# Rest energy of the electron

1. Dec 14, 2014

### Mizies

Electrons in a particle accelerator reach a speed of 0.999c relative to the laboratory. Is the rest energy of the electron equal to zero?

2. Dec 14, 2014

### Staff: Mentor

The kinetic energy of an electron (or anything else, for that matter) at rest is zero.

The total energy of the electron, calculated from $E=\gamma{m_0}c^2$ or $E^2=(m_0c^2)^2+(pc)^2"$, is .511 511 MeV when the electron is at rest and greater when it is moving and the kinetic energy is non-zero.

[Edit - left the decimal point out the first time around]

Last edited: Dec 14, 2014
3. Dec 14, 2014

### Staff: Mentor

The rest energy of an electron is 0.511 MeV, regardless of how fast it is moving.

4. Dec 14, 2014

### Matterwave

.511MeV or 511keV bro, 511MeV is some ginormous electron.

5. Dec 14, 2014

### Staff: Mentor

:)

6. Dec 14, 2014

### Staff: Mentor

It's overweight even for a muon.

7. Dec 14, 2014

thanks..