Exam2_nosolutions

# Exam2_nosolutions - Final Exam: Graduate Electromagnetics...

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Final Exam: Graduate Electromagnetics I, 95.657 Fall 2008, UMass Lowell, Dr. Baird Part I: Multiple Choice (60 Points) Circle only one answer to each question. In this section, you should be able to determine which answer is correct using only physical argument and an understanding of the equations. No mathematical calculations are necessary to answer any of the multiple choice questions. 1. What type of magnetic field H exists in a magnetostatics system that has no free currents? (a) a curl-less (irrotational) magnetic field H (b) a curling (rotational) magnetic field H (c) a zero magnetic field H (d) an oscillating magnetic field H 2. The surface of a sphere is covered uniformly with a fixed electric charge and the sphere is spun about its diameter at a constant frequency. What type of magnetic field does it generate? (a) no magnetic field (b) a monopole magnetic field (c) a dipole magnetic field (d) a quadrupole magnetic field 3. What type of external magnetic field repels a small magnetic dipole? (a) none, magnetic dipoles are never repelled (b) a uniform magnetic field (c) a very strong uniform magnetic field (d) a non-uniform magnetic field with regions of high flux density 4. What gives rise to diverging electric fields? (a) magnetic monopoles (b) magnetic dipoles (c) magnetic charges (d) electric charges 5. What is the relationship between the potential energy U of a test charge in a static electric field and the electric scalar potential Φ ? (a) the potential energy is proportional to electric scalar potential differences (b) there are the exact same thing (c) they are not related at all (d) they are related by an inverse square law 6. A small round plate of electric charge sits in a region of free space with no boundaries. What equation would be used to find the exact electric potential everywhere? (a) Coulomb's law: (b) the Laplace equation: (c) the Green function solution: (d) the first few terms of the multipole expansion:

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7. A small round plate of electric charge is suspended in the middle of a hollow grounded metallic sphere. What equation would be used to find the exact electric potential inside the sphere? (a) Coulomb's law (b) the Laplace equation (c) the Green function solution (d) the first few terms of the multipole expansion 8. Consider a point charge + q at the location ( x = a , y = a ), a point charge - q at the location ( x = -a, y = a ) and an semi-infinite grounded conducting plate defined by the x - z plane. If we used the method of images to solve for the electric potential, where should we place the image charge(s)? (a) put a charge + q at ( x = 0 , y = - a ) (b) put a charge +2 q at ( x = 0 , y = - a ) (c) no image charges required because the total charge is zero (d) put a charge - q at ( x = -a , y = - a ) and a charge + q at ( x = a , y = - a ) 9. Far away ( r >> a ) from the system in the previous problem, how does the electric potential depend on the distance r ? (a)
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## This note was uploaded on 03/21/2012 for the course PHY 2030 taught by Professor Avery during the Spring '11 term at University of Florida.

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Exam2_nosolutions - Final Exam: Graduate Electromagnetics...

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