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 sphere C repel. Hence they both must be 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.