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Unformatted text preview: song (shs546) Practice HW 20 Solutions weathers (22202) 1 This printout should have 12 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 0.0 points The electric field between the plates of an air capacitor of plate area 0 . 33 m 2 is changing at a rate of 37800 V / m / s. The permitivity of free space is 8 . 85419 10 12 C 2 / N / m 2 . What is Maxwells displacement current? Correct answer: 1 . 10447 10 7 A. Explanation: Let : = 8 . 85419 10 12 C 2 / N / m 2 , A = 0 . 33 m 2 , and d E dt = 37800 V / m / s , where A is the area and d E dt is the changing rate of the electric field. The displacement current is I D = A d E dt = ( 8 . 85419 10 12 C 2 / N / m 2 ) ( . 33 m 2 ) (37800 V / m / s) = 1 . 10447 10 7 A . 002 0.0 points The electric field in an electromagnetic wave (in vacuum) is described by E = E max sin( k x t ) , where E max = 8 . 6 N / C and k = 9 . 7 10 8 m 1 . The speed of light is 2 . 99792 10 8 m / s. Find the amplitude of the corresponding magnetic wave. Correct answer: 2 . 86865 10 8 T. Explanation: Let : c = 2 . 99792 10 8 m / s and E max = 8 . 6 N / C . The relation between the magnitude of the electric field and that of the magnetic field for an electromagnetic wave is given by B = E c . Thus, the magnitude of the magnetic wave is B max = E max c = 8 . 6 N / C 2 . 99792 10 8 m / s = 2 . 86865 10 8 T . 003 (part 1 of 2) 0.0 points What is the wavelength corresponding to a frequency of 9 10 19 Hz of electromagnetic wave in free space? The speed of light is 2 . 99792 10 8 m / s. Correct answer: 3 . 33103 10 12 m. Explanation: Let : f = 9 10 19 Hz and c = 2 . 99792 10 8 m / s . The relation between frequency and wave length is given by = c f = 2 . 99792 10 8 m / s 9 10 19 Hz = 3 . 33103 10 12 m ....
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 Spring '00
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