Ch. 8 - Magnetism I. Characteristics of Magnets  Magnetism  Magnetic poles  Magnetic field  Magnetic domain

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Ch. 8 - Magnetism I. Characteristics of Magnets Magnetism Magnetic poles Magnetic field Magnetic domain Slide 2 A. Magnetism Magnetism force of attraction or repulsion between unlike or like poles due to the arrangement of electrons closely related to electricity Slide 3 B. Magnetic Poles Magnetic Poles like poles repel unlike poles attract a broken magnet creates new poles Slide 4 C. Magnetic Field Magnetic Field area around a magnet where magnetic forces act field lines show direction of field (N S) Slide 5 Slide 6 D. Magnetic Domain Magnetic Domain groups of atoms with aligned magnetic poles in a magnetized object, domains are all aligned domain Slide 7 Strength of magnets and magnetic fields Attraction and repulsion of magnets increases as they get closer to one another and decreases as they get farther apart. Magnetic fields are strongest at the poles. Slide 8 Permanent magnets Not all metals can become magnetic. Aluminum foil for instance, does not. Iron, cobalt and nickel are the only metals that can become magnets. Permanent magnets are created when these metals are placed within a strong magnetic field. Slide 9 Loss of magnetism Permanent magnets can lose their magnetism when heated or when they suffer a large impact. Slide 10 Ch. 8 - Magnetism II. Uses of Magnetic Fields Electromagnet Speaker Motor Slide 11 A. Electromagnet Electromagnet strong, temporary magnet formed when current is passed through a coil of wire surrounding an iron core acts like a bar magnet when current is on Slide 12 B. Speaker Speaker electrical energy mechanical energy wire coil moves back & forth as its magnetic field interacts with a fixed magnet forced vibration causes the cone to move sound Slide 13 C. Motor Motor electrical energy mechanical energy electromagnet rotates between the poles of a fixed magnet commutator reverses the poles of the emagnet Slide 14 C. Motor brushes & wires to battery field magnet armature & commutator assembled motor Slide 15 D. Galvanometers Devices that use electromagnets to measure electric current (ex. sensors or gauges in your car. Slide 16 Ch. 8 - Magnetism III. Producing Electric Current Electromagnetic Induction Electric Generator DC & AC Transformer Slide 17 A. Electromagnetic Induction Electromagnetic Induction producing a current by moving a wire through a magnetic field some microphones work just like mini- speakers in reverse sound waves cause coil to move current Dynamic Microphone Coil Slide 18 B. Electric Generator Electric Generator mechanical energy electrical energy armature is rotated between magnet poles magnetic field induces a current in the wire coil MOTOR GENERATOR Slide 19 B. Electric Generator Hydroelectric Dam PE of lake water is converted to KE mechanical KE turns the generator shaft which creates electrical energy Slide 20 C. DC & AC Direct Current (DC) current flows in one direction dry cells Alternating Current (AC) current reverses its direction at regular intervals electrical outlets Slide 21 D. Transformer Transformer increases or decreases AC voltage primary coil AC produces a magnetic field that induces AC in the secondary coil voltage ratio = ratio of turns in each coil Slide 22 D. Transformer Step-up Transformer increases the voltage more turns power plants Step-down Transformer decreases the voltage fewer turns household appliances (hairdryers, etc.)

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