# hw10 - e What is the advantage of using an inductor instead...

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HOMEWORK FOR WEEK 10: DUE THU APRIL 14 IN CLASS 1) An efficient way of making a light dimmer is to place a variable inductor in series with a light bulb. We’ll think of the light bulb as an ideal resistor with R=100 Ω . The inductor has no resistance and L can be varied from 0 to L max . The electrical supply is 120V (rms) at 60Hz. a) What setting for L will maximize the power dissipated in the light bulb? b) What is this maximum power? c) The minimum power is 10% of the maximum power. What is L max ? d) The inductor could be replaced by a resistor to achieve the same reduction in the power dissipated in the light bulb. What resistor would be required?
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Unformatted text preview: e) What is the advantage of using an inductor instead of the resistor? 2) A parallel plate capacitor of capacitance C has circular plates of radius r. A concentric circular loop of radius r/2 is between the circular plates. For t<0 the capacitor has charge Q. At time t=0 the capacitor is connected to a resistor R. a) What is the initial rate value of dV/dt just after the switch is closed? b) What is the total displacement current through the circular loop just after the switch is closed? c) What is the magnetic field magnitude at points on the circular loop just after the switch is closed? R L 120V r r/2 R Q...
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