Warming up on resonance

This assignment is due before 9 AM, Wednesday, November 15th, 2000.

Please type LAST name:

Please type your Student ID Number:

The following three questions refer to the material you were to read in preparation to the lesson. Questions one and two require you to write a three or four sentence response. Number three is a multiple choice question. Click in the appropriate circle.

You may change your mind as often as you wish. When you are satisfied with your responses, click the SUBMIT HOMEWORK button at the bottom of this page.

WarmUp questions are worth 5 points each towards your "Homework and Web Assignments" score (250 points total).




1.

Home Experiment: Make a pendulum using a string 1 to 1.5 meters long (40-60 inches), and a mass similar to a lemon (go ahead, use a lemon!). This will give you a pendulum with a resonant period in the range 2 to 2.5 seconds (T = 2{L/g}1/2). In terms of frequency, f = 1/T, so the resonant frequency is between 0.5 and 0.4 Hz.

Now, hold the end of the string and move it back and forth by 5 cm, slowly varying the frequency of your oscillation. When you find the right frequency, the lemon will swing back and forth with quite a large amplitude. This is the resonant period for your pendulum.

Try swinging the lemon a little more slowly (longer period than at resonance), how does the amplitude change? Next, try going a little more quickly than at resonance. What happens to the amplitude now?

Compare the experiment you just did to an RLC circuit. What component in your experiment is the equivalent of the ac source?



2.

A radio has RLC circuits inside that oscillate at the same frequencies as the radio waves they receive (88.1-107.9 MHz for FM, 540-1180 KHz for AM). Select values of L and C that could be used to make these circuits.





3.


In a series R-L-C circuit, which of the following statements is true at resonance?

The source power and the phase angle are both maximized.

The source power and the phase angle are both zero.

The source power is zero but the phase angle is large.

The source power is large but the phase angle is zero.

None of the above.

Below is a space for your thoughts, including general comments about today's assignment. What was hard or confusing (or cool)? What would you like to spend extra time on in class? Do you see how this subject fits in with the others we have discussed?




You may change your mind as often as you wish. When you are satisfied with your responses click the SUBMIT button.

I received no help from anyone on this assignment.



This site is made possible by funding from the National Science Foundation (DUE-9981111).
©2001 A. Gavrin and G. Novak, all rights reserved.