NSC 101 Laboratory for 3/3/98

Electricity

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-pull double-throw (DPDT) 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 have the following tasks. We will have a brief class discussion after each task.

  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 discuss results.
  5. Place a DPDT switch in series with a bulb such that the switch can be turned on and off. Carefully check your circuit before you close the switch.
  6. Place two bulbs and DPDT switch into a circuit such that each bulb lights in a different switch position. Discuss the different possiblities for doing this.
  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.