Chapter 7Static charge is produced by electron transfer

Electricity: Two TypesStatic Electricity: (or static charge) refers

to electric charges that can be collected and held in one place.

Current Electricity: the continuous flow of charge

Small Review from Unit 2All matter is made up of small particles called atomsThe center or nucleus of an atom contains neutrons

(no charge) and protons (positive charge)The nucleus has a positive chargeElectrons (negative charge) are around the positive

nucleusElectrons are smaller and can sometimes move

between atomic orbitalsProtons are larger and are found in the nucleus.

They do not move

Charges on objects can changeIn a solid material, only the electrons are able to moveSolid materials are charged with the transfer of

electronsThe friction between two objects can result in one

object losing electrons and the other object gaining electrons

Positive charge: if an object loses electrons (negative) it has more positive charge than negative so the object has an overall positive charge

Negative charge: if an object gains electrons (negative) it has more negative charge than positive so the object has an overall negative charge

Neutral: if an object has the same number of positive charges and negative charges.

Charges on objects can change

Acetate and paper towel are both neutral, but rub them together and paper towel loses electrons (overall positive charge) and the acetate gains electrons (overall negative charge)

Note: the number of charges drawn in the diagrams does not indicate the exact number of charges. They just represent the relative numbers.

Acetate

Paper Towel

An object can lose its chargeCharged objects, either negative or positive,

become neutral by attaching or touching a conductor to it.

The conductor transfers any excess static charge to the conductor (evenly spread over the conductor)

Grounding: connecting a conductor so that electric charge flows into Earth’s surface.

Electric Discharge: the removal of an electric charge from an object. Ex: Lightning, rubbing feet across carpet then touching a doorknob.

Static Electricity Activity

DemonstrationThe transfer and build up of charge

http://phet.colorado.edu/index.php

Unit of Measurement for electric chargeCoulomb: the unit of electric charge. 1

coulomb of charge equals the addition or removal of 6.25 X 1018 electrons.

This is about the number of electrons that pass through a 100 W light bulb per second.

Static Electricity and ForcesForce is defined as a push or pull

Electric force: is a push or pull between charged objects

The electric force is an example of an “action at a distance force” – A force can be applied to an object without touching it

Laws of Electric Charges (Static Charge)Like charges repel (push apart)Opposite charges attract (pull together)

Laws of Electric Charges…Some Neutral objects are attracted to

charged objectsRub a balloon with your hair, the balloon will

pick up electrons and become negatively charged.

It will be attracted to the neutral wall

Static Knowledge and TechnologiesElectrostatic air cleaners: removes

electrons from particles in the air and the charged particles are then attracted to a plate on the device

Lightning Rods: Placed on top of a building and it protects the building from lightningIf lightning occurs near the building the large

amount of charge will pass through the lightning rod to the ground rather than the building.

Static Knowledge and TechnologiesPhotocopiers:

light hits paper and reflects off white part of the copier

Reflected light hits drum and removes static charges in this area

Neutral Toner goes over drum and sticks to charged area.

Paper rolls over the drum and it has stronger attraction for the toner. Toner is now “baked” on the paper

Careers related to ElectricityPhotocopy TechnicianLinesmanElectricianEngineer