# Planck's Constant Conversions: J s to eV s

1. Jun 2, 2009

### JayBird

So, my physics final is tomorrow, and for the test we are given a list of constants. On this list is Planck's constant as 6.626x10^-34 J s. Now, that's all well and good, but they don't give it to us in eV s! And we need it in eV s for some of the problems. Given that we also get 1u=931.5MeV=1.66x10^-27kg, is there any way to convert it from J s to eV s? Thanks!

2. Jun 2, 2009

### kbaumen

1 eV is an amount of energy required to move an electron over 1 volt potential difference. Since qU = W, where q is the charge, U is the potential difference and W is the potential energy it acquires in respect to the initial point, an electronvolt is (charge of an electron) x (1 volt) = (answer in Joules) (since 1J = 1Cx1V). Therefore, 1eV is roughly 1.6 x 10^-19 J.

3. Jun 2, 2009

### JayBird

So I divide it by the charge of an electron? Thanks!!!

4. Jun 2, 2009

### kbaumen

Yes. To get joules from electronvolts, you divide electronvolts by the charge of an electron.