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Magnetic force on a wire 
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#1
Nov2208, 03:12 PM

P: 360

1. The problem statement, all variables and given/known data
A packed bundle of 100 long, straight, insulated wires forms a cylinder of radius R = 0.500 cm. (a) If each wire carries 2.00 A, what are the magnitude and direction of the magnetic force per unit length acting on a wire located 0.200 cm from the center of the bundle? 2. Relevant equations [tex]F= ILB[/tex] [tex]B = \frac{\mu_{0}I_{enc}}{2\pi r}[/tex] 3. The attempt at a solution Here is what I did to get the solution: I can find the number of wires in out to where the radius equals 0.002m. [tex]\frac{\pi(0.002)^2}{\pi(0.005)^2}*100 = Number of Wires[/tex] That gives me 16 wires and since each has 2 amps the current enclosed = 32 A. Using ampere's law: [tex]B = \frac{(4\pi * 10^{7})(32)}{2\pi(0.002)}[/tex] B = 0.0032 Knowning B I can find the force per unit length on one wire with 2 amps of current. [tex]\frac{F}{L} = (2)(0.0032)[/tex] That equals 0.0064 N/m That answer is wrong and I can't figure out why. If anyone can help it would be appreciated. Thanks 


#2
Nov2208, 03:28 PM

P: 46

Do you mean .0064N/m



#3
Nov2208, 03:34 PM

P: 360

yes I did, sorry



#4
Nov2208, 08:09 PM

P: 360

Magnetic force on a wire
I can't figure out what could be wrong with this.



#5
Nov2208, 08:13 PM

P: 166

Looks okay to me too..



#6
Nov2408, 07:09 PM

P: 3

The instructions request the direction as well as the magnitude...
You have the magnitude: 6.34mN/m I'd say you need to articulate the direction ("inward"), ,otherwise you are absolutely correct. 


#7
Nov2408, 07:49 PM

P: 360

Well I got an answer of 6.4mN/m which is not the right answer. 3 options. Something is wrong in my logic. Something is wrong in my calculations. Or the books is wrong.



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