[ 3 / biz / cgl / ck / diy / fa / ic / jp / lit / sci / vr / vt ] [ index / top / reports ] [ become a patron ] [ status ]
2023-11: Warosu is now out of extended maintenance.

/sci/ - Science & Math

View post   
File: 3 KB, 428x235, 01049.png [View same] [iqdb] [saucenao] [google]
6386338 No.6386338[DELETED]  [Reply] [Original]

/sci/,

I have a little problem with the forces and fields that generate electricity. I want to describe to you what I think happens so you can correct me.

Let's start with a charged capacitor, just two plates close to each other, separated by an insulator on one side, and connected by a wire from the other. One of the plates will have an excess of electrons, the other -- lack. The lack of electrons on one of the plates (+) creates an electric field which spreads through the wire to the other plate. The electrons inside the wire and on the other plate will start moving toward the source of the field, until there are enough electrons on the (+) plate. How does voltage come into play if the above is correct? It clearly isn't needed to describe the cause of electron current..

>> No.6386359

The thing you seem to be forgetting is that there is a voltage on the cap if it has any charge on it. The voltage will be the integral of the electric field over distance. The electric field is going to depend on the charge density and the dielectric constant of the material.

If they're connected by a wire, they'd just discharge (which is what I assume you're describing) until the charge is zero.

>> No.6386360

>>6386359
/thread

>> No.6386361

>>6386359
Yep, that was what I was missing -- how is the electric field related to voltage. Thanks.

>> No.6386649

>>6386361

Field is integral of charge density. For plates, you consider charge density a delta function in the plates, and charge density of zero between the plates.

Electric field between the plates then is integral of charge density, which evaluates to Q/(A*epsilon).

Voltage is integral of electric field over distance. Since the electric field is a constant, V = E * d (separation) = Q/(A*epsilon)

>> No.6386653

> separated by a dielectric
ftfy