PHY2049_20100402143031_Exam 3 Problems

# PHY2049_20100402143031_Exam 3 Problems - Generated by Foxit...

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1 PHY 2049: Chapter 30-33 Problems Notes on these problems: § The problems all come from old tests. § Answer choice #1 is the correct answer to every problem. § Detailed solutions will be posted online at &Itemid=9 § The equation sheet you will be given for the test will be posted on your course website, so be sure to have a look at it before the test. § The equations you actually need are shown in the review, so you should make sure you know all of them, not just the ones on the equation sheet. Chapter 30 Problems (1) Lenz’s law The current in the large loop is in the clockwise [or counterclockwise] direction and increasing. What is the direction of the induced current in loop 2 and in loop 3, respectively? (1) clockwise, clockwise (2) clockwise, counterclockwise (3) counterclockwise, clockwise (4) counterclockwise, counterclockwise (5) no induced current (2) Lenz’s law Consider the arrangement shown in the figure. A conducting rod, PQ, is lying on a U- shaped conducting wire, making good electrical contact with it, and both are supported on a nonconducting table. There is a uniform magnetic field pointing into the table. If the magnetic field strength is decreased, which way does the rod move? (1) right (2) left (3) up along the page (4) down along the page (5) does not move 1 2 3 Q P Generated by Foxit PDF Creator © Foxit Software http://www.foxitsoftware.com For evaluation only.

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2 (3) Magnetic flux Assume the average value of the vertical component of Earth’s magnetic field is 63μT (downward) in some region, which has an area of 3.19×10 5 km 2 , and calculate the net magnetic flux (in Webers) through the rest of Earth’s surface (the entire surface excluding that region). Take the negative direction to be inward. (1) 2.0×10 7 (2) 2.4×10 9 (2) 1.9×10 4 (2) 3.6×10 5 (2) 3.0×10 4 (4) Induced emf An elastic conducting material is stretched into a circular loop of 15.0cm radius. It is placed with its plane perpendicular to a uniform 0.500T magnetic field. When released, the radius of the loop starts to shrink at an instantaneous rate of 78.0cm/s. What emf, in volts, is induced in the loop at that instant? (1) 0.37 (2) 0.74 (3) 1.23 (4) 0.11 (5) 0.23 (5) Induced emf of a rectangular loop A metal rod is forced to move with constant velocity of 60cm/s along two parallel metal rails, which are connected by metal at one end (see figure). The rails are separated by 20cm, and there is a magnetic field of 2T coming out of the page. If the rod has resistance 50Ω and the rails and connector have negligible resistance, what force (in N) is required to keep the rod moving at constant velocity? (1) 1.9×10
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## This note was uploaded on 05/17/2011 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.

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PHY2049_20100402143031_Exam 3 Problems - Generated by Foxit...

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