zhang20 - 2/14/2010 First exam: 02/22/09, Saturday; 12-2pm...

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2/14/2010 1 First exam: 02/22/09, Saturday; 12-2pm Covers: Ch15-Ch18 Format: 12 MC (3 MC/chapter): 12x3 = 36 points 4 problems (one per chapter): 4x16 = 64 points Formula sheet: One letter size, both sides Room assignment: Check for announcement Makeup exam: Check for announcement Students with disabilities: Please contact your office for exam scheduling. Induced Voltages and Inductance How does electric generator work?
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2/14/2010 2 A carton box A strong bar magnet A small flashlight light bulb A long thin conducting wire (with insulating layer) One of the greatest scientists in history Invented electric motor, generator and transformers Discovered electromagnetic induction Discovered laws of electrolysis 1791 1867
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2/14/2010 3 A current can be produced by a changing magnetic field (more precisely, changing magnetic flux ) First shown in an experiment by Michael Faraday A primary coil is connected to a battery A secondary coil is connected to an ammeter First observation: An electrical current is produced by a changing magnetic field Careful analysis: The emf is actually induced by a change in the quantity called the magnetic flux rather than simply by a change in the magnetic field How can you tell it is the changing field or flux that matters? What is magnetic flux?
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4 A current loop in a uniform magnetic field The loop has an area A The magnetic flux is defined as where θ is the angle between B and the normal direction of the plane Normal <-> perpendicular B ) cos( BA A B B When the field is perpendicular to the plane of the loop (a) θ = 0, Φ B = Φ B, max = BA When the field is parallel to the plane of the loop (b) θ = 90° , Φ B = 0 SI units of flux are T . m² = Wb (Weber)
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This note was uploaded on 03/15/2010 for the course PHY 102 taught by Professor Luo during the Spring '08 term at SUNY Buffalo.

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zhang20 - 2/14/2010 First exam: 02/22/09, Saturday; 12-2pm...

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