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Magnetism

Magnetism. Chapter 21 Prentice Hall 2006. 21.1&2 Magnetism & Electromagnetism. Define vocabulary terms in 21.1-3 (15) Write the key concepts in 21.1-3 (10) 651/1-10 (complete sentences), 14, 15,17, 30 Workbook pages: 251-258. 21.1&2 Magnetism & Electromagnetism. Review:

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Magnetism

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  1. Magnetism Chapter 21 Prentice Hall 2006

  2. 21.1&2Magnetism & Electromagnetism • Define vocabulary terms in 21.1-3 (15) • Write the key concepts in 21.1-3 (10) • 651/1-10 (complete sentences), 14, 15,17, 30 • Workbook pages: 251-258

  3. 21.1&2Magnetism & Electromagnetism Review: 1. Like magnetic poles _____ 2. Unlike magnetic poles ____ 3. Magnetic field lines run from ___ to ___

  4. answers • Like poles repel • Unlike poles attract • Magnetic field flows from N to S

  5. Earth’s Magnetic Field

  6. Electricity can produce magnetism and … • Magnetism can produce electricity!!! • When electricity flows through a conductor, a magnetic field is produced • Right hand rule for a straight conductor

  7. 21.3 Electrical Energy Generation and Transmission • When a coil of wire moves in a magnetic field, electricity will flow in the coil (aka: electromagnetic induction) • This is how our electricity is generated • Faraday’s Law - an electric current can be produced in a circuit by a changing magnetic field.

  8. Right hand rule used in designing and understanding of generators I current flow B magnetic field direction F resulting force acting on wire

  9. Faraday’s Law • Just by moving a magnet in a coil of wire or [as in fig. (c), the switch is turned on or off] electricity is produced. This is how electricity is generated.

  10. Transformers These change the voltage and current of electricity by having different numbers of turns on the primary and secondary coils Before electricity gets to your house it is stepped down by a passing through a step-down transformer.

  11. Transformer Formula • TurnsSecondary = VoltageOutput • TurnsPrimaryVoltageInput • If you know three things out of 4, you can solve for the 4th. Like a proportion in math!

  12. Transformer Problem: • The input voltage from a generating plant to a transformer is 11,000 v. If the output voltage from the transformer is 240,000 v, what is the ratio of secondary to primary turns in this stepup transformer? • TurnsSecondary = VoltageOutput • TurnsPrimaryVoltageInput • 240,000 v = 240 = 21.8 • 11,000 v 11

  13. Another problem… • A step-down transformer has 360 turns of wire in its primary coil. How many turns are in the secondary coil if the input voltage = 120 V, and the output voltage is 10 V? • TurnsSecondary = VoltageOutput • TurnsPrimaryVoltageInput • TS= Vout TP = 10 V (360 turns) = 300 turns • Vin 120 V

  14. The stronger the magnetic force of a magnet, the more effect it has on another magnetic or on moving charges Magnetic fields are produced by moving electric charges AC and DC generators are similar except DC generators use commutators to produce direct current Heat from fossil fuels spins a turbine (coil of wire that spins in a magnetic field) that generates electrical energy More ElectroMagnetic Information

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