The Case of the Crooked Carnival (10 page)

7.
Now connect one end of the wire to the positive battery terminal (if it’s not labeled, either terminal is fine as long as you connect one wire per terminal, creating a complete circuit) and the other end to one of the paper fasteners.

8.
Cut a second piece of insulated wire, about 2½ feet long. Again, strip the ends and attach the alligator clips. Wrap the wire tightly about 20 times around the nail, leaving at least 8 inches of loose wire at each end.

9.
Connect one end of the wire to the negative battery terminal (again, if the battery isn’t labeled, just use the opposite terminal), and the other end to the remaining paper fastener.

10.
Ta-da! Congratulations! You have now completed your own Handy-Dandy Paper Clip Picker-Upper! Gigantic applause PLEASE!

11.
Whoops … You still need to turn on the switch in order to complete the electrical circuit. (Remember Frisco? He had his hand in his pocket? Switch on. Switch off. On. Off.) To turn the switch on, press down on the large arm of the paper clip so that it touches the second brass fastener. Your circuit is now complete, and your electromagnet is active. When you want to deactivate it, simply release the switch.

12.
See how many paper clips you can pick up using your electromagnet.

Warning #1:
Keep magnet away from DVDs, CDs, audiotapes, electronic devices, and computers, as it may damage them.

Warning #2:
Magnets can release some of their energy in the form of heat. If your magnet becomes too warm, disconnect it until it cools off. Always disconnect it when not in use.

More Cool Stuff:

1.
The strength of your magnet depends upon how many coils of wire you wrap around the nail. Using varying lengths of wire, coil it 10 times, 25 times, 50 times…. Write a hypothesis as to what you think will happen, and then test your hypothesis. Were you correct?

2.
The size of the nail also affects magnet strength. Write a hypothesis, and then test it using different sized nails.

3.
How can you bypass the switch to your electromagnet like Drake did under Shady Jim’s booth? Test your hypothesis.

4.
Instead of paper clips, try iron filings (ask at an auto-mechanic shop—they usually have iron filings for free, or you can buy a jar full from
www.dowlingmagnets.com
).

I
t’s T minus 30 minutes. The weather is simply ghastly, and the parade is about to begin. Soon it will march down Main Street, past Barko’s Supermart and Iggy’s Ice Cream Parlor … marching toward Mossy Lake Bridge … and
disaster!
It’s up to you, Horace Peabody or Polly Plum (choose one), to save the day! But first you must develop a hypothesis:

“I believe the Mossy Lake Bridge is going bananas because ________________.” (Hint: If you can’t think of a hypothesis, reread parade/ bridge/bananas scene.)

Then you must build a simulation to test your hypothesis. Here’s how:

MATERIALS

•  2 chairs

•  string

•  scissors

•  2 cedar hanger rings (circular cedar discs with hole cut in middle, available at department stores or online; if you can’t find any, use a substitute such as old CDs)

•  hair dryer

PROCEDURE

1.
Place the chairs back to back.

2.
Cut a piece of string approximately 10 feet long. Tie one end of the string to the back of one of the chairs.

3.
Thread the string through the center of the two cedar hanger rings, and tie the other end of the string to the back of the other chair. Adjust the distance between the two chairs so that the string forms a “bridge,” with the cedar rings hanging in the center of the bridge. There should be plenty of slack.

4.
Standing beside the bridge, pull the cedar rings toward you and let go. The bridge should swing back and forth in a large arc, gradually becoming weaker before eventually stopping.

5.
Try #4 again, except this time clap your hands every time the bridge is closest to you. Notice how the rhythm of your clapping stays the same, regardless of how big or small the arc of the swinging bridge is.
This rhythm is the natural frequency of the bridge.

6.
Again pull the cedar rings toward you and let go. Now, using the hair dryer, blast the cedar rings with air every time they move away from you (as if you were pushing someone on a swing, pushing the person away from you as the swing moves away). What happens? (Remember, this is called
resonance
. You are adding a force at the same frequency, which creates more vibration.)

7.
Try the same thing again, except this time blast the cedar rings with air every time they move
toward
you. What happens?

8.
Pedal like mad to the parade and save the day. Congratulations! You are a hero!

Check This Out!

From the moment it was built in 1940, the Tacoma Narrows Bridge had a severe case of the hiccups. On a windy day only four months after it was completed, “Galloping Gertie” collapsed into Puget Sound. Watch the video at:
http://www.youtube.com/watch?v=3mclp9QmCGs
. How would you like to try to drive across
that??!! Yikes!!
(Note: If you have difficulty finding the video, simply go to
www.youtube.com
and search for “Tacoma Narrows Bridge.”)