What does it mean to be electrically neutral?

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What does it mean to be electrically neutral?

Postby Natural ChemE on May 2nd, 2010, 6:05 pm 

After this is done, the shell is electrically neutral.


I realize that this is horrible, but I've honestly blanked on the definition of "electrically neutral" in the context of Physics. I'm blaming the sleep deprivation and that pink elephant dancing in the corner of the room - that bastard's supposed to remember this stuff for me. Also, he was green yesterday which just raises more questions than I'm prepared to deal with at this moment.

-If a shell is electrically neutral, does this mean it lacks a charge? Or an electrostatic potential? Or a non-zero electric field? Or what?

Incase it's relevant, this is the context of Laplace's Equation. The answer to this question is going to set a boundary condition at the surface of the shell, but I'm not sure what that boundary condition is since I can't recall what the term means.
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Re: What does it mean to be electrically neutral?

Postby Lincoln on May 3rd, 2010, 10:55 am 

To be electrically neutral means no net electrical charge.

You could have a point shell surrounded by a shell of some kind. While there might be some sort of electrical field configuration induced, if the shell is neutral, it means that it has identical numbers of positive and negative charges.
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Re: What does it mean to be electrically neutral?

Postby ailker on May 9th, 2010, 2:14 pm 

in fact there are equal amount of positive and negative charges. This means that it is electrically neutral. There are always charges but there can be changes about the amount of them. For example if it loses one electron there will be an excess of positive charges in other words it is positively charged.
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Re: What does it mean to be electrically neutral?

Postby Natural ChemE on May 10th, 2010, 1:28 am 

Thanks for the help!

At the time, I was stressing out and concerned that there might be an additional connotation behind "electrically neutral" - i.e., equipotential throughout the body or something.

Which is still kinda confusing me. The overall object didn't bear a net charge, but since it was a conductor in an external electric field, most of the individual sections of it did bear a net charge.

It feels like having a stick which has one half frozen and the other half on fire, then saying the stick’s at room temperature because the volume-averaged heat content of the stick would be at room temperature if the heat content was evenly distributed throughout the stick.
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Re: What does it mean to be electrically neutral?

Postby Lincoln on May 10th, 2010, 7:11 am 

In the equations, it just means you shouldn't have any source term. It's an "all boundary condition" problem.
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