A positively charged rod is brought close to an uncharged metal sphere standing on an insulating stand, without touching it. What is the net charge on the sphere while the rod is held near it?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Zero; the sphere remains electrically neutral
A body gets a net charge only when charge is added to it or removed from it. The sphere stands on an insulating stand and the rod never touches it, so no charge can reach it or leave it. The field of the rod only moves the free electrons of the metal towards the side nearer the rod. So the charge already in the sphere is redistributed. By conservation of charge, its total stays zero.
Option (1) Positive — Incorrect. The sphere would be positive only if it lost electrons. With no contact and an insulating stand, no electrons can leave it.
Option (2) Negative — Incorrect. The side nearer the rod does become negative. But the far side is left with an equal positive charge, and the two add up to zero.
Option (3) Zero; the sphere remains electrically neutral — Correct. The charges on the near and far sides are equal and opposite. So the sphere as a whole stays neutral as long as no charge is transferred to or from it.
Option (4) It depends on the distance of the rod — Incorrect. Bringing the rod nearer separates more charge within the sphere. But the separated charges stay equal and opposite, so the net charge is zero at every distance.
NCERT (2026-27):
Electric Charge – “To electrify a neutral body, we need to add or remove one kind of charge. When we say that a body is charged, we always refer to this excess charge or deficit of charge.”
Charge is Conserved – “… Within an isolated system consisting of many charged bodies, due to interactions among the bodies, charges may get redistributed but it is found that the total charge of the isolated system is always conserved.”