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demos. Intro: electricity is gonna be big. Ac/Hon Physics Notes. Chapter 20 Electostatics. Lesson 1 Definitions and concepts. Objectives. At the end of this lesson you will be able to: Define electric charge and explain how forces act between charged objects. Electricity!.
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demos • Intro: electricity is gonna be big
Ac/Hon Physics Notes Chapter 20 Electostatics
Objectives • At the end of this lesson you will be able to: • Define electric charge and explain how forces act between charged objects
Electricity! • Electricity: • Flow of electrons • Electrostatics • Study of electrons (and protons) standing still
The Atom and Electric Charges • Electrons • Negative charge • Protons • Positive charge
Electrostatic Force • Like charges repel each other • Unlike charges attract each other • The attraction or repulsion is called: • Electrostatic Force • It is a force like all other forces we’ve studied in this class • Units = ?? • Newtons
Other fun facts • All Electrons and protons are the same regardless of what kind of atom
Questions • What is electric charge? • What causes electrostatic force? • Why do like charges repel and vice versa? • Electrostatic Force Stop asking so many questions. We have no idea. Just accept it
How do we measure electric charge? • Coulombs (C) • Charles-Augustin de Coulomb (1736-1806) • Charge of an electron or proton e = 1.602 × 10-19C + for proton • for electron • How do we get more charge (more Coulombs)? • Add more electrons or protons • Wait – do we ever add protons? We’ll get to this later….
What is the electrical charge of an atom? • Zero • It has the same # of protons and electrons • Zero charge Charge Neutral
How do we give something a charge? • Add or take away electrons • Protons don’t move • Adding electrons • Gives negative charge • Removing electrons • Gives positive charge • Atoms with a missing OR extra electron are called: • Ions
Conductors and Insulators • Conductors • Electrons move easily through • Insulators • Electrons stay put
Charge Conservation • Electrical charge can never be created or destroyed • It only moves
Objectives • At the end of this lesson you will be able to: • Solve problems involving moving of charge
Objectives • At the end of this lesson you will be able to: • Solve problems involving moving of charge
Ways things get charged • Conduction • 2 things touch and electrons move • Induction • 2 things come close to each other and electrons get pushed or pulled – we’ll explain this more soon…
What electrons like to do • If there is no force on them, electrons spread out evenly
What’s up with “Ground” • Earth is big • It has a lot of electrons – really a lot • If a charged object comes in contact with the earth, it automatically becomes neutral • We say this object has been “grounded” • Explain why…
Charging Problems • Do on board • A charged object comes in contact with a charge neutral object (pos and neg) • A charged object come near a charge neutral object that’s grounded and the ground is removed.
Why will a charged object attract a charge neutral object like in the paper and ruler demo • Do on board
Electorsopes • A tool that tells you when it is charged. • Do on board
Objectives • At the end of this lesson you will be able to: • Apply Coulomb’s Law
Coulomb’s Law • Tells us how big the force is between 2 charged objects (let’s call them A and B • Where F is the force (same on and B but opposite directions) • K = 9.0 x 109 Nm2/C2 • qa and qb are the charges of A and B respectively • r is the distance between the charges