## Two current carrying wires. Confusion

1. The problem statement, all variables and given/known data

Let there be two current carrying wires with current flowing in the same direction. According to my book, they attract by the right hand rule. Now here is my question, since the B-field is popping inwards for one of the wires and the other one is popping outwards in the middle between the two wires, wouldn't that mean the B-field is 0? If it is then how can the B-field come back outwards and inwards again?
 PhysOrg.com science news on PhysOrg.com >> New language discovery reveals linguistic insights>> US official: Solar plane to help ground energy use (Update)>> Four microphones, computer algorithm enough to produce 3-D model of simple, convex room

 Quote by flyingpig If it is then how can the B-field come back outwards and inwards again?
I cant understand what you are asking
 Here is a picture Uploaded with ImageShack.us Now in the middle region is it 0?

## Two current carrying wires. Confusion

Yes it is
 Then how can the Field come back in and out on the far right and left?

Mentor
 Quote by flyingpig Here is a picture Uploaded with ImageShack.us Now in the middle region is it 0?
Yes it's zero there, but what maters is what the B field is at the location of each wire.

 Quote by flyingpig Then how can the Field come back in and out on the far right and left?
Why then can't? they are two independent fields ...

like for electric field ... if you place a conductor in its path ... it is zero inside it but again gains its strength outside it

 Quote by cupid.callin Why then can't? they are two independent fields ... like for electric field ... if you place a conductor in its path ... it is zero inside it but again gains its strength outside it
But is the B-field only 0 at the mid point? Or is it everywhere between the two wires
 Mentor Think about this in three dimensions. The ONLY place the B field is zero is right along the line that's midway between the wires.
 only at the mid point because only at that point their strengths become equal and opposite Edit: Mag field due to long wire, $$\vec{B}= \frac{\mu_{o}}{2\pi}\frac{i}{d}$$
 Just one other question, I noticed the "finger" cross product rule is different from the wrap around right hand rule (not the curl one, like most calculus textbook teaches one) and this observation uses the wrap around the current rule
 Mentor Be more specific. Are you referring to the rule which gives the direction of the B field around a current carrying wire, as "the wrap around right hand rule" ?
 Yes that one. Another question If I want to find the B-field created by the wire on the left, why would I use the distance between the wires? Let d be the distance between the wires, so shouldn't I use d + x where x is a positive quantity.

Mentor
 Quote by flyingpig Yes that one.
That's NOT a cross product at all. (Referring to the wrap around rule)

One question at a time, please! Your threads tend to get convoluted when you have multiple questions and/or topics in one post.

 Another question If I want to find the B-field created by the wire on the left, why would I use the distance between the wires? Let d be the distance between the wires, so shouldn't I use d + x where x is a positive quantity.