# final_2006_answer - Physics 213 Practice Final Fall 2007...

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Physics 213 Practice Final Fall 2007 page 1 of 13 ANSWER KEY

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Physics 213 Practice Final Fall 2007 page 2 of 13 1. True/False [10 points] Indicate T (True) or F (False) in the space at left for each of the following statements. __F__ An appropriate unit for impedance is Ohm- second (Ω -s). __T__ The magnetic forces between the adjacent coils of a solenoid act to decrease the solenoid length and increase its radius. __F__ The integral of   B d  A over a closed surface, in the case of a uniform magnetic field, is equal to the total surface area times the magnetic field magnitude. _T___ A charged particle subject only to magnetic forces has constant kinetic energy. __F__ To cause a time-varying magnetic flux through a circular loop confined to a region with a uniform magnetic field   B , you can move the loop in a direction perpendicular to   B . __T __ A bar magnet dropped into the top of a vertical aluminum tube will be emerge from the tube’s bottom more slowly than a non-magnetic bar dropped through the tube. __F__ The asymptotic current in an R-L circuit powered by an ideal battery with emf E depends on the values of all of R, L and E . __T__ The ratio of units [E]/[B] is “meters / second” in the MKS system. __T__ In an AC circuit, a capacitor is effectively "invisible" at very high frequency, i.e. virtually indistinguishable from an ideal conductor. __F__ The peak power in an AC circuit is given by the average power multiplied by 2 .
Physics 213 Practice Final Fall 2007 page 3 of 13 2. [3 points] A conductor has electrons as the charge carrier of electric current. You place the conductor in a region containing a uniform magnetic field in the positive z direction (   B B ˆ k , out of page). If you run an electric current in the positive x direction (   J J ˆ i ) through your conductor, then a Hall effect voltage difference would result from an electric field in what direction? 1. +x direction 2. x direction 3. +y direction 4. y direction 5. +z direction (out of page) 6. z direction (into page) Answer: ____4__________ 3. [3 points] Equal electric currents I flow in opposite directions in wires that pass through the plane of this page. For the path in the plane of this page shown at right, what is the value of B dl around the path? 1. 2μ 0 I 2. μ 0 I 3. 0 4. μ 0 I 5. 0 I Answer: _____4_________

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Physics 213 Practice Final Fall 2007 page 4 of 13 4. [7 points] An ideal battery with an emf E is connected to the circuit shown at right. Suppose that the top switch has been closed for a very long time. A) (3 points) What is the value of the current (
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## This note was uploaded on 08/27/2009 for the course PHYS 2213 taught by Professor Perelstein,m during the Fall '07 term at Cornell University (Engineering School).

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final_2006_answer - Physics 213 Practice Final Fall 2007...

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