e = 1.602E-19 Coulombs and V = 1 Volt so the work done W = e x V = 1.602E-19 J. As a result 1eV = 1.602E-19 J.
As an example suppose you have calculated the energy, E, of a photon to be E = 3.97E-21 J. To convert this into eV first remember that 1eV = 1.602E-19 J. We can rewrite this as 1J = 1/1.602E-19 eV. Then simply replace J with 1/1.602E-19 eV to get
E = 3.97E-21 * (1/1.602E-19 eV) = 0.025 eV.

Related Physics A Level answers

All answers ▸

How do we know the energy of a photon (light particle) is quantised?


Use the kinetic theory of gases to explain why the pressure inside a container increases when the temperature of the air inside it rises. Assume that the volume of the container remains constant.


In the Photoelectric effect, Why does increasing the light intensity have no effect on the energy of the electron emitted?


In the Rutherford alpha scattering experiment, most particles passed straight through the foil with little or no deflection. What can be deduced about the structure of the atom from this?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo
Cookie Preferences