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blue_lilly
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Homework Statement
The figure below shows two parallel plates. Assume they are infinite in area (this way we can neglect edge effects). The plate on the left is at a potential of +60V and the plate on the right is at a potential of 0V. The plates are a distance 20cm apart and the dashed lines are spaced equally 5cm apart.
https://www.physicsforums.com/attachments/66183
*If the image doesn't work there is a positive plate on the left and a negative plate on the right. The distance between the 2 plates is 20cm. Point C is located 15 cm from the left plate and 5 cm from the right plate.*
What is the magnitude of the electric field at point C?
Homework Equations
ΔV= - E * d * cosθ
E = - (ΔV) / ( d * cosθ )
The Attempt at a Solution
I know ΔV=60 and cosθ= cos(0)= 1. I am given d=20 cm between the two plates.
At first I was using d= 0.2, [E=-(60)/(.2*1)=300 N/C] but that answer is wrong, i think because the d=.2 value is for the whole system and not "Point C".
So I thought that I should be using a d value that corresponds with the "Point C".
What i am confused about is "Point C" is located at either the 5 cm or the 15 cm mark, depending which direction you are going. So it could either be...
E = - (60) / ( .15 * 1 ) = 400 N/C
or
E = - (60) / ( .05 * 1 ) = 1200 N/C
However the website says both of these are wrong and I am not really sure why.
Any help would be GREATLY appreciated!