Vernier Software and Technology
Vernier Software & Technology
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What types of activities can I perform with the Charge Sensor?

See the article "Electrostatics with Computer-Interfaced Charge Sensors" by Robert Morse in The Physics Teacher, vol 44, November 2006, pages 498-502. This short article is an excellent introduction to simple experiments for charge sensors.

For more detail, see the book entitled "Teaching About Electrostatics" also by Robert A. Morse. It is an excellent source of ideas. The book also contains a CD called "Benjamin Franklin as My Lab Partner". A number of the ideas described below come from Bob Morse. This book is available at the AAPT store at:
http://www.aapt.org/Store/description.cfm?ID=WSP-01&Category=All&Type=All&Level=All&Keywords=

You can easily demonstrate charging mechanisms. For example you can simply comb your hair and touch the red lead of the sensor with the comb. You will observe an increase in sensor reading. If you repeat the process, you will note the reading increase with each touch. Other good examples include the charging of a Styrofoam cup by simply handling it, or the charging of an electrophorus, which can be made out of an aluminum pie plate.

As you work with the sensor, you may notice that you personally carry charge. It may be necessary for you to ground yourself before carrying out experiment. You may want to demonstrate this to your students.

You can demonstrate charging by induction. Place two soda cans on a glass plate. Ground one of the cans and charge the other can. Bring the charged can near the grounded can and remove the ground. Now use the sensor to explore the charge on the previously grounded can.

You can demonstrate charging by contact. An excellent demonstration can be performed with Scotch™ Magic™ tape. Obtain two 5-cm pieces of magic tape. Fold the top of one into a point. Fold the top of the other one over straight. Put the one with pointed top on top of the other tape with the sticky side of the pointed tape on top of the smooth side of the straight folded tape. With the two pieces of tape stuck together, ground the tape. Show that they have no charge by moving them near the red lead of the charge sensor, which is held out in space by an insulator. Now pull the two pieces of tape apart. Move each piece near the red lead of the charge sensor and show they are charged in opposite ways. Now, put the two pieces of tape back together. Move the combination near the red lead and show that the combination is not charged.

Make an Al foil ball and suspend it between two cans with a bifilar support. Clip the red Charge Sensor lead to one can, which has been grounded. Charge the other can and let the foil ball bounce back and forth between the two cans as you watch the charge increase on the can with the red lead.

Demonstrations can be performed with an inexpensive Faraday Pail, which is an excellent way to do some qualitative studies. To make the pail, cut the top off an Al foil can and put plastic electrical tape on the sharp part of the can. Charge up bits of foam by tearing up a Styrofoam foam cup. Attach the red lead of the Charge Sensor to the pail. Drop pieces of the foam into the pail and watch the charge build up. Drop pieces of foam of various sizes into the pail. Notice that they have different size charges. Dump the foam out and show that no charge has been transferred to the pail.

The Scotch Tape described above can be used with Faraday Pail. Make multiple sets of tapes and then drop the pointed ones in one at a time to show that each one has the same amount of charge. Then drop the blunt tapes in one at a time to show a decrease in the charge with each tape. You could even try tapes of differing length to show different amounts of charge.

Here is another demonstration similar to the one mentioned above. Charge up a piece of foam and put a penny on it. Touch the penny to induce a charge on it, and place the penny in the pail. Repeat the process with other pennies and watch the charge build up. Finally dump out the pennies and observe that charge has been transferred to the pail.

Another activity for use with the Faraday Pail involves a "proof plane". Build a proof plane out of an insulator with a coin at the end. Charge the proof plane and touch it to the inside of the pail which has the red lead attached. Observe the charge build up.

You can demonstrate the discharging of an object. Charge the red lead of the Charge Sensor. Now connect it to dry thread which is attached to ground. Collect data as a function of time to monitor the discharging of the sensor. Repeat the experiment with thread moistened in distilled water and thread moistened in salt water. Compare the discharge rates.

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