Phy122_0923

# Phy122_0923 - Physics 122 Sept 23 2010 Starting chapter 18...

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Unformatted text preview: Physics 122 Sept. 23, 2010 Starting chapter 18. This lecture and the one on September 28 th are the end of the material that will appear on your 1 st midterm exam. ectures on Chapter 19 (magnetism) will be Lectures on Chapter 19 (magnetism) will be September 30 and October 5, before the midterm. The chapter 19 homework set will be due October 6 th , one day after the midterm. Budget your time! Question 1: Question 2: light bulb consists of a thin tungsten wire which is A light bulb consists of a thin tungsten wire, which is heated to incandescence by the current flowing through it. As the bulb ages, some of the tungsten evaporates, making the wire thinner. Does this make the bulb burn brighter (more power) or dimmer (less power)? Hint: Is the bulb connected to a source of constant voltage, or constant current? Question 2: light bulb consists of a thin tungsten wire which is A light bulb consists of a thin tungsten wire, which is heated to incandescence by the current flowing through it. As the bulb ages, some of the tungsten evaporates, making the wire thinner. Does this make the bulb burn brighter (more power) or dimmer (less power)? Hint: Is the bulb connected to a source of constant voltage, or constant current? Resistance of the wire, R = ρ l / A . As the material evaporates, A gets smaller (other terms remain the same) so R gets larger. lectrical circuit provides constant voltage so the Electrical circuit provides constant voltage V , so the power, V 2 / R gets smaller. Bulb grows dimmer. Question 3: he settings on the oscilloscope that recorded this signal The settings on the oscilloscope that recorded this signal were 10 ms/div horizontal and 0.5 V/div vertical....
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Phy122_0923 - Physics 122 Sept 23 2010 Starting chapter 18...

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