Intro Size of electron and electron orbit in respect to perceived matter. Force: electron and proton vs. gravity Tape, wool, balloon, paper punch holes, graphite styrofoam balls

Warm up Given: –a=3, b=3 –Find  Given: –a=4, b=7 –Find  Given: –a=5, b=8 –Find  a b  c

Electrostatics Force and Charge

Charges Like charges repel Opposite charges attract

Like charges Each strip of clear tape has the same type of charge when prepared in the same manner (i.e. both positive or both negative) –These strips of tape repel each other

Opposite charges When one strip is peeled from the roll and one strip is peel from the desk, the charges are opposite. –These strips of tape attract each other.

Electrostatic related words Neutral –Equal number of positive and negative charges Insulator –Charge does not move easily through this material (e.g. plastic or styrofoam) Conductor –Charge moves easily through this material (e.g. metals)

Electric Force Force between two point sources

Electric force Two kinds of electric charges: positive and negative Charges exert forces on other charges at a distance (contact not required) The force decreases with distance Like charges repel; opposite charges attract.

Electroscope Charging by conduction: object come into contact Charging by induction: object are in proximity but never touch (requires grounding) Examples Wool Monitor Tape Balloon Van Degraff Plastic Example: electroscope

Charging by conduction A charge is created on an object. The object is brought into contact with another object. The electrons transfer to even out the distribution Example: pans

Charging by induction Charge is created on an object. The object is brought near another object (which is grounded). The charged object repels or attract electrons on the grounded object. The grounded object transfers electrons to or from the ground to reach equilibrium. If the ground is removed, the previously grounded object will have an unbalanced number of electrons and now be charged. Example: styrofoam

Force and distance Force increases with charge Force decreases with distance

Proportional to the inverse square q A =10C, q B =10C –r=1mm –r=1.414mm –r=2mm –r=3mm –r=4mm –r=5mm –r=6mm Find the pattern Pg 552 #11

Homework Pg 557: –Explain Key Concepts in your own words. –Relate to your things you experience in real life. Ch 20 Study Guide Pg 558 #20-40 Pg 559 #42-49, 51,59,60

Concepts section 1

Concepts section 2

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