# Destruction of e-p pair:energy?

1. Jun 17, 2006

### Kolahal Bhattacharya

When a+q & a-q charges colesce together, the neutralization collapses the charge configuration & the electric field is gone.what is the amount of energy released?
Please note that it is a personal query-not homework

2. Jun 17, 2006

### Andrew Mason

It depends on how far apart they end up and how big (diameter) they are! What is the amount of work done by the charges in moving from infinity separation to the final state?

AM

3. Jun 17, 2006

### nrqed

The language you are using is not standard but I am assuming you are taking about an *annihilation* process (liek an electron-positron annihilation, say).

Well, energy is conserved. So the total energy released is simply the sum of the energies of the two particle annihilating (using the relativistic expression $E = \gamma mc^2$). *If* the two particles are initially at rest, then the energy released is 2mc^2 (notice that a particle and its antiparticle always have the same rest mass).