Chapter 20, Section 1 Electric Charge and Static Electricity Wednesday, January 6, 2010 Pages

Objectives Describe the interaction of like and unlike electric charges. Define and describe static electricity and state how it differs from electric current. Describe lightning and other forms of static discharge.

Vocabulary Words Electric field Static electricity Conduction Induction Conservation of charge Static discharge Electroscope

Types of Electric Charge Charged parts of atoms are electrons and protons. Proton = positive (+) Electrons = negative (-)

Interaction Between Charges Charges that are the same repel each other. Charges that are different attract each other.

Electric Fields An electric field surrounds the charge -- it extends outward from every charged particle.  It is either pushed (if the 2 charges are the same) or pulled (if the two charges are different).

Electric Fields Around Single Charges Electric field lines are drawn with arrows to show the direction of the force on a positive charge. The EF is strongest where the lines are closest together (near the charged particle).

Electric Fields Around Multiple Charges The EF is altered when there are two or more charges. The EF due to the individual charges combine.

Static Charge Electrons are carried up a rubber belt and transferred to the metal sphere. The charge built up on the sphere is enough to send a spark several meters through the air. Van de Graaf generator

Charged Objects The buildup of charges on an object is called static electricity.  Charges build up but they DO NOT flow. Atoms in insulators hold their electrons tightly. Atoms in conductors hold some of their electrons loosely -- able to move freely.

Transferring Charge There are 3 methods by which charges are transferred:  Friction -- transfer of electrons from one object to another by rubbing.  Conduction -- transfer of electrons from one object to another by direction contact.  Induction -- movement of electrons to one part of an object caused by the electric field of another object.

Conservation of Charge Charges are not created. Charges are not destroyed. If one object gives up electrons, another object gains those electrons.  Electrons are only transferred from one location to another.

Static Discharge Defined as the loss of static electricity as electric charges move off an object.  When a negatively charged object and a positively charged object are brought together, electrons move until both objects have the same charge.

Electroscope This special instrument can detect electric charge.

Homework Workbook 20.1 (due 1/8) Worksheet 20.1 (due 1/7) Vocabulary quiz 20.1 (due 1/8)