A negatively charged rod is brought near (without touching) a neutral metal sphere on an insulating stand. No grounding occurs. Which statement best describes the sphere's final net charge after the rod is removed?
- It is negative because electrons are pulled onto the sphere from the rod through the air gap.
- It is positive because electrons are pushed off the sphere and lost to the surroundings.
- It is zero because charges only separate temporarily and then recombine, conserving net charge. (correct answer)
- It is zero because a neutral object contains no charges that can be rearranged.
Explanation: This question tests conservation of electric charge and charging. When a charged rod is brought near a neutral conductor without touching or grounding, it only causes temporary charge separation (polarization) within the conductor—electrons move to one side, leaving positive charge on the other. However, the total number of electrons and protons in the sphere remains unchanged, so the net charge stays zero. When the rod is removed, the separated charges recombine, returning the sphere to its original neutral state with zero net charge. Choice A incorrectly suggests electrons can jump through air—at typical voltages, air is an insulator preventing charge transfer without contact. For polarization without grounding: charge separates temporarily but net charge always remains unchanged.