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Robin Lee
- 10
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1. Positive and negative charges are distributed evenly in two parallel plates with width "w". The density of the positive and negative charge is +[tex]\rho[/tex] and -[tex]\rho[/tex]. Assume that the length of the plates at y direction is [tex]\infty[/tex]
(a) Find the electric field in the plates
(b) Let the electric potential at x=-w equal to 0, find the electric potential in the plates.
Homework Equations
[tex]\Delta[/tex]E=k*Delta-Q*r/r2 where r is the unit vector -- (1)
3. My approach
I sliced an infinitesimal portion of the plate horizontally denoted as Delta-y and represent the charge Delta-Q = rho *Delta-y*2*w. Is my expression for Delta-Q correct?
r is the observation point which is at opposite to the portion Delta-y on the negative plate of which magnitude is "w".
Substitute my expression for Delta-Q into (1), I obtain Delta-E = k*rho/w.
Do I have to integrate Delta-E from -infinity to +infinity to obtain the electric field in the plates? If so, I will get E=0. Does this make sense?
Thank you.
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