/sci/ - Science & Math » Thread #11786204

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Can i get some help from plase?

Anonymous Thu 11 Jun 15:48:31 2020 No.11786204 View Reply Original Report

Quoted By: >>11786211 >>11786252 >>11786410

Anonymous

Anonymous Thu 11 Jun 2020 15:52:47 No.11786211 Report

Quoted By:

>>11786204
Who's Plase? Maybe you should ask him?

Anonymous

Anonymous Thu 11 Jun 2020 15:55:54 No.11786220 Report

Quoted By:

you shall not trust 4chan for help, how innocent I am

Anonymous

Anonymous Thu 11 Jun 2020 16:06:17 No.11786252 Report

Quoted By: >>11786305 >>11786888

>>11786204
I will use vector arrows instead of shitty bold letters.

(a)
Using the chain rule:
$\vec E = - \vec \nabla V = \frac{A}{r^2} \vec \nabla r = \frac{A}{r^2} \frac{2 \vec r}{2 r} = \frac{A \vec r}{r^3}$

Anonymous

Anonymous Thu 11 Jun 2020 16:23:22 No.11786305 Report

Quoted By: >>11786336

>>11786252
(b)
$ \rho = \varepsilon_0 \vec \nabla \cdot \vec E = \varepsilon_0 \left( \frac{3 A}{r^3} + \frac{-3 A \vec r}{r^4} \cdot \left( \frac{-2 \vec r}{2r} \right) \right) = 0 $
This means it's the field of a point charge.

Anonymous

Anonymous Thu 11 Jun 2020 16:31:39 No.11786336 Report

Quoted By: >>11786402

>>11786305
(c)
Integrate over a sphere with radius R and use rotational symmetry.
$ Q = \varepsilon_0 \oint \vec E \cdot d\vec A = \varepsilon_0 \frac{A}{R^2} 4 \pi R^2 = 4 \pi \varepsilon_0 A $

Anonymous

Anonymous Thu 11 Jun 2020 16:47:48 No.11786402 Report

Quoted By:

>>11786336
(d)
Same shit as in (c). If the sphere is big enough then the field lines will still hit the sphere approximately orthogonal.

$ \oint \vec E \cdot d\vec A = \frac{Q}{\varepsilon_0} \\ E(r) 4 \pi r^2 = \frac{S \sigma}{\varepsilon_0} \\ E(r) = \frac{S \sigma}{4 \pi \varepsilon_0 r^2} \\ V(r) = \frac{S \sigma}{4 \pi \varepsilon_0 r} $

Anonymous

Anonymous Thu 11 Jun 2020 16:50:36 No.11786410 Report

Quoted By:

>>11786204
Are you going to post your entire from home exam, or just give us bits and pieces?
Besides, your professor is going to catch you.

Anonymous

Anonymous Thu 11 Jun 2020 19:45:43 No.11786888 Report

Quoted By:

>>11786252
>I will use vector arrows instead of shitty bold letters.
Nicely said, the real crime here is how masochistic your prof is in his/her application of notation

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