Sp06-Final-Smoot-Soln1

Sp06-Final-Smoot-Soln1 - Draft Solutions Smoot Spring 2006...

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Draft Solutions: Smoot Spring 2006 1. [41 points] Short Questions (a) [15 points] Circle T or F for True or False T F (i) An induced EMF is produced by a changing magnetic ﬁeld. T F (ii) An induced EMF gives rise to a current whose magnetic ﬁeld opposes the original change in ﬂux. T F (iii) An EMF is induced in a conductor moving in a magnetic ﬁeld. this is true for a general ﬁeld but not when ~ B is parallel to ~v T F (iv) An electric generator using the Faraday eﬀect is a DC generator. A dynamo is an AC generator. T F (v) Because of Lenz’s law, there is always a back or couter EMF and a counter torque. There are also eddy currents. if no competed circuits, there are no currents and thus no back or counter EMF, torque or eddy currents. T F (vi) A transformer is either a step-up transformer or a step-down transformer. a transformer with ratio of turns unity is possible and usually called an isolator as it does not actually transform the voltage or current. T F (vii) The general form of Faraday’s Law states that a changing magnetic ﬂux produces an electric ﬁeld around the magnetic ﬂux. T F (viii) The forces produced by a changing magnetic ﬁeld are conservative. T F (ix) Mutual inductance between two circuits is symmetric and equal and due to the linkage of magnetic ﬂux between the two circuits. T F (x) Self-inductance is the coupling of a circuit to itself as a result of the coupling of its magnetic ﬂux. T F (xi) There is both energy and pressure stored in a magnetic ﬁeld. T F (xii) An LR (inductance and resistance) circuit has a characteristic time of L/R . T F (xiii) An LC (inductance and capacitance) circuit has a characteristic angular frequency of p 1 /LC T F (xiv) An LRC circuit has both a characteristic frequency p 1 /LC and damping time of 65

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2 L/R . the frequency is oﬀset by the resistance. T F (xiv) In AC circuits the AC voltages and AC currents have the same frequency. T F (xvi) An AC current going through an inductor lags the voltage across the inductor by 90 . T F (xvii) The AC charge on a capacitor precedes the voltage across the capacitor by 90 . T F (xviii) Maxwell’s equations gives the relationship between the electric and magnetic ﬁelds and their corresponding charges and currents. T F (xix) Maxwell’s equations predicted electromagnetic waves. That is the wave equation can be derived from Maxwell’s equations. T F (xx) Electromagnetic waves carry momentum and produce pressure. T F (xxi) The linkage of magnetic ﬂux from circuit A to circuit B is the same as the linkage of magnetic ﬂux from circuit B to circuit A. T F (xxii) All materials are diamagnetic. The diamagnetism is sometimes over ridden by ferromagnetism or paramagnetism. T
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This note was uploaded on 02/09/2010 for the course PHYSICS 7B taught by Professor Packard during the Spring '08 term at Berkeley.

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Sp06-Final-Smoot-Soln1 - Draft Solutions Smoot Spring 2006...

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