Electric Charge and Electric Field

Write at least three questions that you have about ELECTRICITY.

Questions What 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?

Questions 1.T or F, Electric charges behave just like magnets in that they only repel each other.

Vocabulary Electrostatics 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

Reading Chapter 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 Charge One electron has a charge of x 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 Charge Like charges repel. Opposite charges attract.

Separation of Charge An 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’s Law of Universal Gravitation

Inverse Square Laws

Forces on Charges

Coulomb’s Law Two 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 Fields How can you tell that Earth has a Gravitational Field?

Electric Field a 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 Field A positive test charge of 3.0 x 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 Fields An 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

Quiz- Draw the Electric Field 1. 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 = E 1 + E 2 + E 3 E = F/q = F 1 /q +F 2 /q +F 3 /q

Van de Graaff Generator

Homework Physics: Principles and Problems, Glencoe Electric Charge Chapter 20, p , #23-28, 30, 34-36, 41-43, 49, 51 Electric Field Chapter 21, p , #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 Force An 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 Force An electric field is a region around a charged object where the object’s electric force is exerted on other charged objects.