Physics · Electric Charges And Fields · NEET
In conduction the charged body TOUCHES the neutral body, so charge actually flows across and both end up with the SAME sign of charge. In induction there is NO touching: the charged body is only brought near, which pushes the neutral body's electrons to one side. The near side gets the OPPOSITE charge and the far side gets the same charge. If you never earth it, the body is still neutral overall once you take the rod away.
No. Induction happens without contact. You bring a charged rod near a conductor, the free electrons rearrange, and one side becomes oppositely charged. To make the charge stay, you earth (ground) the far side while the rod is still near, then remove the earth, then remove the rod. The body is left with a permanent charge OPPOSITE to the rod. This is why induction gives opposite sign, just like friction.
This is induction at work. The charged rod pulls the opposite charges of the neutral paper to the near side and pushes the like charges to the far side. Because the opposite charge is now CLOSER, the attractive force is stronger than the repulsion from the far side. Net result: attraction. This is a very common NEET/board conceptual question.
By convention, glass rubbed with silk becomes POSITIVE (it loses electrons to the silk), and the silk becomes negative. A plastic rod rubbed with fur becomes NEGATIVE (it gains electrons). NCERT fixes these conventions, so memorise: glass+silk = glass positive; plastic+fur = plastic negative. Only electrons transfer; charge is conserved, so the two bodies get equal and opposite charge.
Only if you earth it during the process. If you just bring a rod near a conductor and take it away without earthing, the electrons return to their original spots and the body is neutral again. To trap a permanent charge you must earth the far side while the rod is near, break the earth connection first, then remove the rod. Then the induced OPPOSITE charge stays for good.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Only electrons move. Protons are fixed in the nucleus. A body becomes negative by GAINING electrons and positive by LOSING electrons. This is true for friction, conduction and induction alike.
No. Charge is conserved. Rubbing only transfers electrons from one body to the other. What one body gains, the other loses, so the total charge stays the same (usually zero for two neutral bodies).
Induction works best on conductors because they have free electrons that can move to one side. In insulators only slight polarisation of molecules happens, which is why a charged rod can still weakly attract paper, but you cannot store a large induced charge on an insulator.
Yes, once you earth it. Earthing lets electrons flow in or out to ground, so the body ends up with a net charge opposite to the inducing rod. Without earthing, the total charge stays zero.
The induced charge can at most equal the inducing charge in magnitude (for a fully surrounding conductor). For a normal nearby body only part of the charge is induced, so the induced charge is generally smaller than the charge on the rod.
