The diagram shows the arrangement of three small unifromly charged spheres A, B and C. The arrows indicate the direction of the electrostatic force acting between the spheres (for example, the left arrow on sphere A indicates the electrostatic force on shphere A due to sphere B). At least two of the spheres are positively charged. Which sphere, if any, could be negatively charged?

Options

A. sphere A
B. sphere B
C. sphere C
D. no sphere

Answer

A

Explanation

It can be seen from the diagram that only the sphere B and C repel. Hence they both must e of same type. According to the fact that at least two spheres are positively charged, therefore both spheres should be positively charged. Since attraction occurs for two remaining pairs it can be concluded that the sphere A is negatively charged.