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Physics Electricity and Magnetism Overview • Begin Static Electricity – – – Electric charges Electric forces Fields Physics Electric and Magnetic Phenomena California State Standards Physics: Electric and Magnetic Phenomena 5. Electric and magnetic phenomena are related and have many practical applications. As a basis for understanding this concept: a. Students know how to predict the voltage or current in simple direct current (DC) electric circuits constructed from batteries, wires, resistors, and capacitors. b. Students know how to solve problems involving Ohm’s law. V =IR (voltage = current x resistance) California State Standards c. Students know any resistive element in a DC circuit dissipates energy, which heats the resistor. Students can calculate the power (rate of energy dissipation) in any resistive circuit element by using the formula Power = IR (potential difference) ×I (current) = I2R. d. Students know the properties of transistors and the role of transistors in electric circuits. Transistors are switches used to amplify a signal. e. Students know charged particles are sources of electric fields and are subject to the forces of the electric fields from other charges. California State Standards f. Students know magnetic materials and electric currents (moving electric charges) are sources of magnetic fields and are subject to forces arising from the magnetic fields of other sources. g. Students know how to determine the direction of a magnetic field produced by a current flowing in a straight wire or in a coil. h. Students know changing magnetic fields produce electric fields, thereby inducing currents in nearby conductors. i. Students know plasmas, the fourth state of matter, contain ions or free electrons or both and conduct electricity. California State Standards j.* Students know electric and magnetic fields contain energy and act as vector force fields. k.* Students know the force on a charged particle in an electric field is qE, where E is the electric field at the position of the particle and q is the charge of the particle. l.* Students know how to calculate the electric field resulting from a point charge. m.* Students know static electric fields have as their source some arrangement of electric charges. California State Standards n.* Students know the magnitude of the force on a moving particle (with charge q) in a magnetic field is qvB sin(a), where a is the angle between v and B (v and B are the magnitudes of vectors v and B, respectively), and students use the right-hand rule to find the direction of this force. o.* Students know how to apply the concepts of electrical and gravitational potential energy to solve problems involving conservation of energy. Van de Graaff Generator (It’s Alive!) schematic of a Van De Graaf Generator Nicola Tesla Electric Force Is Way Stronger Than Gravitational Force • Electric Force Fe = k q1 x q2 / d2 (k = 9.0 x 109 N m2 / C2) • Gravitational Force Fg = G m1 x m2 / d2 (G = 6.7 x 10-11 N m2 / kg2) • Most things are electrically neutral (balanced) – Same number of electrons and protons Atoms An atom is made up from three things: 1. Electrons – – – They are the particle that moves They have a negative electric charge (“-” or “-1”) They are not very heavy They circle around outside of the nucleus (center of the atom) Electrons Atoms An atom is made up from three things: 2. Protons • • They have a positive electric charge (“+” or “+1”) They are much heavier than the electrons • They are in the nucleus • They are just like protons except they have no electric charge (“0” zero) (1 proton “weighs” as much as 1800 electrons) 3. Neutrons Nucleus (Protons and Neutrons) Ionic Bonds (Exchange) Li Lithium wants to give away its electron. F Fluorine wants to get an extra electron. - Cation The oppositely charged ions attract Anion + Li F Electric Fields Electric Fields Interact • Like charges repel, opposites attract Charge by Conduction (conduction: by touching) Charge by Induction (Induction: by being near) Induced Charge in Insulators