Academic journal article The Science Teacher

Try This Tops Idea!

Academic journal article The Science Teacher

Try This Tops Idea!

Article excerpt

[ILLUSTRATION OMITTED]

1. Stick about 15 cm of clear tape to the dull side of aluminum foil. Trim away all untaped foil.

[ILLUSTRATION OMITTED]

2. Hold your bi-material strip high above a flame. Which way does it bend?

3. Aluminum and tape expand when heating and contract when cooling.

a. Are the changes equal for both materials? Explain.

b. How does a bimetal strip work in a thermostat?

[ILLUSTRATION OMITTED]

* PROJECT: Light a flashlight bulb with a candle. Use your bi-material strip, batteries, and other simple things.

OBJECTIVE

To observe how a bi-material strip bends as its dissimilar sides expand and contract by different amounts. To apply this idea to thermostats.

LAB NOTES / ANSWERS

Photocopy the activity for each student or team.

Step 2. The strip bends toward its aluminum side as it heats up, and away from its aluminum side as it cools down.

Step 3a. No. On heating, the tape expands (lengthens) faster, bending toward the relatively shorter aluminum. On cooling, the tape con- tracts (shortens) faster, bending away from the relatively longer aluminum side. …

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