A charged sphere is suspended on an insulating thread. When a plastic rod with a positive charge is held near the suspended charged sphere, the sphere moves to the position shown below:
State the sign of the charge on the sphere.
Give the reason for your answer.
On the figure, draw an arrow to show the electrostatic force on the sphere.
The positively charged plastic rod is removed and replaced by a plastic rod with a negative charge.
Describe the position that the suspended sphere now takes.
