# Why is the Answer C? Electric Field in Conductors

• SmartAries
In summary, the conversation discusses the net electric field at a point inside a conductor, which will be zero, but the field due to the charge on the surface of the sheet will not be zero. The conversation also touches on how to determine the direction of the field without knowing the sign of the charge, and raises concerns about the reliability of multiple choice answers.
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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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.

TSny said:
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?

SmartAries said:
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
SmartAries said:
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.”

## 1. Why is the answer C when discussing electric field in conductors?

The answer C is typically the correct answer when discussing electric field in conductors because it refers to the charge density on the surface of the conductor. In other words, the electric field inside a conductor is zero, but the electric field on the surface of a conductor is determined by the charge density.

## 2. How does the electric field inside a conductor differ from the electric field outside a conductor?

The electric field inside a conductor is zero, while the electric field outside a conductor is determined by the charge density and shape of the conductor. This is due to the fact that charges inside a conductor will rearrange themselves in such a way that the electric field inside the conductor is canceled out.

## 3. Can the shape of a conductor affect the electric field inside it?

Yes, the shape of a conductor can affect the electric field inside it. The electric field inside a conductor is determined by the charge density, and the shape of the conductor can affect how the charges are distributed on the surface of the conductor, thus affecting the electric field inside.

## 4. How does the presence of a charge inside a conductor affect the electric field inside?

If a charge is placed inside a conductor, the charges on the surface of the conductor will redistribute themselves in order to cancel out the electric field inside the conductor. This is known as the Faraday cage effect.

## 5. How does the electric field inside a conductor relate to the potential inside?

The electric field inside a conductor is directly related to the potential inside. In fact, the potential inside a conductor is constant, and the electric field is zero. This is because the charges inside a conductor will always rearrange themselves in such a way that the potential inside remains constant.

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