Practice Midterm 03-solutions - nguyen(ktn529 Practice...

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nguyen (ktn529) – Practice Midterm 03 – yao – (56120) 1 This print-out should have 18 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0points A 1 . 11 H inductor carries a steady current of 0 . 547 A. When the voltage source in the circuit is shorted out, the current disappears in 15 . 1 ms. What is the average induced emf in the inductor during this time? L = 0 . 486 m , B = 0 . 000192 T , and μ 0 = 4 π × 10 7 T · m / A . The magnetic field inside a long solenoid is parenleftbigg N L parenrightbigg 003 10.0points Use Lenz’s law to answer the following ques- tion concerning the direction of induced cur- rents. v S N
| ε | = L Δ I Δ t = (1 . 11 H) 0 . 547 A 0 . 0151 s = 40 . 2099 V . 002 10.0points What current is required in the windings of a long solenoid that has 2100 turns uni- formly distributed over a length of 0 . 486 m in order to produce a magnetic field of magnitude 0 . 000192 T at the center of the solenoid? The permeability of free space is 4 π × 10 7 T · m / A . R a b We introduce the following notations: A) The direction of the induced magnetic field within the solenoid is A1 : to the left A2 : to the right A3 : upward A4 : downward A5 : into the paper B) The direction of the induced current through the resistor R is B1 : from a through R to b B2 : from b through R to a What is correct when the bar magnet is moved
to the left?
nguyen (ktn529) – Practice Midterm 03 – yao – (56120) 2 2. A2, B2
004 10.0points In the arrangement shown in the figure, the resistor is 8 Ω and a 9 T magnetic field is directed into the paper. The separation between the rails is 7 m . An applied force moves the bar to the right at a constant speed of 2 m / s . m 1 g 2 m / s 8 Ω 9 T 9 T I 7 m Calculate the applied force required to move the bar to the right at a constant speed of 2 m / s . Assume the bar and rails have negli- gible resistance and friction. Neglect the mass of the bar.

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