Don't know where to begin mag field question

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The discussion revolves around calculating the magnetic field at three specific points due to two parallel current-carrying wires. The user is unsure about the initial steps and the appropriate formulas to use, specifically questioning the application of Ampere's Law. Calculations for the magnetic field at Points A and B are provided, with the user seeking confirmation on their approach and the correct value for the radius in the equations. Key advice includes being cautious with the direction of the magnetic fields and defining a positive direction before proceeding with calculations. The conversation emphasizes the importance of clarity in applying physics principles to solve the problem effectively.
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Don't know where to begin...mag field question

1. Homework Statement

http://s685.photobucket.com/albums/vv212/dewdr0p714/?action=view&current=physicsexam2q2.jpg

Each support string connects to a corner of the rectangular ceiling. The current carrying wires are .5m apart. The current carrying wires have a mass per unit length of .150 kg/m. The currents are identical and in opposite directions.
Point A is 1m away from the wire on the right
Point B is exactly between the 2 wires
Point C is 1.5 m away from the wire on the left

(all the points are in the same plane as the 2 wires)

b) Determine the magnetic field B at Point A, Point B, and Point C

2. Homework Equations

i think this formula is supposed to be used but I'm not sure...B = F / |q0|(vsinθ)



3. The Attempt at a Solution

I just don't know where to begin with this problem...can anyone give me any pointers?
 
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hi dewdrop, do you know amperes law?

the equation you gave is for force on a moving charge in a magnetic field
 


i tried to solve the problem...can someone please check my work? i think i may have made a mistake somewhere along the way
I = 300 is given for the question

B for Point A = [μ0I / 2pi]*[(1/x) - (1/r+x)] = (4pi *10^-7)(300) / (2)(pi) * (1/1m) - (1/1.5m) = 1.97*10^-4 T

B for Point B = 2μ0I / (pi)(r) = 2*(4pi *10^-7)(300) / (.25)(pi) = 9.6 *10^-4 T

***i guess my biggest question is what am i supposed to use for the radius value?
 


r will be the distance from the point to the current carrying wire

points
- be careful with direction, at each point is the magnetic field from each wire up, or down?
- define a positive direction before attempting the problem
- eg. B is +ve in the up direction
- also writing B = 2μ0I / (pi.r) makes more sense as we know what is divided by

that said, your first calc looks ok (field opposite directions)
2nd 2 contributions at radius of 0.25 - also looks good
 
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thanks for your help! =]
 
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