Electric Force and Static Charges
Goal: To observe and measure electrical force due to static charges.
Materials and Procedure
- Read up on electrostatic charges and the electroscope at
the physics classroom. Check out historical electroscopes to get a better idea of your options for building one: Kenyon University site.
- Make an electroscope:
You can use either this link to make a very simple electroscope, or this one for a science fair project electroscope, depending on the materials you have available. For either one, you may want to think about how you could change the container to make quantitative measurements of the separation of the leaves.
If you want to make a more accurate electroscope, try these instructions: 1955 Popular Electronics article.
This simple device will allow you to detect charge in various household objects.
- Calculate the force necessary to raise your electroscope "wings" to 10, 20, 30, and 40 degrees of separation against the pull of gravity. [where 0 is vertical and 10 degrees of separation is a 5 degree swing sideways for each wing.]
- Estimate the charge necessary to create the force for each calibrated distance above.
- Record the separation caused by bringing the electroscope near at least three different charged objects.
- Record the mass of the wings.
- Record the distance each wing moves to reach an angle of 10° to 40°.
- Calculate the potential energy change when the wing is in high position (U = mgh)
- Calculate the electrical force required to perform this work.
- Estimate the actual charges on the objectes you measured.
- Describe your materials, equipment, an dprocedures in sufficient detail that your fellow students could repeat your experiment.
- Report your data. 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.
- Show a sample calculation, if you have calculated values.
- 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).
- You may use a spreadsheet to calculate your information and create your table.
- Summarize your results.
- Draw conclusions about what is happening.
- Suggest at least one way to improve your experiment.
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