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# Intro PowerPoint PPT Presentation

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. b. Given: a=3, b=3 Find  Given: a=4, b=7 Find  Given: a=5, b=8 Find . a. c. .

Intro

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### 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

b

• Given:

• a=3, b=3

• Find 

• Given:

• a=4, b=7

• Find 

• Given:

• a=5, b=8

• Find 

a

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

• qA=10C, qB=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