# Lab_7 - Physics 272Lab Lab 7: Magnetic Field of...

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Physics 272Lab Lab 7: Magnetic Field of Current-Carrying Wires Lab 7: Magnetic Field of Current-Carrying Wires OBJECTIVES In this lab you will Measure the deflection of a compass needle due to a magnetic field of a wire Test the relation between current and magnetic field strength Calculate the distance dependence of the magnetic field from a wire You have seen in class how a moving charge will create a microscopic magnetic field. You have also seen how a large number of moving charges (current) will create a macroscopic magnetic field given by: 0 2 0 ˆ μ I Δl ×r ΔB= 4 πε r You can measure this macroscopic field with a simple compass. 1) Warm-Up Problem Problem (1) What is the direction of the magnetic field at the indicated locations inside and outside this current carrying rectangular coil of wire shown? Explain briefly. CHECKPOINT 1: Ask an instructor to check your work for credit. You may proceed while you wait to be checked off 2) Measuring a Magnetic Field with a Compass a) Get out the following items for this lab: 1 short bulb with holder 3 batteries with holder (you may need to temporarily borrow the third battery) 4 alligator clips 1 long wire 1 compass b) Put away everything else (except your lab manual), so your table is neat and clear.

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Physics 272Lab Lab 7: Magnetic Field of Current-Carrying Wires c) Make a circuit with two-batteries, a short bulb, the long wire, and the four alligator clips (Fig. 1). Leave one end of one of the alligator clips unconnected (bulb not lit). d) Place your magnetic compass on a flat surface Make sure the compass is not near steel objects, such as the circuit you just made, and the computer. e) Once the compass needle settles, align the north marker with the red end of the compass needle. f) Continue aligning the compass until, at rest, the red end of the needle is aligned with the north marker. g) Stretch your long wire out straight, running north-south. h) Make the last connection so that the bulb glows (the bulb must glow). i) Lift the wire up above the compass. Keeping it stretched out north-south. j)
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## This note was uploaded on 04/23/2011 for the course PHYS 272 taught by Professor K during the Spring '07 term at Purdue University.

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Lab_7 - Physics 272Lab Lab 7: Magnetic Field of...

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