Electro Mag. basic (very basic :P) question check

[Sarahisme]

hey just wanted to check if my answer for the following question is correct...

 

Thanks

Sarah

[swansont]

What's there looks good, but you should specify exactly how the charges are distributed - it's unclear if you mean that the charges are unformly distributed throughout the volume or on the surface.

[Sarahisme]

oh ok, well i am not 100% sure on that but i assume that the charges would be uniformly distributed throughout the volume?

[5614]

Isn't it the surface???

 

(similar to a van de graff generator?)

 

Also don't charges tend to accumulate on the surface in general?

[swansont]

oh ok, well i am not 100% sure on that but i assume that the charges would be uniformly distributed throughout the volume?

 

But the charges are free to move if it's a conductor, so they tend to repel each other to maximize their separation distance, which minimizes their energy.

 

You can also think of it this way: if there are charges in the interior, there is also an electric field there, which will push the charges outward, which means there can be no charges in the interior when you are in equilibrium. There is also no electric field inside when in equilibrium. All the charge will reside on the surface.

 

Good think I asked, eh? Now you know.

[5614]

Good good and I suppose that's an entirely logical reasoning which only leaves me with one question.

 

High currents:

 

Actually, is higher currents electrons moving faster or more more electrons moving at once?

 

I suppose electrons moving faster due to the high potential energy is logical, as is; due to the high potential energy more electrons will be 'mobilised'.

 

Anyway, if it is more electrons moving then will the outter part become denser in electrons, or will they start to fill up the middle too?

[Sarahisme]

But the charges are free to move if it's a conductor' date=' so they tend to repel each other to maximize their separation distance, which minimizes their energy.

 

You can also think of it this way: if there are charges in the interior, there is also an electric field there, which will push the charges outward, which means there can be no charges in the interior when you are in equilibrium. There is also no electric field inside when in equilibrium. All the charge will reside on the surface.

 

Good think I asked, eh? Now you know. [/quote']

 

 

oh ok yeah that makes sense now that i think about it defenitely a good thing you asked! i learnded somthin haha

 

so my answer for part b) should look more like this...???

[swansont]

oh ok yeah that makes sense now that i think about it defenitely a good thing you asked! i learnded somthin haha

 

so my answer for part b) should look more like this...???

 

Yes. In fact it was the charge in the middle that made me eonder if that was a surface or volume image you were giving. You should mention that the charges are on the surface.

[swansont]

Good good and I suppose that's an entirely logical reasoning which only leaves me with one question.

 

High currents:

 

Actually' date=' is higher currents electrons moving faster or more more electrons moving at once?

 

I suppose electrons moving faster due to the high potential energy is logical, as is; due to the high potential energy more electrons will be 'mobilised'.

 

Anyway, if it is more electrons moving then will the outter part become denser in electrons, or will they start to fill up the middle too?[/quote']

 

More charges, I think. Moving faster also means they bump into things more often. But it also depends on whether the higher current is due to higher voltage or smaller resistance (i.e. it may depend on if it's the same wire or you are comparing different types of wire). I'm not sure how much of the current is due to surface charge and volume charge.

[5614]

More charges, I think. Moving faster also means they bump into things more often.

OK, more charges (why 'charges' as opposed to 'electrons'?) pass a point per unit time... but is that because more electrons are moving or because they're moving faster?

[swansont]

OK, more charges (why 'charges' as opposed to 'electrons'?) pass a point per unit time... but is that because more electrons are moving or because they're moving faster?

 

Not all current is due to electron flow, but in the case of a wire it is.

 

The electrons move faster, though the drift velocity is still small. More here

[5614]

Not all current is due to electron flow[/b'], but in the case of a wire it is.

Please expand...

[swansont]

Please expand...

 

In some semiconductors and ionic solutions you can get positive charges flowing.

[5614]

Do you mean positrons? Or like in electrolysis where you can get a positive charge caused by the positive ions?

[swansont]

Do you mean positrons? Or like in electrolysis where you can get a positive charge caused by the positive ions?

 

Protons/nuclei. Some of it is semantics, as you discuss "holes" flowing, which is really just the absence of an expected electron, in semiconductors. And electrolysis would be an example, or in batteries, where you get positive ions that can contribute to the current.

 

And negative current flow isn't always electrons.

 

edit to add: More