Question

Math-physics problem about Gauss' Law

http://assets.openstudy.com/updates/attachments/53052cace4b022471a64b0f4-munkeyman1985-1392848082760-gausslaw.pdf

First question please

Answer 1

E = q_enclosed/(A*ε_0)
or
E = kq/r

Answer 2

here we have to apply this form of the Gauss theorem:
\[\Large \Phi \left( {\mathbf{E}} \right) = \frac{Q}{{{\varepsilon _0}}}\]

Answer 3

the flux has to be computed on a sphere whose radius is equal to \(8.1\) cm

Answer 4

not a cylinder?

Answer 5

I think no, since the electric field is generated by a charge on a spherical conductor

Answer 6

2*9ee9(.02^2-.048^2)
--------------------divided by
pi*(.081)^2


but isn't something wrong with that above?

Answer 7

the trial charge has to be placed at point P, outside the spherical shell, so the requested field, has the subsequent \(x-\)component:
\[\Large E = \frac{1}{{4\pi {\varepsilon _0}}}\frac{Q}{{{r^2}}} = 9 \cdot {10^9} \cdot \frac{{\left( {1.4 - 8.1} \right) \cdot {{10}^{ - 6}}}}{{{{\left( {8.1 \cdot {{10}^{ - 2}}} \right)}^2}}} = ...\frac{N}{C}\]

Answer 8

what about the point charges?

Answer 9

it is not necessary to know the magnitude of the trial charge

Answer 10

Isn't the equation
\[9*10^{9}(1.4-8.1)*10^{-6}/(4\pi8.1^{2})\]
?

Answer 11

wait, with epsilon nought in the bottom?