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:
- Draw an AM signal conveying a triangle wave sound waveform:
- Draw an FM signal conveying a square wave sound waveform:
- 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.)
- 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
quartwhich is 32 ounces. Assume that all of the microwave's power
is absorbed by the water.
- 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?
- 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?
- 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?
- 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.