# Electrostatics - Coulomb's Law

Discussion in 'Physics' started by Nirvana, Aug 20, 2006.

1. ### Nirvana Thread Starter Well-Known Member

Jan 18, 2005
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Charles Augustin Coulomb June 14, 1736 - August 23, 1806. Was a French Physicist.
Coulomb created a device known as a torsion balance which could accurately calculate the force exerted between point charges. This force was explained as such: "The force exerted between two point charges is equal to the product of their strength and inversely proportional to the square of the distance between them". This statement/law is known as Coulomb's Law or The Inverse Square Law.
As a formula this becomes:F = (Q1 * Q2)/(r2)
In vaccum or free space this formula is adapted to include the constant of proportionality which is 1/4π. Also in free space the permittivity of free space is equal to 1/36π x 10-9(given the greek letter ε (epsilon) o = εo), the fromula becomes.
F = (Q1 * Q2)/4π εo r2
Although a useful concept it would be beneficial to know the strength the force exerted on the other charge, known as the electric field strength/intensity. To do this one charge is fixed say Q1 and the other Q2 is allowed to move. To calculate the force per unit charge or rather force per Q2 we divide the formula for Coulomb's Law by Q2, giving a new vector E which is;
E = Q1/4πεor2
We now have a way of determining the strength of an electric field, or the force field of one (fixed) charge acting on another (moveable) charge.

Remembering that the electric field strength is defined as a moveable point charge in the vicinity another fixed charge of the same polarity. An analogy to describe the Force (F) and Electric Field Strength (E) would be to use two magnets;
Take two magnets each with its own North and South Poles (Naturally), now if we move the two magnets towards each other(the direction of the poles e.g. whether north or south are facing each other, is irrelavent) a force is experineced whether it be a force of attraction or repulsion. The force F is that force exerted between the two magnets.
If we now fix the position of one magnet but allow the other to be brought nearer to the other fixed magnet, then what we would notice is that the force which is experienced is that force which the fixed magnet has on the moveable one. Meaning we can now measure the electric field strength of the fixed magnet by noticing how strong the force of attraction or repulsion is on the moveable magnet.

NOTE: The writing package won't allow me to use the power notation, particularly power of 2, so in the above formulae please take the number 2 after a letter/variable to mean square, as in algebra numbers come before variables anyway, thank you)

Nirvana.

2. ### RhinosarusDinosarus New Member

Jun 26, 2014
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Exactly how does Coulomb's Force apply to electronics? Does it even have anything to do with electronics?

Would love to know.

Thanks,
RD

Aug 27, 2009
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4. ### dougc314 Member

Dec 20, 2013
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There are plenty of electrostatic devices through the ages. I have an X-Y plotter that holds the paper down electrostaticly. For a up to date very modern application of electrostatics in electronics google "electrostatic mems" and read away.

5. ### alfacliff Well-Known Member

Dec 13, 2013
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xerox copiers use electrostatics for copying. charcoal cookers use electrostatic (piezoelectric) igniters. anyone interested in esd should get to know electrostatics.

6. ### amilton542 Active Member

Nov 13, 2010
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I can't remember off the top of my head, but electrostatics is utilised in power plants in such a way it filters the waste smoke ready for discharge into the atmosphere.

7. ### alfacliff Well-Known Member

Dec 13, 2013
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electrostatic precipatators. remove particulates from smoke.

8. ### BR-549 Well-Known Member

Sep 22, 2013
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Electrostatics is the father of electronics. It is the E in E=IR. It powers and initiates most circuits. The electric field radiates from charge. And charge is everything. All energy, force and matter come from charge.

9. ### RhinosarusDinosarus New Member

Jun 26, 2014
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So then does Coulomb's Law apply to inter-molecular forces? Is that how it works? It attracts / repels based on the amount of protons / electrons an object contains?

So, if, for example, an atom has 5 Protons & 7 Electrons, it will be attracted to the Positive Charge?

And the same to be true if it were say 50 Protons & 10 Electrons, but this time it would be attracted to the Negative Charge & with more force?

