# If I have Volts, and I need eV, how do I get that?

1. Dec 30, 2005

### April30

If I have Volts, and I need eV, how do I get that?

Is eV (energy format) = V (voltage format), so that if I have a value given in volts, I know that it would be the same in eV units?

I know this is a dumb question, sorry guys...

2. Dec 30, 2005

### Chi Meson

eV is a unit of energy. It is exactly the amount of kineitic energy that one electron would obtain if it accelerated across one volt of potential difference. You do not convert eV to volts. You convert eV to joules.

Since potential difference is defined as the energy per unit charge ratio you will get a unit of energy when you multiply a unit of charge times a unit of potential, hence "electron-Volt"; here the charge is the fundamental charge of the electron. A joule (unit of energy) is equivalent to a "coulomb-volt." Since 1.602 x 10^-19 coulombs is the charge of an electron, then 1eV = 1.602x10^-19 joules.

3. Dec 31, 2005

### April30

Thanks Chi,

yeah I suppose I will simply look at eV as the work function of a metal. i just had a mental block ;)

4. Dec 31, 2005

### Chi Meson

The work function of a metal is an amount of energy. Any amount of energy can be expressed in eV. When doing the photoelectric effect, the energy of the photon is also measured in eV, and the maximum KE of the electron is again measured in eV. Any of these amounts of energy could just as well be measured in joules, kilowatt-hours, ergs, or any other unit of energy. The eV just happens to be an appropriately small unit of energy.