| Objective: |
| To describe Gauss's Law applied to electric fields
- used to find total charge enclosed by a surface given the electric
fields emerging. |
| Steps: |
 |
Consider a charge located at the centre of a sphere.
We wish to relate the electric field emerging from the sphere
to the charge contained. |
| |
|
 |
Split the surface area of the sphere into small
areas. |
| |
|
 |
Find the electric field normal to each area and
multiply this by the area. Add together all such areas until the
surface is completely covered. |
| |
|
 |
Evaluate the total - for a sphere, with a charge
at the centre, this is just a radial electric field at the given
radius multiplied by the surface area of the sphere - giving the
total charge divided by permittivity. We can say that the total
electric flux emerging from the surface equals the charge enclosed. |
| |
|
 |
The surface need not physically exist and it need
not be spherical. |