A student is investigating what happens when a neutral metal sphere sitting on an insulated stand is touched by a negatively charged rod. The set up for the student's investigation is shown in the diagram. What will happen to the excess electrons when the negatively charged rod touches the metal sphere?

Question

A. The excess electrons will move from the sphere to the rod and spread out along the rod.
B. The excess electrons will move from the rod to the sphere and spread out on the sphere.
C. The excess electrons will move from the rod to the sphere and stay clustered in the area where the rod touches the sphere.
D. The excess electrons will move from the sphere to the rod and stay clustered near the end of the rod that touches the sphere.

Answer 1

When a negatively charged rod touches a neutral metal sphere, electrons will move due to the potential difference between the charged rod and the neutral sphere. The negatively charged rod has excess electrons, and since the sphere is neutral, it has an equal number of protons and electrons.

Upon contact, the excess electrons from the negatively charged rod will move to the neutral sphere, because like charges repel and the sphere will attempt to balance out the charge. Electrons will spread out across the surface of the sphere since it is conductive and allows charge to distribute evenly.

Given the options provided, the correct answer is:

B. The excess electrons will move from the rod to the sphere and spread out on the sphere.