# Homework Help: Direction of electrostatic force and field?

1. May 31, 2010

### MCATPhys

In a pith-ball electroscope, a ball made of pith, which is a light-weight electrical insulator, is suspended from a hook via a silk thread. When the electroscope is placed in the vicinity of a negatively charged object on the right, the ball moves towards the object. What is the direction of the electric field?

It should be to the right... because then the force on the negatively charged object would be pointing left... am i right?

2. May 31, 2010

### MCATPhys

but the right answer is left... "because the charged object will attract the pith ball, the force must be pointing to the right; that means the electric field points to the left"

is the book wrong?

3. May 31, 2010

### RoyalCat

Puzzling, the negatively charged object would induce a small positive charge on the pith ball. As such, since the force on it is to the right, the field resulting the force must also point to the right (E field goes out from positive charges, and in to negative ones).

Maybe the book phrased the layout of the system poorly? Or it could just be a mistake, unless we're both missing something.