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Fun Electrical Circuits
This page: http://pierce.wesleyancollege.edu/faculty/MSP/orientex/kitcircuits.html
For these exercises we will be using the materials in your electrical circuit kit. Additional kits may be obtained from The Science Fair, Inc.
A nice series of age-appropriate experiments with wiring diagrams are may be found at at GalaxyNet: http://www.galaxy.net/~k12/electric/#exper .
Circuit #1 - Lamp
1) Find the two lamp housings. Use a mounting square to secure each one to opposite ends of the top of the small wooden block.
2) If necessary detach the two battery holders from each other. Insert a D-cell battery into each holder, paying attention to the correct orientation of the battery.
3) Use the alligator clip jumper cables to connect each pole of the battery to one of the two screws on either side of one of the lamp housings. Screw in a lamp bulb. This should complete the circuit and light the lamp. Trace the completed circuit from the battery, through the lamp and back to the battery.
4) Use your multimeter to measure the voltage between the two poles of the battery, between the positive pole of the battery and the lamp, between the lamp and the negative pole of the battery, and between the two lamp terminals (across the lamp). Where in this circuit do the "voltage drops" of 1.5 volts occur?
5) What do you think will happen if you add the other battery into this circuit in series? Clip the two battery holders together end to end and adjust your jumper cables so that both batteries are supplying the lamp. Is ther any change in the brightness of the lamp? Can you explain this change? Is this change due to a change in voltage through the lamp, current through the lamp, or both? Use your multimeter to determine this.
Circuit #2 - Switched Lamp
1) Use a third jumper cable to wire the kit switch into your circuit, between the positive pole of the batteries and the lamp. If you turn over the switch you can see that one switch terminal is wired to the base of the switch and the other is wired to the contact point. Test the switch a few time to make sure that it works.
2) Does pressing the switch lever open or close the circuit? Try wiring the switch between the positive battery pole and the lamp, between the lamp and the negative battery pole, and between the two batteries. Does it matter where in the circuit the switch is located?
3) Replace the store-bought switch with your home-made clothes pin switch. How does it work?
Circuit #3 - Series Lamps
1) Unclip all of your jumper wires. Screw a lamp bulb into the other lamp holder.
2) Wire a circuit that runs from the positive battery terminal to one switch terminal, from the other switch terminal to one terminal of lamp A, from the other terminal of lamp A to one terminal of lamp B, and from the other terminal of lamp B to the negative battery terminal.
3) Close the switch. Is either lamp as bright as the single lamp was? Why or why not, do you suppose?
3) Trace your circuit. Note that the circuit passes through each lamp in series. In this configuration does each lamp experience the total 3V voltage? Use your multimeter to test this. Does each lamp experience the same current? Again, use your multimeter to test this.
4) What do you think will happen if you unscrew one of the lamp bulbs? Try it and find out. Can you explain why this happens?
5) Would this be a good way to wire multiple appliances in your house? Why or why not?
Circuit #4 - Parallel Lamps
1) Unclip all of your jumper wires. Screw both lamp bulbs back in.
2) Wire a circuit that runs from the positive battery terminal to one switch terminal, from the other switch terminal to one terminal of lamp A, and from the other terminal of lamp A back to the negative battery terminal. Push the switch and see how bright the lamp is.
3) Now use two more jumper cables to connect each terminal of lamp B to one of the terminals of lamp A. Close the switch. Is either lamp as bright as the single lamp was?
4) Trace the circuit you have created. Notice that the two lamps are now wired in parallel. In this configuration does each lamp experience the total 3V voltage? Use your multimeter to test this. Does each lamp experience the same current? Again, use your multimeter to test this.
5) Are the two lamps in this configuration brighter than they were in the series configuration? You may want to collaborate with a neighbor and set up side-by-side parallel and series circuits to compare.
6) What do you think will happen if you unscrew one of the lamp bulbs? Try it and find out. Can you explain why this happens?
7) Would this be a better way to wire multiple appliances in your house? Why or why not?
Additional Circuits
If you have time, try to set up and test the signaling circuit and/or the simple computer circuit found at the GalaxyNet site.
The coordinators will also demonstrate a old-fashioned doorbell circuit, which uses an interrupting magnet switch. Can you figure out how this circuit operates?
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