The diagram shows the arrangement of three small uniformally charged spheres, `A,B` and `C`. The arrow indicate the direction of the electrostatic forces acting between the spheres (for example, the left arrow on sphere `A` indicates the electronstatic force on sphere `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.