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Unformatted text preview: Solution for Homework 16 Magnetic Force and Field Solution to Homework Problem 16.1(Opposites Attract) Problem: A proton with charge (+ e ) is fixed at the origin. An electron with charge (- e ) is fixed at the point (1cm , , 0) . What is the direction of the total force on the electron? Select One of the Following: (a) + y . (b)- y (c) + x (d-Answer)- x Solution Opposites attract so,- x Total Points for Problem: 3 Points Solution to Homework Problem 16.2(Motion of Moment in Field) Problem: An object with a magnetic moment is placed in a uniform magnetic field such that the magnetic moment is not aligned with the field. Which of the following happens? Select One of the Following: (a) Nothing. (b-Answer) The object rotates. (c) The objects center moves. (d) The object rotates and its center moves. Solution (b): If the external magnetic field is truly uniform, then no translation will occur. The moment will rotate until it is aligned with the external field, but if there is no loss of energy (ie, friction) the moment will rotate past equilibrium, slow down, stop, then rotate back toward equilibrium, and oscillate indefinitely. If there is friction in the system, the magnetic moment will eventually align itself with the external field, and its motion will cease. Total Points for Problem: 3 Points Solution to Homework Problem 16.3(Declination Angles at Various Places) Problem: A dip needle is a small magnet mounted on a horizontal axis so that it can swivel up or down (like a compass turned on its side). (a)Where on the earth will a dip needle point most nearly vertically? Select One of the Following: 1 (a) The equator (b-Answer) The North or South Pole. (b)Where will it point most nearly horizontally? Select One of the Following: (a-Answer) The equator (b) The North or South Pole. Solution to Part (a) The earths field is nearly vertical at the North and South Pole. Grading Key: Solution to Part (a) 2 Points Solution to Part (b) Earths field is horizontal at the equator....
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