# The Naked Scientists Forum

### Author Topic: Electromagnetism Questions  (Read 2863 times)

#### Supercryptid

• Hero Member
• Posts: 606
##### Electromagnetism Questions
« on: 23/05/2005 01:13:50 »
Do electrically-charged objects have an "electromagnetic escape velocity"? Here's an example for clarification of my question:

Imagine a gigantic, negatively charged sphere, about the size of Earth. There is a positively charged rocket resting on the surface of this sphere. The strength of electromagnetic attraction between the giant sphere and the rocket is equal to 1 G (assume here that gravity is irrelevant). That 1 G of force results from the electrical attraction between the rocket and the sphere, not gravity. For all intents and purposes, this has the same effect as an uncharged rocket sitting on Earth, where gravity produces 1 G instead of electromagnetism, correct?

Now, let's assume that this rocket wants to take-off of the sphere and get into space. Since the strength of electrical attraction is 1 G, just like on Earth, does the rocket have to attain a certain "escape velocity" to get into space and escape the electromagnetic field? Would it be the same as the Earth's gravitational escape velocity  of about 25,000 mph?

From this idea, I was wondering if there might be an electromagnetic analog of a blackhole. Just as a blackhole has so much gravity that any object with mass cannot escape from it, even by going light-speed, might there also be an object that has so much electrical charge that no electrically-charged object can escape from its pull, even by going light-speed? The situation would be reversed for objects that have the same charge as this "Massively-Charged Object" (MCO), in which the resultant repulsion is so great that they could not approach it even at light-speed.

I'm not exactly sure how to make an MCO, since squishing large numbers of electrically-charged particles together into a blackhole-like density would be strongly opposed by repulsion.

Could an MCO exist, theoretically speaking?

#### realmswalker

• Sr. Member
• Posts: 205
##### Re: Electromagnetism Questions
« Reply #1 on: 23/05/2005 06:03:14 »
hmmm
if in a higher dimension that has different spatial properties than ours where you could create 2 spheres of similarly charged particles so that neither one was on the outside but both were inside of the other (this is possible i believe in some dimension, ive seen those models and stuff) then you could do it.

#### daveshorts

• Moderator
• Neilep Level Member
• Posts: 2583
• Physics, Experiments
##### Re: Electromagnetism Questions
« Reply #2 on: 23/05/2005 13:37:33 »
Yes there would be an escape velocity, and if the sphere was the same size as the earth (and was massless) the escape velocity would be the same (if the sphere was non-conducting as otherwise you would get strange effects where the charge distribution on the earth would be altered by the rocket)

I haven't heard of a electromagnetic analog of a black hole... I don't think that light is affected by very strong electric fields - although it is the sort of thing I could imagine would happen and is possibly known about but talked about in very different terms. Possibly as a non-linearity of a vacuum - does anyone else know any more about this?

#### gsmollin

• Hero Member
• Posts: 749
##### Re: Electromagnetism Questions
« Reply #3 on: 23/05/2005 16:22:36 »
Yes, there would be an escape velocity, because the electric charge has an inverse-square-law force field, similar to gravity. I believe there could be a theoretical arrangement where the two charges are pulled together with a force large enough to have an escape velocity of c. However, we do not observe such powerful charges, because there are two kinds of charge, and such a dipole would attract neutralizing charges. I also suspect the vacuum could produce neutralizing charges as the two highly charged objects are separated, since a lot of energy would be expended to separate the charges.

#### qazibasit

• Sr. Member
• Posts: 344
##### Re: Electromagnetism Questions
« Reply #4 on: 23/05/2005 17:45:15 »
well ya your approach is too good but well i was wondering the same thing that if there a medium in space as was previously believed like ether then what would be the effect of black hole on sound wave having a very low velocity than light. i believe that it would have escaped through it coz gravity has effects on particle nature things and wave are not particle nature whereas light has both properties.

#### The Naked Scientists Forum

##### Re: Electromagnetism Questions
« Reply #4 on: 23/05/2005 17:45:15 »