su09EIII - Physics 54 Summer 2009 Exam III Solutions In...

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Physics 54 Summer 2009 1 Exam III Solutions In questions or problems not requiring numerical answers, express the answers in terms of the symbols given, and standard constants. If numbers are required, use g = 10 , k = 1/ 4 !" 0 = 9 # 10 9 and μ 0 = 4 ! " 10 # 7 (all in SI units). Part A: Multiple choice questions, 4 points each. Check the best answer. 1. A series circuit has an AC generator, a light bulb (resistor), an inductor and a capacitor. Measurement shows that the rms voltage across the capacitor is larger than that across the inductor. To make the light bulb glow brighter, one can: Decrease the frequency of the generator. [Increases X C , decreases X L ] Decrease the capacitance. [Increases X C ] Decrease the inductance. [Decreases X L ] All of the above will make the bulb glow less brightly. 2. The capacitor shown has charge Q as indicated, which is decreasing . At point P near the edge of the capacitor plates, which of the following is NOT true? The E-field lines run from left to right. The Poynting vector is upward. The B-field is directed into the page. The current runs to the right. [Left, decreasing charge] + Q P
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Physics 54 Summer 2009 2 3. Which is NOT true of the light from the sun that we see when we look at the sky on a clear day? The blue color arises from the ! 4 dependence of the scattered intensity. The skylight is preferentially polarized with E perpendicular to the plane containing the incident and scattered rays. The degree of polarization of the skylight is the same no matter in what direction we look. [Maximum when ray from sun and scattered ray are perpendicular] The reddish color of direct sunlight at sunset arises because of the 4 dependence of the scattered intensity.
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su09EIII - Physics 54 Summer 2009 Exam III Solutions In...

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