Final_Exam - Final Exam: Graduate Electromagnetics I,...

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Final Exam: Graduate Electromagnetics I, 95.657 Fall 2011, UMass Lowell, Dr. Baird Part I: Multiple Choice (30 Points) Circle only one answer to each question. In cases where many answers may seem true, choose the one best answer. 1. The current I runs through an arbitrarily-shaped loop of thin wire. How does the magnetic field strength B produced by this system depend on I ? (a) B is proportional to I 2 (b) B is proportional to I (c) B does not depend on I (d) B is proportional to cos( I ) 2. An electric charge distribution is given by: ρ= Q 4 π R 3 sin ( 5 r R ) e ( r R ) 2 cos 3 θ where R is some constant radius, Q is some constant charge, r is the radial dimension of spherical coordinates and θ is the polar angle of spherical coordinates. If we were to solve for the electrostatic potential created by this charge distribution, what kind of functions would the final solution involve? (a) complex exponentials (b) Bessel functions (c) ordinary Legendre polynomials (d) spherical harmonics 3. In magnetostatics, which one of the potential definitions is valid, B =∇× A or B =−∇ Ψ M ? (a) only B =∇× A (b) only B =−∇ Ψ M (c) Both B =∇× A and B =−∇ Ψ M are valid all the time (d) B =∇× A is valid all the time, but B =−∇ Ψ M is only valid when there is no total current 4. Which expression describes electromagnetic field energy flow ? (a) ½( E D + B H ) (b) E × H (c) E × D (d) J E 5. What does the surface of a diamagnetic material tend to do to a pre-existing external magnetic field? (a) nothing (b) repels and dilutes magnetic field lines (c) attracts and concentrates magnetic field lines (d) knots up the field lines
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6. When we solved for the potential of a point charge outside a conducting sphere using the method of images, where did we place the image charge(s)? (a) one image charge was placed in the sphere on the line connecting the real charge with the sphere's
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Final_Exam - Final Exam: Graduate Electromagnetics I,...

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