How does charge behave in a moving object?

[atmost20characters]

Specifically, if I had a sphere or cylinder that accelerated upward or downward, it's clear that the distribution of charge, rho, would shift. However would the density turn into some function of increasing rho as the radius increases? I assumed that the density of charge would basically turn into a blob and I'd need to integrate the non uniform surface of charge then, but I'm making a lot of assumptions I'm not confident with. Would appreciate any help!

 

[BvU]

Hello Max20,

it's clear that the distribution of charge, rho, would shift

Could you explain that, if it is so clear ?

 

[atmost20characters]

Hello Max20,
Could you explain that, if it is so clear ?

The specific scenario given was a sphere with uniform charge density is placed in an elevator, so I suppose the charge distribution would change if the sphere was a conductor? so then the charge would be on the outer surface of the sphere. This is why I was unsure, I wasn't positive if the charge distribution was moved due to the movement or just by being place inside another uncharged object.

 

[sophiecentaur]

I imagine that there could be a certain degree of polarisation of the sphere due to the acceleration. But you would need to specify what actually happens to cause the acceleration. Contact with the floor of the elevator would be providing the accelerating force which would be distorting the sphere . You can't have any 'ideal' situations when you are looking this deep into the situation so you would have to include the disturbance of charges due to mechanical strain of the sphere.

 

[BvU]

So which is it ?

sphere or cylinder that accelerated upward or downward

by being place inside another uncharged object

I still don't see what is so clear to you ...

 

[sophiecentaur]

But you would need to specify what actually happens to cause the acceleration.

I am bumping this question @almost20characters because you need to describe your experiment more fully before you can predict a result.
A mechanical force implies added Electric Forces. A gravitational force (uniform Field) would accelerate everything the same so no relative displacement of charges.

 

[tech99]

A gravitational force (uniform Field) would accelerate everything the same so no relative displacement of charges.

This seems ludicrously theoretical, so please shoot me down! If the sphere is charged and in free space and is allowed to accelerate by gravity, then as far as I can see the radial electric field lines will be swept back, as per the Larmor radiation mechanism. This will cause charges to be slowly dragged towards the trailing side of the sphere. In doing so they will constitute a current, and the trailing side will acquire more charges than the leading side, so a potential difference will exist across the sphere.
Energy will be radiated from the sphere, so it will accelerate less than g. The radiation will, however, be very small, because the wavelength will correspond to the duration of the fall, and the distance traveled will be very small compared to this wavelength.
When the sphere stops, charges will return to equilibrium and as they do so, more radiation will occur as the charges bounce back and forth a few times due to the resonance of the sphere.

 

[BvU]

Elevators don't accelerate so fast ...

 

[BvU]

The specific scenario given was a sphere with uniform charge density is placed in an elevator, so I suppose the charge distribution would change if the sphere was a conductor? so then the charge would be on the outer surface of the sphere. This is why I was unsure, I wasn't positive if the charge distribution was moved due to the movement or just by being place inside another uncharged object.

Let's move this to homework and use the template there: a full problem description is very helpful.

 

[berkeman]

Specifically, if I had a sphere or cylinder that accelerated upward or downward, it's clear that the distribution of charge, rho, would shift. However would the density turn into some function of increasing rho as the radius increases? I assumed that the density of charge would basically turn into a blob and I'd need to integrate the non uniform surface of charge then, but I'm making a lot of assumptions I'm not confident with. Would appreciate any help!

The specific scenario given was a sphere with uniform charge density is placed in an elevator, so I suppose the charge distribution would change if the sphere was a conductor? so then the charge would be on the outer surface of the sphere. This is why I was unsure, I wasn't positive if the charge distribution was moved due to the movement or just by being place inside another uncharged object.

Let's move this to homework and use the template there: a full problem description is very helpful.

At the moment, the Mentors are unsure whether to move this to the Homework Help forums. But we are unanimous that the OP needs to show a lot more effort in this thread.

@atmost20characters -- Please show us what Relevant Equations you think would apply to this type of problem, and try putting in some numbers to see if you can calculate whether there is any appreciable charge density change with acceleration...