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Unformatted text preview: lim (kl9356) Homework 20 Weathers (22202) 1 This printout should have 16 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points The magnetic field amplitude of an electro magnetic wave is 9 . 1 10 6 T. The speed of light is 2 . 99792 10 8 m / s . Calculate the amplitude of the electric field if the wave is traveling in free space. Correct answer: 2728 . 11 N / C. Explanation: Let : c = 2 . 99792 10 8 m / sand B = 9 . 1 10 6 T . According to Maxwells equations for an elec tromagnetic wave in vacuum the relation be tween the amplitude of the magnetic field and the amplitude of the electric field must be E = c B = (2 . 99792 10 8 m / s) (9 . 1 10 6 T) = 2728 . 11 N / C . The same relation applies even when the ve locity of light in the medium is not c , in general, E = v B , where v is the velocity of light in that medium. 002 10.0 points Gammaray bursters are objects in the uni verse that emit pulses of gamma rays with high energies. The frequency of the most en ergetic bursts has been measured at around 3 . 10 21 Hz. The speed of light is 3 10 8 m / s. What is the wavelength of these gamma rays? Correct answer: 1 10 13 m. Explanation: Let : f = 3 . 10 21 Hz and c = 3 . 00 10 8 m / s . The speed is c = f = c f = 3 10 8 m / s 3 10 21 Hz = 1 10 13 m . 003 (part 1 of 4) 10.0 points A cylindrical filament has radius 2 . 96 mm. Its resistance is 3 . 39 and its length is 0 . 45 m. The filament carries a uniform, steady current of 0 . 829 A. The permeability of free space is 4 10 7 N / A 2 . Find the electric field inside the filament. Correct answer: 6 . 24513 N / C. Explanation: Let : = 0 . 45 m , R = 3 . 39 , and I = 0 . 829 A . The electric field inside the filament has to point in the direction of the current; the field causes the current to flow. To find the field, first consider the voltage drop across the ends of the wire, V = I R . The electric field inside the filament is E = V = I R = (3 . 39 ) (0 . 829 A) . 45 m = 6 . 24513 N / C . 004 (part 2 of 4) 10.0 points Find B at the surface of the filament....
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This note was uploaded on 09/07/2010 for the course PHYS 2220 taught by Professor Littler during the Spring '00 term at North Texas.
 Spring '00
 Littler
 Magnetism, Work

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