Exam 3.1.pdf - Version 043 Midterm 03 yao(56125 1 This...

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Version 043 – Midterm 03 – yao – (56125) 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 The figure represents two long, straight, par- allel wires carrying equal currents extending in a direction perpendicular to the page. The current in the right wire runs into the page and the current in the left runs out of the page. Pivot i What will happen to the magnet if its orig- inal orientation is as shown in the figure, with the current coming in on the front side of the solenoid, and then looping around the back? a b c What is the direction of the magnetic field created by these wires at location a, b and c? (b is midway between the wires.) 1. down, up, down correct 2. up, zero, down 3. down, zero, up N S
4. down, zero, down A single piece of wire is bent into the shape of Texas, with a total area of 3 . 08 cm 2 . This Texas shaped loop is perpendicular to a mag- netic field which increases uniformly in mag- nitude from 0 . 889 T to 1 . 85 T in a time of 2 s. The wire has a total resistance of 3 Ω. What is the current? 10.0points 003 10.0points Correct answer: 0 . 0493313 mA. This study resource was shared via CourseHero.com
An electric current runs through a coil of wire as shown. A permanent magnet is located to the right of the coil. The magnet is free to rotate. Explanation: BasicConcepts: Faraday’s Law of Induc-
Version 043 – Midterm 03 – yao – (56125) 2 tion: E = d Φ B dt The particular shape of the wire is unimpor- tant, only the area enclosed by the wire mat- ters. The magnetic flux through the loop is given by Φ = B A . d Φ dt = d dt ( B A ) = A d B dt = A Δ B Δ t = A B 2 B 1 Δ t = (0 . 000308 m 2 )(0 . 4805 T / s) = 0 . 000147994 V . From Faraday’s Law: E = d Φ dt = 0 . 000147994 V From Ohm’s Law: I = E R = 0 . 000147994 V 3 Ω = 0 . 0493313 mA 004 10.0points Two parallel wires carry opposite current as shown. i 1 i 2 Find the direction of the magnetic force on i 2 due to the magnetic field of i 1 . 1. to the right and downward 2. out of the paper 3. to the left and downward 4. to the right correct 5. to the left 6. to the right and upward 7. into the paper 8. to the left and upward Explanation: i 1 i 2 F 2 B 1 Wire 1, which carries a current i 1 , sets up a magnetic field vector B 1 , which points into the paper at the position of wire 2. The direction of vector B 1 is perpendicular to the wire, as illustrated below. The magnetic force on a length l of wire 2 is vector F 2 = i 2 vector l × vector B 1 . Since i 2 flows downward, vector l × vector B 1 is to the right.

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