# Net magnetic field

1. May 4, 2005

### EvaBugs

I have a small question about net magnetic field.

If I have 3 straight conductors that are parallel where
-the current is to the left in conductor #3 (and situated at a distance b from #2)
-the current is to the right in conductor #2. (and is situated at a distance a from #1)
I have to find the net magnetic field exerted by #2 and #3 on the first conductor.

Using RHR I found that:
-conductor #3 , the magnetic field is directed out of the page;
-Conductor #2, the magnetic field is into the page.

To find the net magnetic field, should I use B= KI2/(b+a) - KI2/a

Last edited: May 4, 2005
2. May 4, 2005

### OlderDan

Are the conductors arranged in the order of number? #2 between #1 and #3? And was it supposed to say

and

Last edited: May 4, 2005
3. May 4, 2005

### EvaBugs

Yes, it's supposed to say that. They are placed on top of the other.

4. May 4, 2005

### OlderDan

If I am reading it right, the denominator a+b should be b itself. Are you looking for just the magnetic field, or the force on wire #1?

5. May 4, 2005

### EvaBugs

For the net B on wire #1

-the current is to the left in conductor #3 (and situated at a distance b from #2)
-the current is to the right in conductor #2. (and is situated at a distance a from #1)

6. May 4, 2005

### OlderDan

Then the b+a should be correct

If #1 is on top, then your field directions are reversed. If #1 is on the bottom you have them right

7. May 4, 2005

### EvaBugs

Yes, it is at the bottom

Thank you