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Transcript
Electricity and Magnetism Notes 6 Let’s Review • What makes up an atom? • Electron, Proton, Neutron • What charge does each have? • Electron – • Proton + • Neutron Neutral Let’s review some more! • There are three ways you can conduct a charge. Name the one that involves conducting a charge through rubbing? • Friction • Which one deals with being near the charged object? • Induction Again, Lets review! • Like charges ____________? • Repel • Unlike charges ____________? • Attract Still reviewing! • What is voltage? • The push of electrons. • What is current? • The flow of electrons. • What is resistance? • Holds back the current Reviewing… • What type of circuit is shown below? …Reviewing… • What type of circuit is shown below? Yes! • Now you will start writing the notes. • Look at your paper for AC and DC currents. • Let us begin. Direct Current • Direct current flows in one direction. • Can be produced using a solar cell or a chemical cell. A battery is a combination of chemical cells. DC Current • Electrons are repelled by the negative terminal of a battery and attracted to the positive terminal of a battery. • When a circuit is connected to the terminals the electrons will move from the negative terminal to the positive terminal. Alternating Current • AC current or alternating current moves back and forth. • Can be produced by a generator using the principle of electromagnetic induction. • The current is produced when a magnet moves relative to a coil of wire. AC Current • Electrons are repelled by the negative terminal and attracted to the positive terminal • Since the terminals are continually changing from positive to negative the current continually changes direction. Magnetism 1. force of attraction or repulsion between unlike or like poles 2. due to the arrangement of electrons 3. closely related to electricity Magnetic Poles • like poles repel Magnetic Poles • unlike poles attract Magnetic Poles • a broken magnet creates new poles Magnetic Field 1. area around a magnet where magnetic forces act 2. field lines show direction of field (NS) Magnetic Domain 1. groups of atoms with aligned magnetic poles Domain 2. in a magnetized object, domains are all aligned Electromagnets • Electric Currents in wires produce magnetic fields around the wire. • The magnetic field can be strengthened in several ways. A speaker uses electromagnets Electromagnet Electromagnets 1. Wrapping the wire in a coil. The greater the number of turns in the coil, the greater the increase in strength. 2. Adding a core. Iron vs. Al??? 3. Increasing the current in the coil will strengthen the electromagnet. Electric Motor Motors • Electric motors change electrical energy to mechanical energy. • Motors contain an electromagnet called an armature. • When an electric current runs through the wire in the armature it becomes magnetized. Motors • The armature spins because other magnets in the motor push and pull the armature and cause it to spin. • Motors use the magnetic force from magnets to spin an armature (magnetized by an electric current) • Where do we see motors? Generators • A generator changes mechanical energy into electrical energy. • Generators use electromagnetic induction to produce an electric current. Generators • When a wire or a coil of wire moves relative to a magnetic field and electric current can be produced. This process is called electromagnetic induction. Generators • In a generator at a power plant some other type of energy such as the energy in stream is used to turn a turbine which spins a magnet in a generator. • The magnet spins past a coil of wire. This moving magnetic field pushes electrons through the wire. Generators • A generator is similar to an electric motor. A generator is an electric motor working in reverse. • Generators produce AC current.