[Electromagnetics] E-Fields & Equipotential Surfaces

[lonelypancreas]

Homework Statement

This is from the book Engineering Electromagnetics by Hayt & Buck.[/B]

Homework Equations

E = - (ΔV/ΔL)[/B]

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.[/B]

Were there things that I have overlooked?

 

[kuruman]

Were there things that I have overlooked?

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.

 

[lonelypancreas]

You overlooked that the 102 V equipotential is closer than 2 mm to the 104 V equipotential.

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?

 

[andrevdh]

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