question_answer

In a certain charge distribution, all points having zero potential can be joined by a circle an S. Points inside S have positive potential points outside S have negative potential. A positive charge, which is free to move, is placed inside S:

A)  it will remain in equilibrium

B)  it can move inside S, but it cannot cross S

C)  it must cross S at some time

D)  it may move, but will ultimately return to its starting point