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2005 answers Elec

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Unformatted text preview: rights reserved. Visit apcentral.collegeboard.com (for AP professionals) and www.collegeboard.com/apstudents (for AP students and parents). 4 AP® PHYSICS C ELECTRICITY & MAGNETISM 2005 SCORING GUIDELINES Question 2 15 points total (a) Distribution of points 3 points The current through the inductor is zero immediately after the switch is closed ( I L = 0 ) . Using Ohm’s law V = IR For the correct substitution of the emf e for the voltage V For the correct substitution of the total resistance Rtot 1 point 1 point Rtot = R1 + R2 e = Iinit ( R1 + R2 ) For the correct answer I init = e ( R1 + R2 ) (b) 1 point 3 points For the correct application of the loop theorem to an appropriate loop of the circuit For example, using the right-hand loop containing L and R2 VR2 + VL = 0 1 point VR2 = R2 I init VL = - L dI dt dI dt This equation could also be obtained directly by recognizing that L and R2 are in parallel and have the same voltage across them. For the correct substitution of the current obtained in part (a) dI e = R2 L dt R1 + R2 For the correct answer R2 e dI = dt ( R1 + R2 ) L R2 I init = L 1 point 1 point Copyright © 2005 by College Entrance Examination Board. All righ...
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