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Electrostatic Charge TransferHow do objects get charged?Electrons can moveConductorselectrons are free and can move throughout the materialin good conductors, can move from atom to atom, and object to objectInsulatorsdo not allow free movement of electrons throughout the material, or from the object to other thingsCharges within objects are separatedNeutral atoms/objects equal protons and electronsCharged atoms/objects more or less electrons than protons (depending on charge)Most of this should be review, but needs to be reviewed in order to talk about charging.2Law of Conservation of Electric Chargenet charges must equal zeroWithin and object:If part of an object becomes charged, the other part of an object must become equally and oppositely charged. Example: water moleculesNegative PoleNet overall charge: 0

Positive PoleBetween 2 Objects:If an object becomes charged from interacting with another, the other object must become equally, but oppositely, charged

4 Ways to Charge Objects

#1: PolarizationSurface charge (object remains neutral, overall)Charges within object shiftin response to being near a charged objectOnly while near the charged object.

LightningLightningFriction causes build-up of electrostatic charges in cloudsBottom of cloud is usually negativeNegative buildup repels electrons in the ground, so surface becomes positive.

With enough buildupElectrons are attracted to the earth and come down in a streamer of negative charges.Positively charged air particles near the surface of the earth are repelled by the ground and form a streamer upwards.

When the streamers connect, a conductive path for an electron surge is formed lightning occurs!Air particles are so excited they emit lightAir is heated so intensely in creates sound waves (thunder)many billions of electrons are transferred at the same time (up to 100 million volts)Lightning bolts ionize the atoms in the air producing great amounts of heat (a little hotter than the sun) causing compressional waves (sound) called thunder

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Polarization DemoWatch the demo and answer the questions on your worksheet.Experiment #1Charging by polarization.Rub the round end of the balloon with the fur for a few seconds. Hold the balloon against the wall and release it.Observe what happens.

4 Ways to Charge Objects#2: FrictionElectrons transfer between objects by rubbing 2 neutral objects together (objects must have different affinities for electrons)

You DONT have to talk about the triboelectric scale, we arent testing it or doing a lab over it.12Charging by Friction

Experiment #2Charging by friction.Rub one of the balloons on your hair for a few seconds.Immediately hold it close to the other balloon.Observe what happens.

#3: Conduction: - Requires one charged object, & one neutral object.pith ball simulation4 Ways to Charge ObjectsGo through the simulation FIRST, and have students answer the questions.15

Step 1: Objects brought together to touchStep 2: electrons transferred from charged to neutral (but polarized) object

Step 3: both objects now identically charged and repel one another.The Electroscopemade of two thin metal leaves attached to a metal rod with a knob at the top.

- when the device is not charged, the leaves hang straight down.

- when an electric charge is present, the leaves repel each other, spreading apart.electroscope simulationsElectroscope

4 Ways to Charge Objects

#4: Induction: Two neutral objects are in contact. A third, charged object, is brought near the neutral objects to make them polarized.The now polarized objects are separated making two oppositely charged objects. Starts similar to polarization, but electrons pushed from one object into the other.20Teacher DemoDraw a picture of what is happening to the charges in the aluminum cans.

Groundingphet - travolta

K ExtensionsConductors: metals, aqueous solutions of salts (i.e., ionic compounds dissolved in water), graphite, water, and the human body. Insulators: plastics, styrofoam, paper, rubber, glass, and dry air.

How a Van de Graaff Generator Works:

Van de Graaff videoSharing Charge via ConductionA metal sphere (A) with a charge of +4 units is brought in contact with a metal sphere (B) with -2 units of charge, and the spheres are then separated. What is the charge on each sphere after separation?AB-+-+-++-+-+-++AB+4-2++++-+---+-+-+AB-+-+-++-+-+-++