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Unformatted text preview: Physics 251 Laboratory Magnetic Fields Pre-Lab: Please do the pre-lab exercise on the web. Introduction By now, you have studied methods for calculating the magnetic field due to current traveling in a wire. In particular, the Biot-Savart law is r B = m 4 p Id r l × ˆ r r 2 ∫ Using this, you can find the magnetic field at the center of a circular, current-carrying wire loop. r B = m I 2 R In this lab, we will observe the effects of such a field, using a compass needle as a detector. As a final result, we will calculate the magnitude of the horizontal component of the Earth’s magnetic field, which we will label B Earth,H . Equipment/Supplies Glass jar, wooden frame, wire, compass, power supply, ammeter, patch cords and connectors. Section 1 Place the compass in the indentation on the wooden frame, and slip the glass jar over the end of the frame. When you wind the wire in a coil around the jar, you will want the compass to be located as nearly as possible in the center of the coil. Your only magnetic field sensor is a compass. The compass is a useful device if you are lost in the woods, but it can only tell you the direction of a magnetic field. It cannot tell you the magnitude. We can overcome this difficulty by using the playing the Earth’s magnetic field magnitude....
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This note was uploaded on 11/12/2009 for the course PHY 303L taught by Professor Turner during the Spring '08 term at University of Texas.
- Spring '08