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Ch 21-Magnetism

Ch 21-Magnetism. Magnetism. a property of matter in which there is a force of attraction or repulsion between like and unlike poles. Magnetic Poles. force is strongest at the magnetic poles: North & South Like poles repel, unlike attract. Force of attraction decreases as distance between

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Ch 21-Magnetism

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  1. Ch 21-Magnetism

  2. Magnetism a property of matter in which there is a force of attraction or repulsion between like and unlike poles

  3. Magnetic Poles force is strongest at the magnetic poles: North & South Like poles repel, unlike attract

  4. Force of attraction decreases as distance between • magnets increases

  5. If a bar magnet is suspended so it turns freely (like a compass), it will point magnetic N

  6. Permanent Magnets made from iron-Fe,cobalt-Co,or nickel-Ni (aka the IRON TRIAD) retain magnetic properties for a long time

  7. Temporary Magnets happens when object is near or is touching a magnet lose magnetic properties soon after they are separated from a magnet

  8. Magnetic field area around the magnet where forces act

  9. Magnetic domains groups of atoms w/ aligned magnetic poles

  10. magnets can lose some magnetic properties if dropped or heated “drop it like it’s hot”

  11. if a magnets breaks, you have lots of little magnets

  12. Star questions • What is a force of attraction or repulsion between like and unlike poles? • Magnetism • Where is this force the strongest? • The poles • What is the Iron Triad? • Iron, Cobalt, Nickel; only elements to form permanent magnets • What are groups of atoms with aligned magnetic poles? • Magnetic Domains • How can a magnet loose some of its magnetic properties? • Heat it or Drop it

  13. Uses of Magnetic fields Hans Christian Oersted – observed that a current moving through a wire moved the needle on a nearby compass; moving electric charges create a magnetic field.

  14. Uses of Magnetic fields Solenoid – coil of current-carrying wire that produces a magnetic field

  15. Uses of Magnetic fields Electromagnet – strong, temporary magnet made by inserting an iron core into a wire coil & passing an electric current through the coil.

  16. Strength of electromagnet can be increased by: inserting iron core adding more turns to the wire increasing the amount of current

  17. Electromagnetic Devices • Electromagnets change electrical energy to mechanical energy Motor using an electromagnet to turn an axle

  18. Commutator – • reversing switch

  19. Electromagnetic Devices Galvanometer – detects electric current, using a solenoid

  20. Generating Electric Current • Michael Faraday discovered electromagnetic induction; according to his law, a voltage is induced in a conductor by a changing magnetic field

  21. Electromagnetic induction

  22. Generating Electric Current Generators – produce electric current by rotating a loop of wire in a magnetic field.

  23. Generators Mechanical energy produces electrical energy

  24. FORCE • Movingelectric chargesproducemagnetic force • Movingmagnetsproduceelectric force

  25. Two types of generators Direct current (DC) - current flows in one direction, example is dry cell batteries Alternating current (AC) - current reverses direction in a regular pattern

  26. 1. Step-up Increases voltage More coils in secondary coil 2. Step-down Decreases voltage More coils in primary coil Transformers

  27. Transformers

  28. Voltage converters like in USA, Europe, Asia, Africa, Australia

  29. Superconductors Material that has no electrical resistance Occurs at OK Advantages current flows indefinitely eliminates electrical waste Disadvantages brittle, hard to shape into wires need to be cold in order for it to work

  30. LAST Star questions • Reversing switch • Commutator • Compasses point here • Magnetic north • A transformer that increases voltage • Step-up transformer • Material which has no electrical resistance • Superconductor • STUDY VOCABULARY!!!!!

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