Electric Potential (Charged Plane)

[GDGirl]

Teacher explained the solution- thanks!

[alphysicist]

Hi GDGirl,

1. The problem statement, all variables and given/known data
The electric potential of a very large flat metal plate is Vo = 69 V. It carries a uniform distribution of charge of surface density σ = 0.29 μC/m2. Determine the electric potential V at a distance x = 3.3 cm from the plate. Consider the point at x to be far from the edges, and assume that x is much smaller than the plate dimensions.


2. Relevant equations
V=V0+Ex

I don't believe this is quite right. Remember that when you move away from positive charges the potential decreases. Do you see what it needs to be?


E=σ/ϵ0

This could be true, but not the way I read the problem. The formula you have here would be true if they meant that the plate was thick and that each side had σ = 0.29 μC/m2. However, if they meant that the plate was thin, then you would have for the magnitude of the electric field:


|E| = \frac{\sigma}{2\epsilon_0}


so that might be another problem.