Homework Help: Intro electric field question

1. Jun 25, 2006

dzza

I am just reviewing some E&M because i took the class before I ever thought i had that big of an interest in physics and just memorized formulas, etc. Anyway, this is from a "which of the following statements is true" question.

The true statement is: A positive charge experiences an attractive electrostatic force near a neutral conductor.

The alternatives were that it experiences a repulsive force, no force, ...

How come the true statement is indeed true as opposed to a positive charge experiencing no electrostatic force near a neutral conductor?

2. Jun 26, 2006

Teecher

Charge redistributes itself on the surface of the conductor in response to the presence of the charge. Negative charges are brought close to the positive charge, resulting in a net attraction.

3. Jun 26, 2006

Staff: Mentor

Is that true? I wouldn't have expected that "true statement". That would mean that an isolated charge (like an electron) is attracted to neutral atoms.... I didn't know that was true...

4. Jun 26, 2006

Teecher

There must be a redistribution of charge if the surface of the conductor is to remain an equipotential. This induced polarization results in a potential that goes as 1/r4 (the usual dipole goes as 1/r2, plus an extra 1/r2 to account for the decreasing strength of the induced dipole with distance). This does have an analog in atomic/molecular interactions, often referred to as charge-induced dipole forces.