Ch 32 Relevant Concept Questions

Ch 32 Relevant Concept Questions - magnetic field magnitude...

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University Physics Young and Freedman Chapter 32 Concept Questions and solutions Chapter 32: Pre-Chapter Question Q: Why do cellular phones sometimes have poor reception inside steel-frame office buildings? A: Electromagnetic waves arriving from outside the building cannot propagate into conductors like steel. Instead, the wave is reflected back outside, so less wave energy reaches the phone and the reception is compromised. 1. Is it possible to have a purely electric wave propagate through empty space—that is, a wave made up of an electric field but no magnetic field? What a bout a purely magnetic wave? Ampere's law says no for the first one. Faradays' says no for the second. 2. In a wave of the sort depicted in Fig. 32.3, the magnitude of the electric field behind the wave front is 4.50 x 10^2 V/m. What is the magnitude of the magnetic field? B = 1.50 x 10^-6 T. Because c in m/s is so big, the
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Unformatted text preview: magnetic field magnitude in T is much smaller than the electric field in V/m. See page 1264 for clarification. 3. A sinusoidal electromagnetic wave is traveling in the negative z-direction. What are the possible wave functions for the electric and magnetic fields if the wave is linearly polarized in the x-direction? See page 1264 4. Fig. 32.10 shows one wavelength of a sinusoidal electromagnetic wave at time t = 0. For which values of x between x = 0 and x = λ is the energy density at a maximum? For which values is it at a minimum? For which values of x is the magnitude of the instantaneous (not average) Poynting vector at a maximum? For which values is it at a minimum? Both the energy density u and the Poynting vector magnitude S are max where the electric and magnetic fields have their max magnitudes. This occurs at x = λ/4 & 3λ/4....
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This note was uploaded on 04/18/2008 for the course PHYS 0030 taught by Professor Cutts during the Spring '07 term at Brown.

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