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## #1 2010-04-11 20:52:30

psychist101
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### physics formula, dont understand the maths

hello

this is gauss law for electricity, but what do all the symbols mean? what i would realy like it an example calculation, so that i can see how exactly it works. i'm more of a physics guy not a maths guy

thx

psychist101
Guest

bumpp

psychist101
Guest

????????

## #4 2010-04-17 08:28:54

G_Einstein
Member
Registered: 2008-08-30
Posts: 124

### Re: physics formula, dont understand the maths

it is

E is the electric field,which is inependent in this case so

dA=area
if you ahve just one elecric load it is just q
so

If you have a sfear,the area is

so

just

Last edited by G_Einstein (2010-04-17 08:29:39)

Se Zoti vete e tha me goje,se kombet shuhen permbi dhe,por SHqiperia do te roje,per te,per te luftojme ne.
God said that all nation exincts on the ground,but Albania will survive,for it,for it we are fighting.

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## #5 2010-04-17 08:35:30

G_Einstein
Member
Registered: 2008-08-30
Posts: 124

### Re: physics formula, dont understand the maths

E is the elctric field,the very elementary piece of the surface that you inegrate,pesilon mean the electric features of the meidum where is the area and q is the electrical load

if you have density you have to make

and to continue.

Do you want to make a specifi case ?
For sphere or cilinder with density??

Last edited by G_Einstein (2010-04-17 08:35:51)

Se Zoti vete e tha me goje,se kombet shuhen permbi dhe,por SHqiperia do te roje,per te,per te luftojme ne.
God said that all nation exincts on the ground,but Albania will survive,for it,for it we are fighting.

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## #6 2010-04-17 11:07:13

Identity
Member
Registered: 2007-04-18
Posts: 934

### Re: physics formula, dont understand the maths

If you have a closed surface, at each point on the surface you take the dot product of

and
and add them up. This will equal the charge contained inside the surface divided by epsilon nought.

The symbol

just means a surface integral of a closed surface.

In general, for the surface

The surface integral of the vector field

is

Where the RHS is a simple area integral. Note that different orders of the cross product will give different answers. This is because each surface has two orientations (two surface area vectors pointing out from every point on the surface).

This allows you to compute a surface integral.

If you want examples see http://tutorial.math.lamar.edu/Classes/ … grals.aspx

The differential form is derived through an application of Stoke's theorem.

If

This is called the divergence of the vector field.

It's easy enough to compute examples in the differential form.

Last edited by Identity (2010-04-17 11:12:03)

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