"Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality.” -- Nikola Tesla
Circuits Project 2009
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recent update
May 13, 2008 9:09 AM
We have done much with the theory of electric circuits, and now we are going to put some of these ideas in practice. The concepts of Voltage, Current, Resistance, Power, and such are hard! If you keep working with them, especially with your hands, you will begin to understand them.
We have a number of projects to keep you in fun circuits all through 4th quarter. Most of these projects you will need to work on at times other than in-class. You can work at your own pace, and the more projects you do, the more your projects will influence your understanding (and grade). Type up your responses to these projects and turn them in at the final exam.
You can work in groups of no more than two.
Some of the projects are required, the rest are optional. The required projects are in red. Some of the project require a signature from an instructor to verify you have built the circuit -- see notes below. It is an excellent idea to take pictures of your work with a cellphone or other camera.
Project 1: Resistance and Temperature
- Make a plot of voltage (y-axis) vs. current (x-axis) for a small lamp. The data points should fall along a line for low current & voltage (with slope V/I = R = resistance of the bulb). Measure this resistance. At sufficiently high current & voltage, the slope of the line might change. If you observe this, note whether the slope (resistance) increases or decreases. Explain your finding by considering the microscopic behavior of atoms within the lamp filament (check out
PhET: Battery-Resistor Circuit)
Project 2: Current Measurement
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Find a voltage supply (DC power supply, battery, or other source), some alligator clips, a resistor, and an ammeter. Put the ammeter in series with the resistor. Before hooking up the circuit, predict how much current will flow. If this current is greater than the highest value on the ammeter, get a bigger resistor! We don’t want to bust it. Now hook up the circuit so that current flows. Compare the measured current to your predicted current. Were you right? If not, why not?
Project 3: Parallel and Series Light Bulbs
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Try to find two light bulbs that are equal in brightness when the same voltage is put across each. Attach these light bulbs in series to a low voltage (< 10 V) power supply. Before turning on the power supply, predict whether one will be brighter or dimmer. Check your answer by turning on the voltage.
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Turn off the voltage, then hook up the light bulbs in parallel. Before turning on the power supply, predict whether one will be brighter or dimmer. ALSO, predict whether the bulbs will be brighter or dimmer than when they were hooked up in series.
Project 4: Your Calculator
- Determine whether the batteries in your calculator are placed in series or in parallel. Be sure to explain how you made your determination. Why do you think the designers chose to use the combinations of batteries they did?
Project 5: Flashlight
- Bring in a flashlight from home and determine how much current is passing through the filament when the bulb is powered. Explain your findings.
Project 6: Circuit Building [signature required] 
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Build the following circuit. Before turning on the power supply, predict what values the ammeter and voltmeter should read. Hint: when building a circuit, sometimes it helps to tape down your wires in the shape of the circuit on a piece of paper, so you can remember who everyone is.
- When finished, and with the ammeter and voltmeter reading the correct values, have an instructor sign your circuit diagram to verify your work. This signature will be included with everything you turn in.
Project 7: Upstairs/Downstairs Switch [signature required]
- Design (on your own!) a circuit that will allow you to control the on-off state of a light bulb from two separate locations. Draw a circuit diagram and then build the circuit. The circuit must not draw current when the light bulb is in the off state (since this would be dangerous!)
Project 8: Electric Car [signature required]
- Design and build an electric car that runs off of one or more D-cell batteries. You cannot spend any money on this project, but found materials are fine. Additional credit will be awarded to a student who wins a fair and organized racing competition. (It is up to you to organize and validate the competition.) You must build the motor yourself based in electromagnetic theory. When finished, have an instructor sign your circuit diagram to verify your work. This signature will be included with everything you turn in.
Project 9: Electric Motor [completed already for 2009]
- Print out these electric motor instructions and collect the materials from your instructor. Build the motor according to the specifications.
Project 10: Speaker [completed already for 2009]
- Build a speaker from a piece of paper, magnet wire, a magnet, and tape. Verify that the speaker works by attaching it to an amplifier and playing music from the radio. Talk to your instructor about how to build the speaker - usually we do this one in class.
Project 11: Wind Power Generator [signature required]
- Design and build an electric generator that is powered by the wind. You cannot spend any money on this project, but found materials are fine. Demonstrate to a physics instructor that it indeed generates at least 50 μA of alternating current when measured on a microammeter. The wind can be provided by a fan if needed.
Project 12: Solar Cell [signature required]
- Purchase a small solar cell online or at Radio Shack. Use the cell to power a circuit of your design.
Project 13: Transistors
- Write a short, one-page description of what a transistor is and how it is used. You must do original research, no plagiarism. Attach to your report an actual transistor (you can buy very cheap transistors at Radio Shack) and explain which “lead” wire is which. You can earn additional credit by making a working amplifier circuit with a transistor.
Project 14: Schematics
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Download a circuit schematic for a complicated electronic device (a guitar pedal, a VCR, a computer mouse, a digital clock, an automobile, etc.). Make a “parts list” for the circuit: that is, find out what each component is, and make a list of how many of each you will need to buy. You can find some ideas and diagrams at http://www.discovercircuits.com/front/list.htm (not all of these are free, but there are some free examples.) You might not understand every component in the circuit right now, but some day you will.
Project 15: Complicated Resistor Circuit [signature required]
- Make a really complicated circuit involving lots of parallel and series resistances (at least ten resistors in total). Copy down your circuit and predict what the current flowing through it will be given a certain input voltage. Verify your prediction by building the circuit and measuring the current.
Project 16: Telegraph [signature required]
- Read about the electric telegraph at Wikipedia.
- Build a simple telegraph according to the laboratory instructions provided here; use the telegraph to communicate a message (provided by the instructor) via Morse code from one room to another. Your instructor will provide a length of magnet wire and a telegraph key (for tapping).