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Unformatted text preview: Husain, Zeena Homework 13 Due: Apr 27 2004, 4:00 am Inst: Sonia Paban 1 This printout should have 22 questions. Multiplechoice questions may continue on the next column or page find all choices before making your selection. The due time is Central time. 001 (part 1 of 2) 10 points To demonstrate the generation of electromag netic waves due to oscillations of a current sheet in the yzplane at x = 0, one first con siders the following situation. One turns on a steady current flow along the negative yaxis at t = 0. p z I x y The point P is along the negative x direction. Let ~ B and ~ E be the magnetic and electric field established at P soon after the switching on of the current, respectively. The directions of ~ B and ~ E are 1. ~ B is along the positive zaxis, ~ E is along the negative yaxis. 2. ~ B is along the negative yaxis, ~ E is along the positive zaxis. 3. ~ B is along the negative yaxis, ~ E is along the negative zaxis. 4. ~ B is along the negative zaxis, ~ E is along the negative yaxis. 5. ~ B is along the positive yaxis, ~ E is along the positive zaxis. 6. ~ B is along the positive zaxis, ~ E is along the positive yaxis. 7. ~ B is along the negative zaxis, ~ E is along the positive yaxis. correct 8. ~ B is along the negative zaxis, ~ E is along the positive zaxis. 9. ~ B is along the negative yaxis, ~ E is along the positive yaxis. 10. ~ B is along the positive yaxis, ~ E is along the negative zaxis. Explanation: Basic Concepts Electromagnetic waves. Since the current on the sheet is flowing along the negative yaxis, the magnetic field for neg ative values of x is directed along the negative zaxis. x y O O z P P E E B B B A C D About point P we may construct a rectan gular window ABCDA in the xyplane. As the front of the Bfield sweeps across the window to the left, it causes a counterclock wise induced emf, which is generated by the induced emf at the right side of the window from D to A . Since the side DA can be placed at any location between O and P , when the Bfield reaches P , there is a companion E field stretched out from D to A . Notice that the electromagnetic wave is traveling along the negative xaxis, so ~ E has to be directed along the positive yaxis (so that ~ E ~ B is directed along the correct direction). Husain, Zeena Homework 13 Due: Apr 27 2004, 4:00 am Inst: Sonia Paban 2 002 (part 2 of 2) 10 points Now consider the current sheet which under goes the sinusoidal oscillations with a definite frequency where the amplitude of the mag netic field oscillations in the waves is B max . Consider a book of area A located at P paral lel to the yz plane. Find the radiation force on the book, if it absorbs one third of the light....
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This note was uploaded on 10/13/2009 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
 Spring '08
 Turner
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