# Motion of a charged particle

1. Jan 2, 2013

### dev70

hi PF, i got a question in my mind while studying electrostatics that
Will a charged particle loose its charge if it travels with a speed
a) Less than speed of light?
b) Close to speed of light?

2. Jan 2, 2013

### Staff: Mentor

No and no (They're actually the same question).
However, you may have to put work into the system to keep the particle moving, either because it's moving against an electric field or shedding energy by emitting electromagnetic radiation.

3. Jan 2, 2013

### Staff: Mentor

No, charge is an intrinsic property of certain particles. They cannot lose it much like they cannot lose their mass or spin.

4. Jan 2, 2013

### FeynmanIsCool

Charge is a conserved quantity!

5. Jan 3, 2013

### dev70

thank you all..but the way inertial mass increases of a body when it travels close to speed of light, will anything similar happen?

6. Jan 3, 2013

### Staff: Mentor

Not with charge, no.

7. Jan 3, 2013

### vanhees71

Neither charge nor mass increase in relativistic motion, because mass and charge are both relativistic invariants, i.e., scalar quantities.

8. Jan 3, 2013

### galleon

this is a somewhat old-fashioned view of mass, that is now considered to complicate matters unnecessarily.

it's better to use the word 'mass' to simply refer to the rest mass of an object, which is invariant, and get rid of this idea of mass changing with velocity.

mass is invariant, and so is charge.

9. Jan 3, 2013

### dev70

ok...i know that rest mass is constant and invariant. but if we consider a charged particle moving in a medium say gas wont it ionize the gas particles? And if it does it should loose charge i guess?

10. Jan 3, 2013

### Staff: Mentor

Yes, it can ionize the atoms of the gas it moves through, but no, it will not lose charge. Ions are formed when the particle collides with the atoms in the gas and knocks electrons out of them; we start with the charged particle and a neutral atom, and we end up with exact same charged particle, a positive-charged ion, and a stray electron.

11. Jan 4, 2013

### jfy4

The only way a particle can ''lose'' it's charge, in some sense of the word, is by screening. This can happen in a material, like any ole dielectric. There charge is hidden by the material being weakly conductive.

Oddly enough, the QED vacuum can be considered a dielectric, and so measured charge and the mass of a electron, say, are ''screened'' by virtual particle, anti-particle pair production. The ''bare'' charge and mass of a particle is never truly known, and in fact, becomes silly to talk about, since it is unphysical since it can't be measured.

12. Jan 5, 2013

### dev70

well..jfy4..would you please tell more about it. i just couldnt understand what you meant?