Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thebrain13 on 29/01/2007 06:15:59

Title: electric charge and motion
Post by: thebrain13 on 29/01/2007 06:15:59

If two positively charged objects were moving towards one another, would the strength of charge increase, relative to two stationary charges? what if they were moving away from each other or what if they were moving but not radially?

Title: electric charge and motion
Post by: daveshorts on 29/01/2007 17:09:54

If you are talking about a relativistic effect, yes there would be a change in the strength of the charges, but we call this effect magnetism. Y

Title: electric charge and motion
Post by: thebrain13 on 31/01/2007 23:14:38

Would the decrease in charge when objects are moving away from each other be greater than the increase in charge when they are moving towards one another?

Title: electric charge and motion
Post by: Soul Surfer on 31/01/2007 23:56:56

Lets get down to a bit more detail.

Isolated localised stationary electric charges have an inverse square law of attraction  between opposing charges and repulsion between similar charges just like gravity (except that gravity is always attractive)  when electric charges are moving that is like an electric current flowing and this creates a magnetic field at right angles to and around the direction of flow of the electric current  a bit like a right handed screw thread.

In general these effects are not dependant on high velocity  although the higher the velocity the stronger the effect.  one of the best ways of seeing the electromagnetic effects of current flow on gases is to look at the behaviour of solar prominences or  watch a thunderball (plasma light globe)  the effect of the self generated magnetic fields on the current flow through the plasma is to cause strands to pinch themselves into fine lines.

If the voltages are extremely high so that velocities become relatavistic the reletavistic effects are mostly associated with the fact that as things move faster the become heavier and more difficult to accelerate or go round corners so this acts against the pinching effect mentioned in the last paragraph.

Title: electric charge and motion
Post by: thebrain13 on 02/02/2007 20:25:55

But the change in momentum for the non intertial charge is less relative to the change in momentum for the inertial one. The "acting more sluggish" is not due to einsteins addition of velocities where momentum would always be conserved, right?

Title: electric charge and motion
Post by: Soul Surfer on 02/02/2007 23:51:11

Sorry I don't understand what you have just said please describe it in a different way.

Title: electric charge and motion
Post by: thebrain13 on 04/02/2007 22:08:13

What I meant was, lets say an object was traveling at .9c away from you. If you pushed it at this speed, it would be more massive and respond less to your push velocity wise. It would take more energy to increase its velocity the same, than it would to increase its velocity if it were stationary, but its momentum would increase as much as time and force would normally dictate. Magnetism is different, the moving charges apply less force to the stationary ones, and the momentum change from the new force (magnetism) causes the momentum to not increase as much as newton expected.