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Electromagnetic Induction
Chapter 33 Electromagnetic Induction Phys Chapter 33
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Demo Faraday Phys Chapter 33
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Some experiments Phys Chapter 33
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Motional emf Phys Chapter 33
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Motional emf (cont.) Reach equilibrium Phys Chapter 33
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Problem 33.1 A potential difference of V is developed across a 10-cm long wire as it moves through a magnetic field at 5.0 m/s. The magnetic field is perpendicular to the wire axis. What are strength and direction of field? Phys Chapter 33
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Problem 33.1 (ans) At equilibrium Fm Fe Out of page
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Induced current --moving charges in B field, force --> current
--current-carrying wire in field, force Phys Chapter 33
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Do workbook 33.1 Phys Chapter 33
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Eddy currents Phys Chapter 33
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Do workbook 33.2 & 4 Phys Chapter 33
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Eddy currents (cont.) Phys Chapter 33
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Demo eddy currents Phys Chapter 33
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Do workbook 33.5 & 7 33.5 & 7 Phys Chapter 33
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Magnetic flux Phys Chapter 33
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Do workbook 33.9 & 11 Phys Chapter 33
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Lenz’s law There is an induced current in a closed, conducting loop if and only if the magnetic flux through the loop is changing. The induced current creates an induced magnetic field which opposes the change in flux. --changing flux produces induced current --induced current creates induced field --induced field opposes the change Phys Chapter 33
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Do workbook 33.12, 13 & 19 Phys Chapter 33
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Problem 33.9 The current in the solenoid is decreasing. The solenoid is surrounded by a conducting loop. Is there a current in the loop? If so, is the current in the loop cw or ccw? Phys Chapter 33
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Problem 33.9 (ans) Find change in flux Initially ∆ B1
Change in flux to left Find induced field later Induced field points to right B2 Find induced current Induced current is clockwise from behind Phys Chapter 33
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Induced fields field is there independent of wire
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Faraday’s law --law of nature --usually helpful -field can change
-area can change -both can change Phys Chapter 33
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Do workbook 33.21 Phys Chapter 33
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Problem 33.12b The loop is being pushed out of the 0.20 T magnetic field at 50 m/s. The resistance of the loop is 0.20 . What are the direction and magnitude of current in the loop? Phys Chapter 33
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Problem 33.12b (ans) L w Counter-clockwise Phys Chapter 33
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Problem 33.35 Two 20-turn coils are tightly wrapped on the same 2.0-cm-diameter cylinder with 1.0-mm-diameter wire. The current through coil 1 is shown. A positive current is into the page at the top of the loop. Determine the current in coil 2 as current vs. time t = 0 s to 0.4 s. (Assume field of coil 1 passes completely through coil 2. 0.1 0.3 Phys Chapter 33
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Problem (ans) (+) I1 d2/dt B1 2 2 I2 Phys Chapter 33
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(+) I1 I2 Problem 33.35 (ans) Right to left through resistor
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Generator Phys Chapter 33
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Transformer Phys Chapter 33
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Coulomb and non-Coulomb electric fields
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Maxwell and induced magnetic field
-symmetric in E and B Phys Chapter 33
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E & M equations Phys Chapter 33
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Maxwell’s equations Phys Chapter 33
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Maxwell-no charges or current
+math Light is an E&M wave!!! Phys Chapter 33
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EM waves Phys Chapter 33
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Problem 33.49 A U-shaped conducting rail that is oriented vertically in a horizontal magnetic field. The rail has no electrical resistance and does not move. A slide wire with mass m and resistance R can slide up and down without friction while maintaining electrical contact with the rail. The slide wire is release from rest. Describe the motion of the slide wire. Find the terminal velocity of the slide wire Phys Chapter 33
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