CHAPTER 8:

1. CHAPTER 8: MAGNETISM

2. 1) Magnetite is odd because when it swings freely, the same part would always face in the same direction. It's a natural magnet.

3. 2) It gets its name from the Greeks living in Magnesia.

4. 3) Magnetism=force of attraction or repulsion due to an arrangement of electrons.

5. 4) Magn. field-region in which magnetic forces can act5) Mag. lines of force--define the magnetic field of an object. 6) mag. pole--ends of magnet where mag. force is greatest.

6. 7) straight bar of iron

7. 8) N. mag pole--end of mag. that points N  S. mag pole--end of mag. that points S9) Rule: like poles repel, opposites attract10) Nat. mag--naturally occurring substance that has mag. poles

8. 11) mag. domain--region in which mag. fields of atoms are grouped together. If not "in line"--unmagnetized.

9. 12) Temp. mag--materials that are easy to magnetize but lose magnetism quickly (soft iron).Perm. mag--made of materials harder to magnetize, but tend to stay magnetized.

10. 13) Cobalt, nickel, iron are materials from which strong perm. mags can be made.

11. 14) Hans Christian Oersted--in 1820, discovered electromagnetism by accident--was lecturing to physics class, noticed wire lying above compass, observed that when current flowed thru wire, needle was deflected, when current was reversd, needle moved in opposite direction, no electricity flowed, no movement by needle

12. 15) EM--relationship between electricity and magnetism16) Electromagnet: made by wrapping coil of wire around soft iron core and passing an electric current thru the wire. Strength decreases/increases dep. on # of loops of wire. Also it's stronger if the current is higher/stronger.17) Lose properties by turning current off. Gain properties by turning current on.

13. 18)motor: converts elect. energy into mech. energy  commutator: has special reversing switch that runs on DC, switches the direction of the current so that the mag. poles of the EM reverse and the EM spins  solenoid: wire wrapped into a cylindrical coil  galvanometer: used to detect small current

14. 19) EM induction: process by which a current is produced by the motion of a conductor in a mag. field; involves mag. lines of force.

15. 20) generator: converts mech. energy into electric energy

16. 21) increases or decreases voltage of AC22) primary and secondary23) step up: increases voltage    step down: decreases voltage

17. 24) Yes, opposites attract, likes repel.25) AlNiCo--makes very strong magnet--out of aluminum, nickel cobalt and iron

18. 26) 1600--William Gilbert-proposed idea that earth itself is a magnet; predicted earth would be found to have mag. poles.27) Earth behaves as magnet: it exerts mag. forces on magnets, compasses and is surrounded by a mag. field that is strongest near the N and S magnetic poles

19. 28) region of earth's mag field

20. 29) helps find direction based on earth's mag field; needle always pts N.Compass points to mag poles, not geographic poles--Mag N pole--NE Canada, abt 1600km from GNP; Mag S pole--Antarctic Circle30) magnetic variation: error in compass caused by it reading the magnetic N instead of the geographic N.

21. 31) Magnetism is due to the motion of the electrons, particularly their spin. 32) Michael Faraday: said an electric current could be generated/induced by moving a wire thru a mag field.