Chapter 17 Section 1

Describe how charged objects interact by using the law of electric charges

Describe 3 ways in which an object can become charged

Compare conductors with insulators

Give 2 examples of static electricity and electric discharge

To say that something is “charged” is not entirely accurate.

Objects that we call charged actually have a charge imbalance; they have an unequal number of protons and electrons

All matter is made up of tiny particles called atoms

Atoms are made of protons, neutrons, and electrons

Protons and electrons are charged, neutrons are not

Charge is physical property

Charge can be positive (+), negative (-) or neutral (no charge)

Charged objects exert a force (push or pull) on other charged particles

Law of Electric Charges: like charges repel (push away), opposite charges attract.

http://boguta.phy.uic.edu/courses/physics107/lectures/Week5F/Lecture11/HTMLFiles/index_1.gif

Electrons are held in atoms because of the charge between protons (+) and electrons (-)

http://www.elmec.com.my/electricity.jpg

The charge between objects is an electric force

The size of the force depends on: The amount of charge on each object (greater

charge = greater force) Distance between the charges (closer = greater)

Electric Field: the region around a charged object in which an electric force is exerted on another charged object

http://www.dannex.se/theory/pict/image122.gif

Atoms have equal numbers of protons and electrons

The positive and negative charges cancel each other out, therefore atoms do not have charge

Objects can become charged by: Friction, Conduction, and Induction

Electrons are “wiped” from one object to another

Ex: Wiping a plastic ruler with a cloth electrons move from the cloth to the ruler the ruler gains electrons and becomes

negatively charged The cloth loses electrons and becomes

positively charged

http://www.ncert.nic.in/html/learning_basket/electricity/animations/magnetic_girl.gif

When electrons move from one object to another by direct contact

Ex: Touch an uncharged piece of metal with a (+) charged glass rod Electrons from the metal will move to the glass

rod Metal loses electrons and becomes (+) charged

http://image.tutorvista.com/content/static-electric-current/charging-by-conduction.jpeg

Charges in an uncharged metal object are rearranged without direct contact with a charged object

Ex: Hold a metal object near a positively charged object Electrons in the metal are attracted and move

toward (+) charged object The movement causes (induces) an area of (-)

charge on the surface of the metal

http://www.physicsclassroom.com/class/estatics/u8l2b5.gif

No charges are created or destroyed

Simply move from one atom to another

Electroscope: a device used to see if something is charged

Glass flask, metal rod, rubber stopper, 2 metal leaves

When not charged leaves hang down; charged – spread apart

Cannot tell if the object is (+) or (-) charged

http://www.teclas.org/chispas/images/electroscope1.gif

Electric charges move through some materials more easily than they move through others

Most materials are either conductors or insulators based on how easily charges move through them

The electric charge at rest on an object

Static = not moving

Ex: clothes in the dryer

http://thatcostumegirl.com/gallery/d/2578-2/scling.jpg

http://4.bp.blogspot.com/_SvWmSsc4HlM/SxKkgzTcS_I/AAAAAAAACsA/Y43mxF6WMSk/s1600/Static+electricity

Charges that build up eventually leave the object

Electric Discharge: the release of electricity stored in a source

Can happen slowly or quickly (lightning)

http://www.severewx.com/reports/lightningsources.gif

Strikes the highest point in a charged area (shortest path)

Bad places to be in a storm: Golf course Beach Under a tall tree

Pointed rod connected to the ground with wire

When joined to the Earth by a conductor (wire) are said to be grounded

Provides a path for electric charges to move to the Earth where charges can be absorbed

http://www.elliottelectric.com/References/images/residentiallightning.gif

Briefly explain the relationship between charge and force

Discuss the difference between and electrical conductor and an electrical insulator. Give an example of each