Physics Core/AP 1 and 2

Physics Lab

Physics Lab: Complex Circuits with Maximum Loads

Goal: To construct a complex circuit to a specific design to support maximum load..

Materials

Review the definitions and examples of resistors in parallel and series at the Physics Classroom. Use the resitors in your kit (you can buy additional resistors at Radio Shack or scavange them from broken electrical equipment if your want) and build several circuits cimilar to those in the diagrams. See if you can decode the resistor rating from the colored circles on the side of the resistor.

Use the light bulbs in your kit, or purchase additional "load" components (buzzers, other lights). Identify the resistance and voltage drop across each component, and the maximum current possible.

If you decide to purchase components, you may be able to play with a variable resistor and determine how changing the resistance affects other components on the circuit (such as the brightness of a lightbulb).

Procedure

1. Randomly select 3 resistors and 2 load items.
2. A third load item will be your ammeter, voltmeter, or multimeter.
3. Design a circuit and create a standard circuit diagram for the objects. Your goal is to maximize support for your load, that is, create a circuit with the greatest allowed current through each item (while not exceeding the item's current range). You should be able to place your meter at different locations in your circuit to measure current or potential.
4. Put your circuit together and measure current through each loop, before and after each load.

Data Handling

1. Calculate potential based on current measurments, resistor layout, and your circuit design. How do your calculations compare with your voltage source?
2. Create accurate diagrams of your circuits using conventional circuit symbols (see text for examples).
3. If you were able to use an ammeter, calculate the current on each wire in at least two circuit layouts, and compare the calculated with measured values. Explain any differences.

Report

1. Describe your materials, equipment, and procedures in sufficient detail that your fellow students could repeat your experiment.
2. Report your data. This should include your circuit diagrams, your predictions of circuit behavior, and the actual circuit behavior. Be sure to indicate the amount of error in your measurements. For example, if you can only measure a mass of 25 gms within 1 grm, your error would be 25 ± 1, or 1/25 = 4%. Present your data in an organized form, preferably in a table, in such a way it is easy to compare results as you repeate trials or vary a specific contributing factor.
3. Show a sample calculation, if you have calculated values.
4. If you did a series of experiments, varying something by increasing or decreasing a factor, try to plot your data (y-axis) as a function of the factor (x-axis).