electric charge ch 17.1 8th
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Information obtained from: Holt Science and Technology: Physical Science. New York: Henry Holt & Co, 2007. Print.TRANSCRIPT
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
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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
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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