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Electric Chargeand
Electric Field
Write at least three questions that you have about ELECTRICITY.
QuestionsWhat causes electricity?Why is electricity harmful? How much is
lethal?What is the difference between static
electricity and current electricity?What makes electrons move?What is the difference between an amp and
a volt?What makes a conductor conductive?
Questions1. T or F, Electric charges behave just like
magnets in that they only repel each other.
VocabularyElectrostatics
Electric Charge
Neutral
Insulator
Conductor
Charging by induction
Law of conservation of charge
Coulomb’s law
Elementary charge
Electrons
Permittivity of free space
Principle of superposition
Electric field
ReadingChapter 16, Electric Charge and Electric Fields
Electrostatics
Study of electrical charges collected and held in one place
Examples
Static electricity from the clothes dryer
Static electricity from combing your hair
Where does charge come from?
Conductors and Insulators
Elementary ChargeOne electron has a charge of
1.602 x 10 -19 Coulombs
One coulomb is the charge on 6.25 x 10^18 electrons
A large lightning bolt is about 10 coulombs
Conservation of Charge
CHARGE
Can be transferred
Cannot be created or destroyed
Electric ChargeLike charges repel. Opposite charges attract.
Separation of ChargeAn electroscope can be used to detect the presence and relative amount.
Charging by Induction
Coulomb’s Law
Click image to view movie.
Coulomb’s Law•Used to calculate the magnitude of electric force•Inverse square law
Similarities Between Coulomb’s Law and Newton’sLaw of Universal Gravitation
Inverse Square Laws
Forces on Charges
Coulomb’s LawTwo balloon’s are located 15 cm apart. Each
balloon holds a charge of +6.0 μC.
Calculate the electrostatic force is exerted by each balloon.
Superposition of Forces- Find force on charge A
Example Problem: Determining the Total Force Exerted on the Positive Charge
Electric FieldsHow can you tell that Earth has a
Gravitational Field?
Electric Fielda region around a charged object where the object’s electric
force is exerted on other charged objects.
Electric Field• The strength of an electric field is equal to the
force on a positive test charge divided by the strength of the test charge.
• The direction of an electric field is the direction of the force on a positive test charge.
• A test charge always must be small enough so that its effect on “Q” is negligible.
• The magnitude of the electric field strength is measured in Newtons per coulomb, N/C.
Example Problem- Electric FieldA positive test charge of 3.0 x 10-6 C experiences a force of
0.12 N at an angle of 15º north of east. What are the magnitude and direction of the electric field at the location of the test charge.
Drawing Electric FieldsAn electric field is a region around a charged object where the object’s electric force is exerted on other charged objects.
Electric Fields
Additional Resources
Use Electricity and Magnetism CD
Use www.falstad.com
Quiz- Draw the Electric Field1. A positive charge
2. A negative charge
3. One positive and one negative charge of equal magnitude
4. Two positive charges of equal magnitude
5. Two negative charges of equal magnitude
6. One positive and one negative charge of unequal magnitude
7. Two positive charges of unequal magnitude
8. Two parallel plates with opposite charges
Superposition of E-fields
E = E1 + E2 + E3
E = F/q = F1/q +F2/q +F3/q
Van de Graaff Generator
HomeworkPhysics: Principles and Problems, Glencoe
Electric Charge
Chapter 20, p558-559, #23-28, 30, 34-36, 41-43, 49, 51
Electric Field
Chapter 21, p.585-587, #67, 71, 73, 74
AP Physics
Additional Slides
JJ Thompson’s Experiment
Rutherford’s Gold Foil Experiment
Transferring Charge
There are three methods by which charges can be transferred to build up static electricity: charging by friction, by conduction, and by induction.
Electric ForceAn electric field is a region around a charged object where the object’s electric force is exerted on other charged objects.
Lightning
Click the Video button to watch a movie about lightning.
Electric ForceAn electric field is a region around a charged object where the object’s electric force is exerted on other charged objects.