Magnetic Field and Circuits

Discussion in 'Homework Help' started by f74bat, Dec 1, 2008.

Nov 26, 2008
13
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Two long, straight parallel wires are separated by a distance d. The bottom wire carries a current 14.0 A.

Point C is at the midpoint between the wires and point O is a distance 0.600d below the bottom wire as shown. The total magnetic field at point O is zero. What is the current, I, in the top wire?

I did a similar problem in class but we were given more values. I used the B=(mu*I)/(2*pi*r) and then made B1 and B2 equal to one another..but i don't have enough information to solve it.

Nov 26, 2008
13
0
The second part is:

If the separation distance is d = 0.295 m, what is the magnitude of the magnetic field at point C?

3. mik3 Senior Member

Feb 4, 2008
4,846
63
Calculate B at point O due to the current of the bottom wire. Then calculate the current through the top wire as to create an equal magnitude B at point O. The distance of the top wire form point O is (d+0.6d).

Bottom wire B:

B1=(μ*I1)/(2π*0.6*d)

Top wire B:

B2=(μ*I2)/(2π*(d+0.6*d))=(μ*I1)/(2π*1.6*d)

Then

B2=-B1

thus

(μ*I1)/(2π*1.6*d)=-(μ*I1)/(2π*0.6*d)

thus,

I2=1.6*I1/0.6

For the second part of the question, calculate B at point C each wire creates and then add them to get the total B (note that one B will come out negative because it is in the opposite direction of the other conductor's B).