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Two Parallel Wires( in 2 hrs!) 
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#1
Oct1707, 02:30 PM

P: 605

1. The problem statement, all variables and given/known data
Two long parallel wires are a centertocenter distance of 1.50 cm apart and carry equal antiparallel currents of 1.80 A. Find the magnetic field intensity at the point P which is equidistant from the wires. (R = 4.00 cm). 2. Relevant equations [tex] B= \frac{u_{0}I}{2\pi r} [/tex] infinite wire 3. The attempt at a solution Ok I have been workin this problem for a while. In terms of vectors, the y's cancel out. For the X direction I get: [tex] B_{totalx}=\frac{u_{0} I R}{\pi \sqrt( (d/2)^2 +R^2)}[/tex] I dont get why I am wrong, I took the sum of the bfields in terms of vectors. And no the answer is not 0 T! 


#2
Oct1707, 02:45 PM

P: 68

Why do you think that the Magnetic field is not zero?



#3
Oct1707, 02:49 PM

P: 605

Thats what I thought originally , but it is incorrect.



#4
Oct1707, 03:03 PM

P: 68

Two Parallel Wires( in 2 hrs!)
If they have equal, antiparallel currents, and it's a point that's equidistance from the wires, then the answer has to be zero. Unless you decide to ignore the fact that magnetic fields are vectors.



#5
Oct1707, 03:12 PM

P: 1,127

Antiparallel.



#6
Oct1707, 03:15 PM

P: 605

there is something else I am missing. 


#7
Oct1707, 03:50 PM

P: 605




#8
Oct1707, 03:52 PM

P: 1,127

Go back and ask your instructor what he means by antiparallel. It has more than one meaning. It shouldn't but it does.



#9
Oct1707, 04:00 PM

P: 605

I agree, word choice could be better.
However I don't have contact with my prof. right now, this assignment is due in an hour. 


#10
Oct1707, 04:02 PM

P: 68

If I was you I would give your best guess (ignore that you know it's "not right") and argue for points later. Chances are others having the same problem.



#11
Oct1707, 04:04 PM

P: 19

perhaps his answer is wrong by mistake? talk to other people in the class



#12
Oct1707, 04:17 PM

P: 605

he is not, there is an answer I people got. There is some trick though, but my math tells me otherwise,



#13
Oct1707, 04:50 PM

Sci Advisor
HW Helper
P: 2,887

It's when the currents are in the same direction that the total B field is zero at the point midway between them. 


#14
Oct1707, 05:23 PM

Mentor
P: 41,315




#15
Oct1807, 06:32 AM

P: 1,127

OK, now that I can see your diagram, I see the instructor used antiparallel in the correct sense.



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