# Homework Help: Magnitude of electric charges

1. Aug 23, 2008

### kdaerdna

Given three charges fixed along the x-axis and their length from the origin, how do I find their magnitude in C's?

2. Aug 23, 2008

### rock.freak667

Are you familiar with Coloumb's Law?

3. Aug 23, 2008

### kdaerdna

Yes, I am. I know how to use the law to find the magnitude of the Forces created by the electric charges, but I can't figure out how to find magnitides of the charges themselves!

4. Aug 23, 2008

### LowlyPion

You have 3 unknowns - the 3 charges - you know their coordinates.

How many equations do you need to solve for the unknowns?

5. Aug 23, 2008

### kdaerdna

Here is the problem: Two charges are fixed on the x axis: one with a charge q1=5.00*10^-6 C at x1=-1.00m and the other with a charge of q2=3.00*10^-6 C at x2=1.50m. Find the force on a charge q=-5.00 *10^-6C placed at the origin (x=0).
***What are the magnitudes of the three charges q,q1, and q2? Express your answer in coulombs*****So, I know how to find the first part, the Force, but I don't know what they are meaning in the second question with the magnitudes.

6. Aug 23, 2008

### rock.freak667

The question is asking you to find q,q1 and q2 when they gave you those values in the question?

7. Aug 23, 2008

### kdaerdna

Yeah, isn't that weird. I typed the question ecaxtly like it is asking it. What do you think?

8. Aug 23, 2008

### LowlyPion

That would be a different problem than the general one you posted. As a first recommendation I would suggest in the future that you use the template for presenting a problem in the forum and provide the entire statement of a problem if you have a question.

I am further presuming that you have correctly used Coulomb's Law to calculate the force contributions from each of the charges.

Given the statement of your problem the values are apparently given, so either there is some other piece to it still not disclosed or they are asking you merely for a recitation of the values they have provided.

9. Aug 23, 2008

### Phrak

I think if you give the magnitude and direction of the of the force on each particle, no one should have reason to complain.