live interactive learning @ your desktop tuesday, january 30, 2007 7:00 p.m. to 8:00 p.m. eastern...
TRANSCRIPT
LIVE INTERACTIVE LEARNING @ YOUR DESKTOP
Tuesday, January 30, 2007
7:00 p.m. to 8:00 p.m. Eastern time
NSDL/NSTA Web Seminar:
Charging into Electrostatics
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• Access to multiple collections in Physics and Astronomy
• ComPADRE: the NSDL Physics & Astronomy Pathway
• PhysicsFront.org Special ComPADRE collection for secondary level teachers
•
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Charging into Electrostatics
An NSDL/AAPT/ComPADREPresentation by
Jan Mader and Dr. Cathy Ezrailson
Test Yourself
In which direction will charges move in the diagram shown:
A)To the left
B)To the right
C)The electrons will not move
+ -
-
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“Static” Electricity
When you comb your hair and…
… bring your comb over a pile of paper bits
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“Static” Electricity What will happen? Stamp your answer
A. B.
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“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.
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Match the diagram below with its correct description.
1. 2. 3.
A. B. C.
Deficiency of Electrons Net Charge
Positive
Balanced atom Net Charge
Zero
Excess of Electrons Net Charge
Negative
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“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.
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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.
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Methods of Charging
Direct contact Induction
Results in a transfer of charges
Usually results in a temporary rearrangement of charges
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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.
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Self Check?
True False
True FalseCharges flow from less negative to more negative areas.
Like charges repel.
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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.
Third Step:
Pick up the tape “handles” and pull the tapes apart.
Making a Magic Tape Electroscope
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Making a Magic Tape Electroscope
The tapes separate as shown. What do you think causes this to occur?
1.
2.
3.
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
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Charge QuizWhat are the charges on the objects shown?
How can you tell?
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Use the + or – stamp to indicate the charge on the picture
Rub the Styrofoam plate with cloth or a paper towel.
PT III: Charging an Electrophorus
Set the pie tin down on the picnic plate.
Hold it by the plastic cup.
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.
Using an Electrophorus to Store Charge
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.
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Charging by Induction QuizDoes the diagram below illustrate permanent
or temporary charging by induction?
Permanent Temporary
Step I Step I I Step I I I Step IV
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
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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
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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
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THANK YOU!
Dr. Cathy [email protected]
Robert [email protected]
http://compadre.org
ThePhysicsFront.org
National Science Teachers AssociationGerry Wheeler, Executive Director
Frank Owens, Associate Executive Director Conferences and Programs
Al Byers, Assistant Executive Director e-Learning
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NSTA Web SeminarsFlavio Mendez, Program Manager
Jeff Layman, Technical CoordinatorSusan Hurstcalderone, Volunteer Chat Moderator