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### Author Topic: How exactly do neutral items get attracted to charged ones?  (Read 4736 times)

#### pomodoro

• Hero Member
• Posts: 720
##### How exactly do neutral items get attracted to charged ones?
« on: December 02, 2016, 11:55:13 AM »
Here is a question that the net has not been able to answer to my 100% contentment. Perhaps you can.

You all know that a charged comb can attract uncharged bits of paper.

The common answer is this: the comb is (for example) negatively charged by rubbing. When put close to the paper the neg charge pushes  away the electrons in the paper and a positive charge appears on the paper close to the comb . This is electrostatic induction that everyone knows about. Now my problem is that the charge of electrons pushed away is the same as the  charge of the protons now being attracted to the neg charge on the comb. That is the push experienced by the electrons is the same as the attraction of the protons towards the comb.
There should be no net attraction, but of course there is. Does anyone know the exact reason and the formula to calculate the attraction?  The net has lots of vague answers all similar but I could not find a proper believable and somewhat academic one.

#### pomodoro

• Hero Member
• Posts: 720
##### Re: How exactly do neutral items get attracted to charged ones?
« Reply #1 on: December 05, 2016, 04:48:23 AM »
Hey guys just bumping this as I know there are a few people here who know electrostatics well and may have missed the post.  Hows it possible that the a net attraction develops? According to coulombs law the electrons on the paper atoms are being pushed back by the comb by a force which should equal to the attractive force that the protons are experiencing towards the comb. The electrons are still on the same atoms of the paper as it in a non conductor and have not moved. The theory should also work with a positive charge on the comb as once again the neutral paper is then attracted. Weird isn't it??

• Hero Member
• Posts: 1317
##### Re: How exactly do neutral items get attracted to charged ones?
« Reply #2 on: December 05, 2016, 08:21:39 AM »
@pomodoro
Quote
Hey guys just bumping this as I know there are a few people here who know electrostatics well and may have missed the post.  Hows it possible that the a net attraction develops? According to coulombs law the electrons on the paper atoms are being pushed back by the comb by a force which should equal to the attractive force that the protons are experiencing towards the comb. The electrons are still on the same atoms of the paper as it in a non conductor and have not moved. The theory should also work with a positive charge on the comb as once again the neutral paper is then attracted. Weird isn't it??

Nobody wants to answer because Electrostatics is considered the Black Art, lol.

The particle/fields or "charges" do in fact move in the paper just like in the dielectric of a capacitor. The displacement of charges is extremely small however the inverse square law dictates that because there are billions of charges involved a small displacement can produce very large forces. If we could separate the opposite charges in that small piece of paper to a distance of 1 meter the force of attraction would be measured in tons.

AC

#### Jeg

• Hero Member
• Posts: 1532
##### Re: How exactly do neutral items get attracted to charged ones?
« Reply #3 on: December 05, 2016, 12:35:23 PM »
You should check at the triboelectric list of materials. The more negative (comp) due to the stronger nuclei attraction to electrons than paper, steals electrons from paper and so the balance breaks. The comp becomes more negative and paper becomes more positive as it looses electrons. https://www.trifield.com/content/tribo-electric-series/

#### pomodoro

• Hero Member
• Posts: 720
##### Re: How exactly do neutral items get attracted to charged ones?
« Reply #4 on: December 06, 2016, 01:04:13 PM »
I think AC gave the answer that is generally accepted.  I guess it helps thinking of the atom as a more easily comprehended model like a tiny magnet with a N and S very close to each other ,ie neutral when viewed far away, but as soon as a N or S pole is placed near by it lines up and becomes attracted. Swap the N and S with + and - and we have the atomic model. I think its not just the distance that  but the shielding of the charge behind the one in front that strengthens the force.