Calculating Charge & Electric Energy Above a Plane

In summary, the conversation discusses the use of the method of images to determine the total charge and stored electric energy of an infinite conducting plane with a charge above it. The result indicates that the capacitance of the system would be negative, which is not possible. The individual is seeking confirmation of their understanding.
  • #1
bg646
1
0
Hello, I am stuck with this one. Your help/comments would be most appreciated.

A charge "+Q" lies at a distance "d" above an infinitely large conducting plane. Applying the method of images, i found the right result that the total charge of the infinite plane is "-Q" and that the stored electric energy is:
[tex]W_{E}=-\frac{Q^{2}}{8\pi\epsilon_{0}d}[/tex]
Since the stored electrostatic energy also satisfies:
[tex]W_{E}=CV^{2}/2[/tex]

it seems that the capacitance of the system would be negative which must be non sense. Therefore the charge above the plane is *not* a capacitor.

Is this correct or am i missing something?
Thanks for your help
 
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  • #2
And the question was ... ?
 

1. What is the formula for calculating electric charge above a plane?

The formula for calculating electric charge above a plane is q = σA, where q is the total charge, σ is the surface charge density, and A is the surface area.

2. How do you calculate the electric field above a plane?

The electric field above a plane can be calculated using the formula E = σ/2ε0, where E is the electric field, σ is the surface charge density, and ε0 is the permittivity of free space.

3. What is the unit of measurement for electric charge?

The unit of measurement for electric charge is the Coulomb (C).

4. How does the distance from the plane affect the electric field?

The electric field above a plane decreases as the distance from the plane increases. This relationship follows an inverse square law, meaning that the electric field is inversely proportional to the square of the distance from the plane.

5. Can the electric field above a plane ever be zero?

Yes, the electric field above a plane can be zero if the surface charge density is also zero. In this case, there is no net charge above the plane and therefore no electric field.

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