Finally, the switch on the electromagnet is reopened. The magnitude of the external magnetic flux through the wire loop ______ (A. increases, B. decreases, C. remains constant), and there is _______ (A. zero, B. a clockwise, C. a counterclockwise) current induced in the loop (as seen from the left).Enter the letters corresponding to the responses that correctly complete the statement above. For example, if the correct answers are A and C, type A,C
Question
Finally, the switch on the electromagnet is reopened. The magnitude of the external magnetic flux through the wire loop ______ (A. increases, B. decreases, C. remains constant), and there is _______ (A. zero, B. a clockwise, C. a counterclockwise) current induced in the loop (as seen from the left).Enter the letters corresponding to the responses that correctly complete the statement above. For example, if the correct answers are A and C, type A,C
Solution
To answer this question, we need to understand Faraday's Law of electromagnetic induction. According to Faraday's Law, an electromotive force (and hence current) is induced in a loop when there is a change in magnetic flux through the loop.
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When the switch on the electromagnet is reopened, the magnetic field created by the electromagnet decreases. This means that the external magnetic flux through the wire loop also decreases. So, the correct answer to the first blank is B. decreases.
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According to Lenz's Law, which is a consequence of the law of conservation of energy, the induced current will always work to oppose the change in magnetic flux that produced it. In this case, since the magnetic flux is decreasing, the induced current will act in such a way as to try to keep the flux from decreasing. This means it will create its own magnetic field in the same direction as the original magnetic field. If we are looking from the left, this would appear as a counterclockwise current. So, the correct answer to the second blank is C. a counterclockwise.
So, the correct answers are B, C.
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