Is this how objects hold themselves together? Like Plastic, Metal, Rocks, etc. ?

Sep 22, 2013
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11. ### BR-549 Well-Known Member

Sep 22, 2013
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So an atom....just like a particle, is held together by two opposing electric and magnetic fields. Now....to be classified as a fundamental particle.....it must be stable. To be classified as an atom.......it must be stable also. One electron and one proton do not form a stable atom. Almost any external electric or magnetic field will break it up. That why you dont see much H1 around. Now there are many, most physicist, astronomers and some chemist that will tell you that H1 is the most abundant element in the universe. It is not. A proton by itself is not ionized H1. Its a proton. Now...look at my icon. That is the smallest atom. Its hydrogen. This is the first element. This is the smallest piece of stable matter. The large circle connecting the four particles represents the magnetic field holding the atom together. When we look at the atom(and we will be able to), all you would see is the four loops. And you could not see the loops until they radiate......because the magnetic field of the particle keeps them invisible. All 4 particles are lined up magnetically. And all of that field goes thru all particles and it syncs and it rotates, it is very, very strong. Quantum physicists call this the strong nuclear force, but we now know what this is. The electric force is balanced and keeping the particles equal-distant from each other. The small loops are protons and the big loops are electrons. Now I have to go back to the free electron for a moment. A free electron is siting in space. As a free space, low energy electron.....as the charge rotates one time around the loop or ring.......it twists once......makes one spring coil per one loop rotation. Now the electric field and the magnetic field of the electron is in tune. It resonates. The frequency of the electron resonance is the wavelength of the circumference of the loop. Now there is only one electron in the universe and it is dark. One billion miles away I turn on a bright multi-spectrum light source. When the light finally reaches the electron.......it ignores all except that one frequency that is equal to the circumference wavelength. It starts absorbing the electric and magnetic field energy from the light. As it absorbs energy, the E and H fields of electron build up. The charge wants to speed up.......but it already going at the speed of light....so when the energy builds up enough.....instead of going faster.......it adds another twist. Now when it gained enough power to make a new twist......it changed the circumference of the loop(the circumference went down,the electron loop got smaller).......and stopped absorbing power at that frequency. Now if there is light at the new circumference frequency.....it will start absorbing more light. Now turn the light off. Now the electron is sitting there in the dark at a high energy state and it does not like it. All particles like to calm. To lose(relax) that extra twist......it changes its circumference back to the norm. When that radius(circumference) expands....it momentarily cuts the magnetic field and emits the same power and frequency that it absorbed. I present to you the electron. The PRIME radio receiver and the PRIME radio transmitter. The birth place of light. The PRIME radio repeater. What a most beautifully simple and elegant device! OK...you can think on that, I gotta take a break.

12. ### BR-549 Well-Known Member

Sep 22, 2013
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Last edited: Jun 30, 2014
13. ### russ_hensel Well-Known Member

Jan 11, 2009
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BR-549's ideas are interesting, but I think a bit off the rails. I do not want to get into a big discussion, but reader beware.

14. ### studiot AAC Fanatic!

Nov 9, 2007
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Good point Russ!

But some of the statements are just plain wrong.

Charge is never neutral.

Edit: note also that the original post is getting on for 10 years old.

Last edited: Jul 2, 2014

Sep 22, 2013
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16. ### Wendy Moderator

Mar 24, 2008
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This is not the place to do it. Long verbage does not make you right, especially a single run on hard to read paragraph. It just makes for a hard to read post that most of us don't have time for. If you want to present ideas outside of mainstream science then be prepared to back them up with citations and facts. Experimental evidence is the core of real science, not opinion. And has been said, you are stating facts to back up your opinions that simply aren't true.

I let the original hijack go because it was on topic, and fair game for discussion. The moderating staff may have blown it a bit on this one, but we do our best. We may yet split some posts off into their own threads after some discussion.

Last edited: Jul 4, 2014
17. ### studiot AAC Fanatic!

Nov 9, 2007
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@BR-549

Did you have a point to make?

Sep 7, 2013
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@BR-549