(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Charge is distributed uniformly on the surface of a large flat plate. The electric field 2cm from the plate is 30 N/C. The electric field 4cm from the plate is:

A. 120 N/C

B. 80 N/C

C. 30 N/C

D. 15 N/C

E. 7.5 N/C

2. Relevant equations

E=kq/r^2 (possibly)

3. The attempt at a solution

Well, the answer I got was E, 7.5 N/C. I got that by using the above equation, plugging in 30 for E and 2 for r and solving for q. Then, I used that same value of q and the new r to solve for E and got 7.5 N/C. Supposedly the correct answer is C, 30 N/C. I don't understand how they got that though. Why is the E field still the same? Shouldn't it be decreasing with the greater distance?

Anyways, I think I might be wrong because I remembered afterwards that E=kq/r^2 is the E field due to a point charge and not a plate....maybe that's why I got the wrong answer?

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# Homework Help: Electric Field (multi choice)

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