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LIVE INTERACTIVE LEARNING @ YOUR DESKTOP NSDL/NSTA Web Seminar: Charging into Electrostatics Tuesday, January 30, 2007 7:00 p.m. to 8:00 p.m. Eastern time

http://nsdl.org http://nsdl.org • Access to multiple collections in Physics and Astronomy • ComPADRE: the NSDL Physics & • Astronomy Pathway • PhysicsFront.org Special ComPADRE collection for secondary level teachers

Charging into Electrostatics An NSDL/AAPT/ComPADRE Presentation by Jan Mader and Dr. Cathy Ezrailson

http://nsdl.org Test Yourself In which direction will charges move in the diagram shown: • To the left • To the right • The electrons will not move + - -

http://nsdl.org “Static” Electricity When you comb your hair and… … bring your comb over a pile of paper bits

http://nsdl.org “Static” Electricity What will happen? Stamp your answer A. B.

http://nsdl.org “Static” Electricity • The force felt by the paper bits is due to a difference in charge on the comb compared to the paper. • This “force of attraction” was first observed by the Greeks who found that piece of amber (“elektron”) attracted other objects when rubbed.

C. A. B. http://nsdl.org Match the diagram below with its correct description. 1. 2. 3. Excess of Electrons Net Charge Negative Deficiency of Electrons Net Charge Positive Balanced atom Net Charge Zero

http://nsdl.org “Static” Electricity • Usually charges balance each other out, and nothing happens. But when two objects with like charges (all positive or all negative) come together, the charges repel and the objects move away from each other. • Objects with opposite charges attract each other because the different charges want to balance each other. • Objects can get a negative charge by picking up electrons from other objects.

http://nsdl.org Common Misconceptions about “Static” Electricity Actually, the thing we call static electricity is an imbalance in the amounts of positive and negative charges found on the surface of an object.

http://nsdl.org Methods of Charging Induction Direct contact Usually results in a temporary rearrangement of charges Results in a transfer of charges

http://nsdl.org Common Misconceptions about “Static” Electricity Lightning is like static electricity, except on a much bigger scale. Both lightning and static electricity happen because of the attraction between the opposite charges.

http://nsdl.org Self Check? Charges flow from less negative to more negative areas. Like charges repel.

Pt II: Making a Magic Tape Electroscope First Step: Bend back one end on each of two tapes to make a handle. Second Step: Lay each piece of magic tape on top of each other on a smooth surface.

http://nsdl.org Making a Magic Tape Electroscope Third Step: Pick up the tape “handles” and pull the tapes apart.

Making a Magic Tape Electroscope The tapes separate as shown. What do you think causes this to occur?

http://nsdl.org Making a Magic Tape Electroscope • Charges on the surface of the tapes shown are alike • Do we know whether these charges are positive or negative? • How could we tell? Write your answers on the chat

http://nsdl.org Charge Quiz What are the charges on the objects shown? Use the + or – stamp to indicate the charge on the picture How can you tell?

PT III: Charging an Electrophorus Set the pie tin down on the picnic plate. Hold it by the plastic cup. Rub the Styrofoam plate with cloth or a paper towel.

Using an Electrophorus to Store Charge Touch the foil-wrapped cardboard and the pie tin at the same time, then let go. Hold the plastic cup and lift the pie tin. Touch it to the nail on the Leyden Jar. Repeat.

http://nsdl.org The Leyden Jar • The Leyden jar is a device for storing electric charge invented in 1745 by Pieter van Musschenbroek (1700–1748). • Mr. Muschenbroek’s bottle is referred to as the “phial” by Benjamin Franklin. Today, we would call it a capacitor.

Charging by Induction Quiz Does the diagram below illustrate permanent or temporary charging by induction? Step I Step I I Step I I I Step IV

http://nsdl.org ThePhysicsFront Resources • Let’s go to The Physics Front and look at what resources are available to you and your fellow teachers • http://thephysicsfront.org

http://nsdl.org Credits • Benjamin Franklin and Electrostatics by Robert Morse http://www.tufts.edu/as/wright_center/fellows/bob_morse_04/ • Museum of Science, Boston, http://www.mos.org/sln/toe/staticintro.html • The Weather Eye http://weathereye.kgan.com/cadet/lightning/electricity.html • Practical Physics, published in 1914 by Macmillan and Company

http://nsdl.org Go to http://nsdl.org and click on the K-12 audience page • Download this seminar’s companion guide with resources from the seminar and more • Expert Voices blog with our presenters http://expertvoices.nsdl.org

http://nsdl.org http://compadre.org ThePhysicsFront.org Dr. Cathy Ezrailson cezrailson@tamu.edu THANK YOU! Jan Mader jan_mader@gfps.k12.mt.us Robert Payo rpayo@nsdl.ucar.org

National Science Teachers Association Gerry Wheeler, Executive Director Frank Owens, Associate Executive Director Conferences and Programs Al Byers, Assistant Executive Director e-Learning NSTA Web Seminars Flavio Mendez, Program Manager Jeff Layman, Technical Coordinator Susan Hurstcalderone, Volunteer Chat Moderator LIVE INTERACTIVE LEARNING @ YOUR DESKTOP

LIVE INTERACTIVE LEARNING @ YOUR DESKTOP