# Does the difference in charge play a role in electromagnetism such as

1. Sep 22, 2008

### cam875

does the difference in charge play a role in electromagnetism such as a +8 charge pulling a -1 being stronger because of the difference in numbers or does that even matter i mean would that mean that that is stronger compared to a + 1 charge pulling a -1 charge. Thanks in advance.

2. Sep 22, 2008

### atyy

Re: electromagnetism

Yes, it matters: F=kq1q2/r2

It might be interesting to consider the motion of a test charge between two infinitely large parallel conductors. Does (+1,-1) and (+2,0) produce the same result?

I'm not sure I've that up correctly, but take a look at the method of images:
http://farside.ph.utexas.edu/teaching/em/lectures/node64.html

3. Sep 22, 2008

### tiny-tim

Coulomb's law

Hi cam875!

It's not the difference in charge, but the product of the charges, that matters (and also the distance, of course ).

So a +8 and a -1 (or a -8 and a +1) pull each other twice as strongly as a +4 and a -1.

See Coulomb's law

4. Sep 22, 2008

### cam875

Re: electromagnetism

cool thanks for the help very interesting. so are u saying that because (+8) + (-1) is 7 and (+4) + (-1) is 3 that there is a little more than double the attraction in the first example.

Last edited: Sep 22, 2008
5. Sep 22, 2008

### atyy

Re: electromagnetism

No. I believe what tiny-tim is very correctly saying is in the first example, the attraction between two point charges a fixed distance apart ~(+8)(-1)=-8 units, in the second example, the attraction is ~(+4)(-1)=-4 units. So the attraction is exactly double in the first example compared to the second.

I really second his recommendation that you look up Coulomb's law.

6. Sep 23, 2008

### tiny-tim

atyy atyy atyy!

I agree entirely with atyy.

7. Sep 23, 2008

### cam875

Re: electromagnetism

oh ok so your multiplying the charges instead of adding them. makes sense and im going to look at that law, thanks for the help.