Circuits Laboratory

This series of experiments provides a good visual connection to how current flows in circuits and how current, voltage, and power (lamp brightness) are related.

Equipment:
A six volt battery or protected power supply, three six volt lamps in holders, six wires with alligator clip ends, two double-pole single-throw (DPST) switches, and a diode.

Procedure:
The light bulbs will provide resistance in the circuits. The resistance of the wires is very small compared to that of the lamp bulbs and can be ignored. You will perform the following tasks. If your are uncertain about the results at any stage, be sure to discuss your uncertainties with the instructor before moving to the next task.

Important: Be sure that the battery is not shorted at any time. That is, there should never be a direct wire connection between the two terminals of the battery. Construct all circuits by placing the battery into the circuit at the last step. If you are uncertain, ask the instructor for help before placing the battery into the circuit.

1. Use the battery, a bulb, and two wires to complete a circuit and make the bulb glow. Repeat with only one wire and maybe something else in the room.

2. Connect two bulbs in all possible combinations that produce glowing bulbs. Draw circuit diagrams for each. Discuss the brightness of the bulbs in all cases and explain in terms of current flow.

3. Sketch diagrams for all possible combinations of 3 bulbs, predict the brightness for each case, and then test your predictions.

4. Place a diode in series with one bulb and observe the results. Switch the orientation of the diode and repeat. What function does the diode perform?

5. Place a DPST switch in series with a bulb such that the switch can be turned on and off.

6. Place two bulbs and the DPST switch into a circuit such that each bulb lights in a different switch position.

7. Construct Circuit #7 shown below and predict the results for the different switch positions. Try it! Design your own circuit that turns each bulb off alternately with just one switch.

8. Construct and predict the results for Circuit #8 shown below. For what purpose do you think such a circuit is used.

Report

Describe the results qualitatively for each task above. Include any circuit diagrams you were requested to draw and any others that will help with your description.

In several instances, you were asked to make predictions before testing a circuit. In your report, state your original predictions and the reasoning that led to those predictions. If your predictions were incorrect, explain those ideas or concepts that you think brought you to those erroneous predictions. (Note: Incorrect original predictions will NOT factor into the grade of your report! Be honest about what confused you and what you learned. This will help us with revisions of this lab.)