Physics 8: Homework 6 Additional Questions



In addition to the problems from the book (13.E.19, 13.E.21, 13.E.22, 13.E.24, 13.E.25, 13.E.26), here are more problems that are a required part of the assignment:

  1. Draw an AM signal conveying a triangle wave sound waveform:
  2. Draw an FM signal conveying a square wave sound waveform:
  3. Radios and cell phones usually don't work well in elevators. Why might this be true? (This is most definitely connected with a topic covered in lecture.)
  4. Estimate how long it will take to boil a mug of water in a microwave rated at 1000 W. Use the heat capacity of water (can use rounded, imprecise version) and make estimates for the volume/mass of water, and starting and ending temperatures. It may help to know that the density of water is 1 kg per liter, and that a liter is approximately the same as a quart—which is 32 ounces. Assume that all of the microwave's power is absorbed by the water.
  5. Two hot dog franks cooked in boiling water take just as long to cook as a single frank would in the same water. But in a microwave, it takes double the time to cook two vs. one. Why?
  6. The TV channel 2 and channel 13 carrier frequencies are at 55.25 MHz and 211.25 MHz, respectively. If these signals are emitted from a horizontal antenna (horizontal polarization), how long should you adjust your TV antenna to be, and in what orientation to get the best reception for these two cases?
  7. Your TV stops working properly, so that all you see when you turn it on is a thin, bright, horizontal line in the center of the screen. Which component (i.e., what function) do you suspect has failed?
  8. On your TV is a picture of the bright sky as seen through the dark, vertical bars of a jail cell. As the electron beam sweeps horizontally across the screen, its intensity must be modulated to draw your picture. Assuming that the brightness is related to the current sent to the electron gun, draw a plot of what you would expect the current to look like as a function of time for a single horizontal line being drawn across the screen.


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