# Question regarding charge

Discussion in 'General Electronics Chat' started by mrpewty, Jan 8, 2005.

1. ### mrpewty Thread Starter New Member

Jan 8, 2005
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I have a question that I think relates to the relationship between voltage and charge. A statement in an essay about x-rays states that:

"If the voltage between the cathode and the anode = V, then the kinetic energy of an electron with charge e = Ve"

Can anyone expand on that and help me understand why this is so?

2. ### Brandon Senior Member

Dec 14, 2004
306
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Image voltage as velocity and electron charge as mass. E=mv.

An electron has a charge. This charge is how well it will be attrtacted or repulsed by an electric field. If the electric field is increased, the electron will have more force. If the electrcons charge is increased, it will have more force and so on.

Have you noticed yet that EVERY formula for kinetic energy is the same as an electric formula for energy yet? ie gravity between 2 masses is the same formula as the force between 2 charged particles. Its all nearly the same concept your just in a new medium.

3. ### beenthere Retired Moderator

Apr 20, 2004
15,815
282
Hi,

That is an odd statement. The electron is a definition of charge, and nothing changes that. The electric charge carried by each electron is not variable.

Because the electron has an electric charge, a potential difference between electrodes will accelerate any electron (through a vacuum). But the kinetic energy possesed by the electron as a result of the acceleration is based on its mass, not its charge. If electrons had no mass, a linear accelerator would need to be only several inches in length. The charge on the electron is only the handle that the electric field uses to move the particle. The charge is not affected by the acceleration.

In a CRT, the energy of the electrons coming from the cathode is transferred to shell electrons in the phosphors. As they fall back to rest orbitals, they shed their acquired (and now excess) energy as photons at specific energy levels that we perceive as different colors of light. No electron's charge is altered in this process.

4. ### Brandon Senior Member

Dec 14, 2004
306
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I know my explanation was a bit odd, but I was just attempting to show the interelation between electrical formulas and kinetic formulas. The concepts are the same with just a set of different rules and constants to use and I was hoping he would see that and be able to make the connection he wasn't getting.

5. ### beenthere Retired Moderator

Apr 20, 2004
15,815
282
Hi,

I was being concerned by the electron's gain of mass with velocity. That won't affect charge, but has a lot of affect on KE as velocity gets into relatavistic area.

6. ### mrpewty Thread Starter New Member

Jan 8, 2005
2
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Thanks for the prompt replies people. It's given me things to think about that's for sure.