Force on 2 wires near each other with current

AI Thread Summary
Two parallel wires, each carrying a current of 3.7A and separated by 0.08m, exert a force on each other due to their magnetic fields. The force can be calculated using the formula F = BIL, where B is the magnetic field generated by one wire at the location of the other. A calculation attempt yielded 27.38μN, but the expected answer is 13.69N, indicating a potential error in the magnetic field calculation or assumptions about wire length. The discussion highlights the importance of correctly applying the equations and considering the approximation of wire lengths in relation to their separation. Clarification on the calculations and the validity of the assumptions is sought for accurate results.
D.B0004
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Homework Statement


Two wires are placed parallel near each other in free space at a distance of d=0.08m. They have a length of L=0.4m and each carry a current of i=3.7A (in the same direction.) Find the force exerted on each other. Consider attraction as positive force and repulsion as a negative force.

Homework Equations


F = B*I*L
B= = u*Hs = (u*I/(2*PI*R))*I*L

The Attempt at a Solution


4*PI*10^-7*3.7/(2*PI*.04)*3.7*.4 = 27.38uN
The correct answer is apparently 13.69N. Anyone see where I am going wrong? Is my B equation incorrect? Thanks!
 
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D.B0004 said:
B= = u*Hs = (u*I/(2*PI*R))*I*L
I don't understand what you calculated here.
And I wonder how you got units of tesla out of that calculation (a good check to see if everything went right).

A different issue: the approximation of very long cables (compared to R) you used might not be a good one.
 
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