When charge on a conductor is in equilibrium, the field lines are excluded from the bulk of the conductor and the field lines are perpendicular to the surface. The picture shows a magnified view of one part of a conductor, with electrons at the surface and no field lines inside. This is not equilibrium, however, because the field lines are not perpendicular. How will the electrons move in response to this field?

1. They won't move
2. They will move to the right
3. They will move to the left
4. They will move in the direction of the field lines
5. They will move opposite to the direction of the field lines

Because F = qE, and electrons have a negative charge, they feel a force opposite to the field. They're already at the surface of the conductor, though, and unless the field is very large they'll stay on the conductor. The force has a component to the left so the electrons move left, carrying the field lines with them. The electrons stop moving when the field lines are perpendicular to the surface.