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Chapter 22 Magnetism and its Uses

Chapter 22 Magnetism and its Uses. Objects. 22.1 Describe the properties of magnets 22.1 Define the region of force around a magnets 22.1 Model magnetic behavior using domains. Objects. 22.2 Explain the magnetic effects of a current in a wire

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Chapter 22 Magnetism and its Uses

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  1. Chapter 22 Magnetism and its Uses

  2. Objects • 22.1Describe the properties of magnets • 22.1 Define the region of force around a magnets • 22.1 Model magnetic behavior using domains

  3. Objects • 22.2Explain the magnetic effects of a current in a wire • 22.2 Compare and contrast ammeters and voltmeters • 22.2 Describe the function of an electric motor.

  4. Objects • 22.3Describe how a generator produces an electric current using electromagnetic induction • 22.3 Distinguish between alternating and direct current • 22.3 Explain how a transformer can step up or step down the voltage of an alternate current

  5. Objectives • 22.4 Describe the characteristics of superconductors • 22.4 Consider various applications of superconductivity

  6. Key Words • Magnetism Magnetic Pole Magnetic Field • Magnetic Domain Electromagnet Ammeter • Voltmeter Electric Motor • Electromagnetic Induction • Generator Direct Current Alternating current • Transformer Solenoid

  7. Magnetism • Magnetism is a property of matter in which there is a force of attraction or repulsion between unlike or like poles • One positive end, one negative end • Most metals area actually NOT magnetic • Iron, Cobalt and Nickel metals which are actually magnetic • Other metals can be temporary magnets

  8. Opposites Attract

  9. The Earth • Earth is a big magnet. The actual location of the magnetic poles change every year by about 40 miles • Earth’s magnetic poles change yearly

  10. Magnetic Declination • Your compass points to the magnetic pole, not to the true north pole • As you approach the poles, you have to add/subtract degrees to go the right direction • Compass is wrong close to poles

  11. The north arrow on the compass rose (the large N) is pointed towards the place on the horizon directly beneath the North Star! That is, towards true north! • And the needle (of course) points towards magnetic north! So the magnetic declination for this locality is 45 degrees west

  12. Magnetic Domains • Groups of atoms with aligned magnetic poles are called

  13. Magnetic Fields • Points towards the South Pole • So, South must be Negative end • Since magnetic fields point towards the negative charge • Magnetic Pole: End of magnet, strongest magnetic field • Earth’s North pole • Is the south magnet

  14. Electromagnet • A type of magnet created by current passing through a coil • Electromagnetic Induction: The process by which moving a wire through a magnetic field produces a current

  15. Solenoid: Coils wrapped around with a current moving through. Used in MRI’s

  16. Thumb points towards the North End

  17. Magnetic Field Force • The current causes the magnetic field • The magnetic field in turns pushes on the wire • Electric Motor: Turns electrical energy into mechanical energy

  18. Reading Current and Voltage • Voltmeter: Determines the voltage drop across a resistor • Ammeters: Determine the current through a wire • Determined by deflection caused by the magnetic field

  19. Generator • Produces electric current by rotating wires in a magnetic field • See simulator

  20. Direct Current • DC = Direct Current. The flow (current) of electrons is in one direction • Like a river runs only down hill, direct current only flows one way. • Batteries provide this type of current

  21. Alternating Current • AC = Alternating Current Electrons flow back and forth. The electrons are pushed one way, then pushed the other way. • The electrons stay in roughly the same area, just going back and forth. Our outlets provide this, alternating current.

  22. Alternating Current • In the USA, there are three wires that transmit the flow of energy. • Two are at + or – 120 Volts (180 degrees out of phase) • One is at 0 Volts • The US has adopted a frequency of 60 Hz • The polarity (direction of electrons) changes 120 times per second • Actual voltage of peaks are + and – 170 volts

  23. Transformers • A transformer is just a piece of iron with a pair of wires coiled around it - one with many more turns in the coil than the other. • The coils of wire are not physically connected. The iron core is immersed in an insulating oil bath which does not conduct electricity well. • Step Up or Step Down the Voltage

  24. Transformers

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