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feedmeister

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## Homework Statement

A bar magnet with magnetic dipole moment

**0.51**A m^2 lies on the negative x-axis, as shown in the diagram. A compass is located at the origin. Magnetic North is in the negative z direction. Between the bar magnet and the compass is a coil of wire of radius

**1.5**cm, connected to batteries not shown in the picture. The distance from the center of the coil to the center of the compass is

**9.2**cm. The distance from the center of the bar magnet to the center of the compass is

**22.5**cm. A steady current of

**0.632**amperes runs through the coil. Conventional current runs

**clockwise**in the coil when viewed from the location of the compass.

**How many turns of wire are in the coil?**

## Homework Equations

[tex]B_{loop} = \mu_{0}2\pi R^{2}I/{4\pi}(z^{2}+R^{2})^{3/2}[/tex]

[tex]B_{magnet} = \mu_{0}2\mu/4\pi r^{3} [/tex]

[tex]B_{earth} [/tex]= 2 E-5 Tesla

[tex]\mu_{0}/4\pi = 10^{-7}[/tex]

I = 0.632 A

[tex]\mu = 0.51 A m^{2}[/tex]

## The Attempt at a Solution

I have been trying to do # of turns = [tex](B_{earth} - B_{magnet}) / B_{coil}[/tex]

and got 100.1271 but it's not the right answer. Can anyone help with what I'm doing wrong?

Attached is a diagram of the problem.

Thanks and regards,