(Finding the Magnetic Field Strength)
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Contents
Diagram 1.1
Data Table 1.1

 The purpose of this preliminary investigation was to determine the specific magnetic fields of the magnets I was using in my observation. After going through many different setups. I decided that the best way would be to create a uniform magnetic field that canceled the magnet's field lines. I would then use a small, very sensitive test magnet to find the current needed to cancel the unknown magnet's field (This would be found at the point where the compass magnet could go either direction perpendicular to the field). I made the solenoid out of a pop bottle by neatly wrapping an insulated wire around it. The solenoid had 198 turns in a distance of 0.123952 meters.
 Diagram 1.1 TOC
 (Solenoid Set-Up)

The equation for a magnetic field created in the center of a solenoid is:
B =
l o*(N/L)*I, where N/L is the number of loops per length.
For me this value was
198/0.123952, or 1597.4, so, simplified my equation is

B » 0.00200734*I

 Since I had no choice but to do this on Earth, I had to deal with the magnetic field already in existence. To solve this I always had the magnetic field lines facing from north to south. I found the Earth's magnetic field to be at a current of 10.33mA, which corresponds to a magnetic field of 2.07358E-5 Teslas. This is actually fairly close to the 5.00E-5 Teslas give by Giancoli (Giancoli, 1991: 533). I don't think that this difference of about 2.9264E-5 Teslas represents an error, but an angle of dip of the Earth's B-field. In other words the horizontal component is 2.07358E-5 Teslas. This is supported by the fact that in Cambridge, Massachusetts the horizontal component is about 1.7E-5 teslas, which isn't far magnetically, from Portland, Oregon (Zemansky, 699). Therefore, for my experiment the equation for the actual magnetic field of the magnet would be: Bmagnet + Bearth = Bsolenoid
 Data Table 1.1 TOC

Magnetic Field Data

(Small Ceramic Magnet)

 Meters mA Solenoid B-Field Magnet B-Field 0.06033 246.2 0.00049 0.00047 0.0635 211.4 0.00042 0.0004 0.06985 171.5 0.00034 0.00032 0.0762 126.8 0.00025 0.00023 0.0889 86.8 0.00017 0.00015 0.1016 63 0.00013 0.00011 0.1143 46.2 9.3E-05 7.2E-05 0.127 37.2 7.5E-05 5.4E-05 0.1397 30.65 6.2E-05 4.1E-05 0.1524 26.2 5.3E-05 3.2E-05 0.1651 22.34 4.5E-05 2.4E-05 0.1778 20.65 4.1E-05 2.1E-05 0.1905 18.91 3.8E-05 1.7E-05 0.2032 16.6 3.3E-05 1.3E-05 0.2159 15.9 3.2E-05 1.1E-05 0.2286 15.51 3.1E-05 1E-05 0.2413 14.87 3E-05 9.1E-06 0.254 14.42 2.9E-05 8.2E-06

data file

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