# Homework Help: Electric field near metal plate

1. Jan 26, 2010

### Keano16

1. The problem statement, all variables and given/known data

An infinite, thin, uniformly charged rod (line charge density lambda) is placed parallel to a metal plate a distance d above it. Calculate the E-field close to the surface of the plate as a function of perpendicular distance to the rod.

2. Relevant equations

3. The attempt at a solution

I calculated that at a perpendicular distance d away, the E-field of an infinite rod would be (lambda)/(2*pi*epsilon*d). I also realise that the method of images needs to be applied in this case in order calculate the charge induced onto the plate, and that would require me to consider an identical infinite rod at -d from the plate, with a line charge density of -lambda. However, I do not know how to proceed from here, as calculating the total potential keeps giving me 0.

Thanks

2. Jan 26, 2010

### ideasrule

So if there's a negatively charged rod 2d from a positively charged rod, what's the electric field in their middle?