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Understanding Magnetism: From Poles to Fields and Induction

Explore the characteristics of magnets, magnetic poles, fields, and domains, as well as the practical uses of magnetic fields in electromagnets, speakers, motors, and electrical generators. Learn about producing electric current through electromagnetic induction and the different types of electromagnetic radiation in the EM spectrum.

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Understanding Magnetism: From Poles to Fields and Induction

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  1. Ch. 14 - Magnetism I. Characteristics of Magnets Magnetism Magnetic poles Magnetic field Magnetic domain

  2. A. Magnetism • Magnetism • force of attraction or repulsion between unlike or like poles • due to the arrangement of electrons • closely related to electricity

  3. B. Magnetic Poles • Magnetic Poles • like poles repel • unlike poles attract • a broken magnet creates new poles

  4. C. Magnetic Field • Magnetic Field • area around a magnet where magnetic forces act • field lines show direction of field (NS)

  5. D. Magnetic Domain • Magnetic Domain • groups of atoms with aligned magnetic poles domain • in a magnetized object, domains are all aligned

  6. Ch. 14 - Magnetism II. Uses of Magnetic Fields Electromagnet Speaker Motor

  7. 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

  8. B. Speaker • Speaker • electrical energy  mechanical energy • wire coil moves back & forth as its magnetic field interacts with the field of a fixed magnet • forced vibration causes the cone to move  sound

  9. C. Motor • Motor • electrical energy  mechanical energy • electromagnet rotates between the poles of a fixed magnet • commutator reverses the poles of the e’magnet

  10. armature & commutator assembled motor brushes & wires to battery field magnet C. Motor

  11. Ch. 14 - Magnetism III. Producing Electric Current Electromagnetic Induction Electric Generator DC & AC Transformer

  12. Coil Dynamic Microphone 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

  13. GENERATOR MOTOR B. Electric Generator • Electric Generator • mechanical energy  electrical energy • armature is rotated between magnet poles • magnetic field induces a current in the wire coil

  14. B. Electric Generator • Hydroelectric Dam • PE of lake water is converted to KE • mechanical KE turns the generator shaft which creates electrical energy

  15. 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

  16. 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

  17. D. Transformer • Step-up Transformer • increases the voltage • more turns • power plants • Step-down Transformer • decreases the voltage • fewer turns • household appliances (hairdryers, etc.)

  18. Ch. 15 - Light I. Electromagnetic Radiation • EM Radiation • EM Spectrum • Types of EM Radiation

  19. A. EM Radiation • Electromagnetic Radiation • transverse waves produced by the motion of electrically charged particles • does not require a medium • speed in a vacuum = 300,000 km/s • electric and magnetic components are perpendicular

  20. A. EM Radiation • Photons • tiny, particle-like bundles of radiation • absorbed and released by electrons • energy increases with wave frequency

  21. B. EM Spectrum long  low f low energy short  high f high energy

  22. C. Types of EM Radiation • Radiowaves • lowest energy EM radiation

  23. C. Types of EM Radiation • Radiowaves • FM - frequency modulation • AM - amplitude modulation • Microwaves • penetrate food and vibrate water & fat molecules to produce thermal energy

  24. C. Types of EM Radiation • Infrared Radiation(IR) • slightly lower energy than visible light • can raise the thermal energy of objects • thermogram - image made by detecting IR radiation

  25. R O Y G. B I V red orange yellow green blue indigo violet C. Types of EM Radiation • Visible Light • small part of the spectrum we can see • ROY G. BIV - colors in order of increasing energy

  26. C. Types of EM Radiation • Ultraviolet Radiation (UV) • slightly higher energy than visible light • Types: • UVA - tanning, wrinkles • UVB - sunburn, cancer • UVC - most harmful, sterilization

  27. C. Types of EM Radiation • Ultraviolet Radiation (UV) • Ozone layer depletion = UV exposure!

  28. C. Types of EM Radiation • X rays • higher energy than UV • can penetrate soft tissue, but not bones

  29. Radiation treatment using radioactive cobalt-60. C. Types of EM Radiation • Gamma rays • highest energy EM radiation • emitted by radioactive atoms • used to kill cancerous cells

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