Download Magnetism: Book ch 36

AC/DC/e-m quiz
Review all 4 ppts on my website: AC/DC, ACpower awesome,
electricity and magnetism, AC DC Tesla
Book work:
AC/DC
 Ch 34: rev questions 18-25
E-M
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Ch 36, sections 1-5, 9:
o rev questions 1-5, 10, 11,19
1. They attract and repel one another
2. Can isolate or separate charges, not poles
3. Space around magnet or moving charges that can exert a force; source is moving electrons
4. Electrons spin in opposite directions, fields cancel
5. Fields of iron’s electrons do not cancel entirely
10. Concentric circles
11. Fields overlap, add up as vectors inside the loop, they can partially cancel outside the loop
19. Currents in the earth’s molten layer
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o think & explain 1, 5, 9
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1. Electric field surrounds any electric charge; electric AND magnetic field surrounds a
moving charge
5. Question relates to the electromagnet used in scrapyards to move junk cars and scrap
metal: iron inside the coil or loop may be a magnet already or becomes magnetized when
the current in the coil around it is turned on; it multiplies, increases the mag field from
the coil alone
9. Pigeons can sense the earth’s magnetic field
Ch 37, sections 1-6:
o rev questions 1-3, 7-10, 14, 17, 18
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1. Magnet in motion can induce voltage, current in a wire
2. Wire and magnet must be in relative motion; the magnetic field must be changing!
3. More loops, more voltage, current induced
7. Generator requires mechanical energy or work in to transform into electrical energy
Motor takes electrical energy, transforms into mechanical energy
9. What causes rotation of the coil/magnet? Work by some external method such as
spinning turbines using wind, water, combustion of fossil fuels
10. 3 main ingredients of motor are same as for generator: magnetic field, moving
charges, magnetic force.
14. Ste-up transformer steps up VOLTAGE
17. Power in = power out, IV in = IV out, if no energy, power losses
18. High voltage = lower current = lower power losses over long distances
o think & explain 8-11
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8. If you move a magnet so that it doesn’t change the field through the cross
section of the coil/loop
9. Transformer needs AC because AC provides the changing magnetic field
needed to induce a voltage, current in the other part of the transformer
10. Transformer can produce more energy than goes in, power in= power out of
100% efficient, can’t step up energy, goes against conservation of energy
11. Can’t connect motor to generator in a closed circuit and expect it to run
forever = perpetual motion machine, there will be losses due to < 100 % eff,
Light quiz
Review waves, light ppts and documents on my website
Please check the ‘light lab’ document on my website. It lists relevant sections in the
book for each of the 11 labs we did.