PastHourExamII(03-26-07)

# PastHourExamII(03-26-07) - Department of Physics Lehigh...

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1 Department of Physics, Lehigh University Physics 21 – Introductory Physics II Spring 2007 Hour Exam II April 3, 2007 Closed Notes 9:20 AM-10:10 AM Student’s Name______________________ Recitation Section Number______________ Recitation Leader’s Name_______________ The test is a multiple-choice examination. First, check to be sure that you have a six- page examination, including the equation sheet. Please answer each question by circling one answer from the panel of choices available within each question space. 1. A long solenoid consists of N uniform turns of conducting wire, each turn with radius R, as shown in the figure. We are interested in evaluating the line integral of B d l along the closed rectangular loop that includes five turns of the wire, going from a to b to c to d to a, as shown by dotted lines in the figure. The lengths of the sides of the loop are l and r , respectively. Here B is the magnitude vector of the magnetic induction at a point in space, and d l designates a differential element of displacement along the path. A. The value of the closed-loop line integral, a-b-c-d-a , is: i) 2 B l ; ii) B (l + r) ; iii) 2 B r; iv) B l ; or v) B l r . B. We are interested in finding the magnitude of the B -field. Which of the following principles can be used to solve this problem? Circle all that applies. i) Faraday’s law; ii) Ampere’s law; iii) Biot-Savart law; iv) Coulomb’s law C. Now the conducting wire has a constant electric current I . The value of the B -field inside the solenoid is: i) l I o ε ; ii) l I o 5 μ ; iii) () r l I o + ; or iv) r l I o + D. The interior space of the solenoid is filled with a close-fitting rod of iron, which has a magnetic permeability . The strength of the B -field is now: i) Much greater; ii) Unchanged; iii) Smaller than before; or iv) Slightly greater.

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PastHourExamII(03-26-07) - Department of Physics Lehigh...

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