online assignment 7-1-1

# online assignment 7-1-1 - MasteringPhysics: Assignment...

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Manage this Assignment: 6a. Induction Due: 11:00pm on Sunday, February 14, 2010 Note: To understand how points are awarded, read your instructor's Grading Policy . Print Version with Answers Understanding Changing Flux Description: Lenz's law problem that illustrates the relationship between changing flux and induced current using the example of an electromagnet near a loop of wire. In this problem, you will use Lenz's law to explore what happens when an electromagnet is activated a short distance from a wire loop. You will need to use the right-hand rule to find the direction of the induced current. Consider the arrangement shown in the figure. Part A When the switch is open, which of the following statements about the magnetic flux through the wire loop is true? Assume that the direction of the vector area of the wire loop is to the right. When the switch is open, there is no current flowing in the circuit. Thus, the electromagnet does not produce a magnetic field, and the flux is zero. ANSWER: There is no magnetic flux through the wire loop. There is a positive flux through the wire loop. There is a negative flux through the wire loop. Part B What is the direction of the induced current in the wire loop (as seen from the left) when the switch is open? ANSWER: There is no induced current. Page 1 of 16 MasteringPhysics: Assignment Print View 2/12/2010 http://session.masteringphysics.com/myct/assignmentPrint?assignmentID=1350227

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The induced current is clockwise. The induced current is counterclockwise. Part C Now the switch on the electromagnet is closed. What is the direction of the induced current in the wire loop immediately after the switch is closed (as seen from the left)? Hint C.1 How to approach the problem When the switch is open, the magnetic field produced by the electromagnet is zero. When the switch is closed, a current flows through the coil of the electromagnet, and a magnetic field is produced. Determine how this field changes the flux through the wire loop. Then use Lenz's law to determine the direction of the induced current. Hint C.2 The field produced by the electromagnet The current flows from the positive battery terminal to the negative one. Therefore, when the switch is closed, the current in the electromagnet is clockwise as seen from the left. The figure shows some of the magnetic field lines produced by the electromagnet. Hint C.3 Apply Lenz's law Lenz's law states that the current induced in the wire loop has the direction such that the magnetic flux created by the current opposes the change in the external magnetic flux that caused the current. Use the right-hand rule to find the direction of the induced current that would generate a field opposing the
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## This note was uploaded on 07/01/2010 for the course PHYS 101213 taught by Professor Bratton during the Spring '10 term at CSU Chico.

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online assignment 7-1-1 - MasteringPhysics: Assignment...

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