Electric Charges: Opposite Attract, Same Repel

[Soaring Crane]

Why do electric charges of opposite sign attract each other but charges of the same sign repel each other?

 

[ranger]

Well there is something called the electric field. By convention, the electric field lines radiate from the positive particle and moves to the negative particle. With that said, once a electron in next to a proton, the field lines will move from positive(proton) to the negative(electron) and act like an attractive force. Likewise, if two protons are next to each other, there is no reason for the field lines to move from + to +, so instead they repel each other.

Note these field lines are abstract and are just used to visualize the electric field.

 

[ranger]

Here is a simulator that shows how the field lines are affected by different particles (electron and proton). It is very useful, you can even drop a test charge (+ or -) into the electric field and trace is path to see which particle it will move towards.

http://www.vias.org/simulations/simusoft_efield.html

 

[Claude Bile]

I don't think anyone has come up with a suitable explanation as to why this is, (if anyone has I would love to hear it) it's one of those fundamental things that cannot be explained using a 'more fundamental' concept.

Claude.

 

[americanforest]

I was thinking about just the same question today. Atoms need to stay neutral, so that's why they attract opposite charges, but why do they repel positive charges. It doesn't help them gain neutrality, does it?

 

[ranger]

I was thinking about just the same question today. Atoms need to stay neutral, so that's why they attract opposite charges, but why do they repel positive charges. It doesn't help them gain neutrality, does it?

I'm confused by what you are trying to say.

 

[americanforest]

I'm confused by what you are trying to say.

Atoms want a full valence shell. To achieve this they attract positive or negative charge as necessary. This makes sense and gives an explanation of why opposite charges attract. Now I'm trying to think of an explanation of why charges of the same sign repel. It doesn't bring the atom any closer to a full valence shell, so that is not a valid explanation.

 

[ranger]

Atoms want a full valence shell. To achieve this they attract positive or negative charge as necessary. This makes sense and gives an explanation of why opposite charges attract. Now I'm trying to think of an explanation of why charges of the same sign repel. It doesn't bring the atom any closer to a full valence shell, so that is not a valid explanation.

Ah, okay. Well atoms don't "attract" charges because atoms are neutral. It is not necessary to have a full shell either, the shell can also be empty. Example, sodium which has 2/8/1 electron configuration, will easily give up an electron and become 2/8 sodium ion. Also only electrons are exchanged among atoms, they don't attract positive charges (protons). Can you imagine electrons and protons "orbiting" the nucleus of the atom?

As for the explanation of attraction and repulsion among electric charges, the best explanation that I know of is by using the electric fields.