# Electric Field Problem -- A charged particle outside of an infinite conducting sheet

SmartAries
Homework Statement:
A particle with charge Q is placed outside a large neutral conducting sheet. At any point in the interior of the sheet, the electric field produced by charges on the surface is directed:

A. toward the surface
B. away from the surface
C. toward Q
D. away from Q
E. none of the above
Relevant Equations:
(Conceptual)
The answer according to the key is C. I thought the answer would be E since the electric field inside a conductor is always zero. Can someone explain why the answer is C?

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Homework Helper
Gold Member
The net electric field at a point P inside the conductor will be zero. But, the field due to the charge on the surface of the sheet will not be zero at P.

SmartAries
The net electric field at a point P inside the conductor will be zero. But, the field due to the charge on the surface of the sheet will not be zero at P.

Ah, I see. How do we get an indication of the direction of the field if we are not given the sign of charge Q?

Homework Helper
Gold Member
How do we get an indication of the direction of the field if we are not given the sign of charge Q?
Good question. Without knowing the sign of Q there is not a definite answer to the question.
If I had to make a choice, I would assume Q is positive.

PhDeezNutz
Cutter Ketch
Ah, I see. How do we get an indication of the direction of the field if we are not given the sign of charge Q?

Criminal. The correct answers for both signs are among the multiple choice answers. Getting a correct answer should not depend on you reading the professor’s mind correctly. Complain vociferously and don’t let him/her weasel out with some lame excuse like “Well, obviously if I don’t state the sign it’s positive.”