Chapter 7 Static charge is produced by electron transfer

Electricity: Two Types  Static Electricity: (or static charge) refers to electric charges that can be collected and held in one place.  Current Electricity: the continuous flow of charge

Review from Unit 2  All matter is made up of atoms  The nucleus contains neutrons (no charge) and protons (positive charge)  The nucleus has a positive charge  Electrons (negative charge) are around the nucleus

Charges on objects can change  materials are charged with the transfer of electrons  The 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.

Positively Charged Negatively Charged Neutral

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 charge  Charged 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

Demonstration  The transfer and build up of charge 

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 objects  Rub 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 Technologies  Electrostatic 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 lightning If 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 Technologies  Photocopiers:  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 Electricity  Photocopy Technician  Linesman  Electrician  Engineer