# Describe various aspects of electrostatic and magnetism Describe how to present this information with a hands on demonstrations. You will be able to:

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Describe various aspects of electrostatic and magnetism Describe how to present this information with a hands on demonstrations. You will be able to: http://vip.vast.org/VAST2009

ELECTROSTATICSELECTROSTATICS Can cell phones start a fire at the gas pump? Where does lightning come from and what do we know about it? Should I lie down in a field if lightning is near? Did Ben Franklin really fly a kite in a storm is that a tall-tale like Newton being hit on the head by an apple. What does this have to do with sharks?

ELECTROSTATICSELECTROSTATICS Without saying anything, What do you think we will study in this unit?

Electrostatics The study of stationary charges.

Activity After doing this activity, write down your observations and inferences on piece of paper. Everybody does one. 1.Rub the tube or stick with fur. 2.Glide the spoon filled with coffee creamer across the length.

InsulatorsConductors Material that does allow the migration of charge. NOT Material that does NOT allow the migration of charge. Let’s list some insulators and conductors on the board. The choice of the word “migration” is very deliberate. This means the motion of charges from point “A” to point “B.” It does NOT mean charges can’t move.

InsulatorsConductors plastic glass cloth paper dry air ceramics rubber cork wood (poorly) metals (not lead) “dirty” water plasma wet air graphite wood (poorly)

Insulators Power lines Power lines

Insulators

Pass around the insulator. Train image from: http://www.trainnet.org/Libraries/Lib019/18_478.JPGhttp://www.trainnet.org/Libraries/Lib019/18_478.JPG

Charging objects Charge Model: Objects get a net charge by the movement of either positive or negative charges. Example: To become positive; negative charges can be lost or positive charges can be gained. Charge Model Rule: Like charges repel. Opposites attract.

Nature of materials Some materials like to collect electrons while others like to give them away. Triboelectric effect To charge by rubbing.

The Triboelectric Effect

Nature of materials Some materials like to collect electrons while others like to give them away. This is called “electron affinity.” Electron affinity is measured with the “relative electronegativity scale.” Triboelectric effect To charge by rubbing.

Relative Electronegativity Scale + + + + + + + + + + + - - - - - - - - - - - Glass (hates electrons.) Human hair Nylon Silk Fur Aluminum Paper Cotton Copper Rubber PVC Teflon (loves electrons.) The farther apart two materials are on the scale, the larger the charge difference they create.

Relative Electronegativity Scale + + + + + + + + + + + - - - - - - - - - - - Glass (hates electrons.) Human hair Nylon Silk Fur Aluminum Paper Cotton Copper Rubber PVC Teflon (loves electrons.) If human hair is rubbed on a rubber balloon. Which object will become negatively charged? Rubber because it likes electrons more on the scale.

Relative Electronegativity Scale + + + + + + + + + + + - - - - - - - - - - - Glass (hates electrons.) Human hair Nylon Silk Fur Aluminum Paper Cotton Copper Rubber PVC Teflon (loves electrons.) If nylon is rubbed on glass. Which object will become negatively charged? Nylon because it likes electrons more on the scale.

Relative Electronegativity Scale + + + + + + + + + + + - - - - - - - - - - - Glass (hates electrons.) Human hair Nylon Silk Fur Aluminum Paper Cotton Copper Rubber PVC Teflon (loves electrons.) Which generates the greater charge Nylon rubbing on cotton or Fur rubbed on PVC? Fur on PVC because the two items are farther apart on the scale.

Relative Electronegativity Scale + + + + + + + + + + + - - - - - - - - - - - Glass (hates electrons.) Human hair Nylon Silk Fur Aluminum Paper Cotton Copper Rubber PVC Teflon (loves electrons.) Make up a question and answer it. Do not show your question to anybody else. -wait... Form a group of 3. Have everyone answer your question. Write the group’s questions on a white baord. Discuss any answers if you disagree. I will pick some to discuss.

Charge Sharing

This video is from the “pirates” cd by “The Bare Naked Ladies”

demos!

Observation vs Inference What is a demo supposed to show? What do I write down?

- - ? Balloon rubbed with fur Another balloon rubbed with fur Bring the balloons close String attached to the ceiling

- Balloons all rubbed with fur Bring a match under them. Keep the match about 1 foot away so the balloons do not pop. Strings attached to the ceiling - -

Aluminum can - Balloon rubbed with fur You could also use the fur rubbed on the pvc pipe. Bring the balloon close the can without touching it.

- Balloon rubbed with fur. Bring the balloon close the can without touching it. Meter stick or 2” x 4” x 8’ board String attached to the ceiling. Explain in terms of the charge model.

- Ceiling Balloon rubbed with fur.

This 90 second clip is from “Mythbusters” on the Discovery Channel, episode 14. Air date: June 14, 2008.

Review: Triboelectric Effect Charge sharing Charging by induction

Lightning

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