Three long wires all lie in an xy plane parallel to the x axis. They intersect the y axis at the origin, y = d, and y = 2d, where d = 10 cm. The two outer wires each carry a current of 6.8 A in the positive x direction.

1. What is the magnitude of the force on a 2.8 m section of either of the outer wires if the current in the center wire is 3.3 A.

(a) in the positive x direction and (b) in the negative x direction?

Answer :

Answer:

[tex]F = 2.55*10^{-4} \ N[/tex]

F = [tex]3.808 * 10^{-6} \ N[/tex]

Explanation:

The magnetic field due to the first wire can be written as:

[tex]B_1 = \frac{\mu _o I_1}{2 \pi (2 d)}[/tex]

[tex]B_1 = \frac{\mu _o I_1}{4 \pi d}[/tex]

The magnetic field due to the second wire is as follows:

[tex]B_2 = \frac{\mu _o I_2}{2 \pi d}[/tex]

The net magnetic field B = [tex]B_1 +B_2[/tex]

[tex]B = \frac{\mu _o I_1}{4 \pi d} +\frac{\mu _o I_2}{2 \pi d} \\ \\ B = \frac{ \mu_o }{2 \pi d}(\frac{I_1}{2}+ I_2)[/tex]

Also; the magnetic force on wire segment  l = 2.8 m

[tex]F = I_1lB = \frac{ \mu_o }{2 \pi d}(\frac{I_1}{2}+ I_2)[/tex]

Replacing all the values ; we have :

[tex]F = \frac{ 4 \pi * 10^{-7}*6.8*2.8}{2 \pi * 10*10^{-2}}(\frac{6.8}{2}+ 3.3)[/tex]

[tex]F = 2.55*10^{-4} \ N[/tex]

b)

Magnetic field due to the first wire is :

[tex]B_1 = \frac{\mu _o I_1}{4 \pi d}[/tex]

[tex]B_1 = \frac{4.0*10^{-7}*6.8}{4 \pi *10*10^{-2}}[/tex]

[tex]B_1 = 6.8*10^{-6} \ T[/tex]

Magnetic field due to the second wire is :

[tex]B_2 = \frac{\mu _o I_2}{2 \pi d} \\ \\ B_2 = \frac{4*10^{-7}*3.3}{2 \pi *10*10^{-2}}[/tex]

[tex]B_2 = 6.6*10^{-6}T[/tex]

[tex]B_1>B_2[/tex]

Net magnetic field B = [tex]B_1 - B_2[/tex]

B =  [tex](6.8*10^{-6} - 6.6*10^{-6})T[/tex]

B = [tex]2*10^{-7} \ T[/tex]

Magnetic force F = [tex]I_1lB[/tex]

F =  [tex]6.6*2.8 *2*10^{-7}[/tex]

F = [tex]3.808 * 10^{-6} \ N[/tex]

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