IF WE RUB A RULLER AND TAKE CLOSE TO THE BITS OF PAPER THEY ARE ATTRACTED AND THEN THEY STICK TO RULLER AND THEN FLY AWAY , WHY DO THEY FLY AWAY ? AS PLASTIC IS AN INSULATOR THE ELECTRONS WILL NOT FLOW FROM RULLER TO PAPER NITHER EATHING IS A REASON HERE SO WHERE DOES THE ELECTRON GO PLEASE
GIVE A DEEP EXPLANATION
Answers
Answer:
A plastic ruler rubbed with hair will acquire a net negative electrical charge.
A piece of paper is made of molecules, and each molecule is electrically neutral, but that doesn’t mean that it lacks electrical charges. Molecules have positively charged nuclei and negatively charged electron clouds. On average the positive and negative charges cancel in terms of electrical effects over distances that are easily observable. But this changes when anything with a net electrical charge is brought close to a piece of paper.
Very quickly the net negative charge in the ruler will electrically repel the electron clouds in the paper and attract the nuclei. This will not move electrons completely away from the nuclei of any molecule, but it will slightly shift the average position of all electron clouds away from the ruler and shift the nuclei toward the ruler to a much smaller extent.
Now every molecule in the piece of paper is electrically polarized. The shifting works like the following pattern, but not quite this extreme:
-+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+ -+
I’ve done this with a physical separation to illustrate different molecules, but it really work more like the following:
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Notice that one end (side of piece of paper) is negative and the other end is positive. The charges in between essentially cancel.
The negatively charged ruler is closer to the positive side of the paper and farther from the negative side. There is an attraction between ruler than the positive side and a repulsion between ruler and the negative side. Attraction wins because electrical forces decrease over distance.
If the paper is replaced by a piece of metal the difference is that with some electrons free to move in the piece of metal, there will be a small deficit of electrons on the side closest to the ruler and an equal addition of electrons on the side farther from the ruler. It is not true, as I’ve heard some say, that all the free electrons move from one side to the other. That would destroy the metallic bonds, and the piece of metal would fall apart.
Electrical forces are so inherently strong that the movement of a very small fraction of electrons can produce a large electrical effect.
Electrical polarization is involved is nearly 100% of observable electrical effects. This is why saying that like charge repel and opposite charges attract is not really teaching much about electrical effects.
The paper has induced charges. Electrons which were distributed equally around a molecule are affected by the field of the plastic ruler.
If the ruler is negatively charged, then electrons in the paper molecules (cellulose) are repelled and spend more time at the end away from the plastic ruler. These molecules are slightly negatively charged at the end away from the ruler and positive at the end near the ruler. (But still neutral overall).
THe positive charges are closer to the ruler and so are attracted more thab the negative charges are repelled because these are further away. This tiny chang
The plastic ruler picks up free electrons when rubbed on hair, so it becomes negatively charged. The paper bits, neutrally charged, are more positive than the ruler, and opposite charges attract.
Both the ruler and the paper are insulators, so very little current flows from the ruler to the paper to re-balance the charges, therefore the paper bits continue to be attracted to the ruler.
With small, multiple pieces of paper, the charges get distributed differently in that you end up with little charged ‘plates’ that interact with each other as well as the rod.
Eventually, the force of the charges will build to the point where they stand perpendicular to the rod's surface. Because the physical contact zone at the rod is overcome by the repelling forces exerted by the forces between the larger forces on the paper pieces’ surfaces, after sufficient charge has migrated to them via surface leakage currents, they push each other away, provably even before their capacity to continue to collect charges through contact is even reached.
Think of the paper pieces as a bunch of tiny, wet, thin, flat, soap bars stuck through a special membrane layer of gel almost as thick as the length of the bars. This membrane is attached to a solid base but the ends of each soap bar goes through the membrane and attaches itself to the base with a kind of a wet, sticky adhesion. This medium layer has the ability to increase pressure through a pump. After a certain pressure is reached, the bars will simply start to squirt out of the membrane.
Perhaps this membrane model isn't the greatest analogy of an electrostatic surface charge, but the idea of pressure buildup as a layer effect kind of matches the force network structure here.
The thing is that the real system of the rod and paper bits is a wonderful example of macro meets micro meets quantum, and is one that's so easily demonstrated in an observable time frame.