# Homework Help: [Electromagnetics] E-Fields & Equipotential Surfaces

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1. Apr 2, 2017

### lonelypancreas

1. The problem statement, all variables and given/known data
This is from the book Engineering Electromagnetics by Hayt & Buck.

2. Relevant equations
E = - (ΔV/ΔL)

3. The attempt at a solution
At part (a), I took the potential difference between point A and the point directly above at the higher surface (106 V) and plugged in the needed values:
E = - (106-104 V)/(2-Ay mm) = - 1000 V/m which is ≠ -1075-Ay V/m.

Were there things that I have overlooked?

2. Apr 2, 2017

### kuruman

You overlooked that the 102 V equipotential is closer than 2 mm to the 104 V equipotential. You will get a higher magnitude for E if you take that into account.

3. Apr 2, 2017

### lonelypancreas

I think I'm kinda lost.
So do I have to include the potentials from point A with respect to ALL equipotential surfaces? (i.e. 106-104 V, 108-104 V, etc.)? And with respect to the 102-V surface, is the coordinate of the point below point A relevant? If so, how do I get its coordinate?

4. Apr 3, 2017

### andrevdh

Your calculation give an average value somewhere between the two ep lines considered.
Maybe drawing an V(y) graph will make it clearer?

Last edited: Apr 3, 2017