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Title:

Electricity and Magnetism CRCT review

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Title: Chapter One Notes Author: Veronica S. Cook Last modified by: Veronica Created Date: 8/9/2004 2:05:28 AM Document presentation format: On-screen Show – PowerPoint PPT presentation

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Title: Electricity and Magnetism CRCT review


1
Electricity and Magnetism CRCT review
2
just like gravity
  • A force that depends on
  • Size (mass or charge of objects)
  • Distance between the centers

3
What particle?
  • carries positive charge in the atom? Where is
    it?
  • carries negative charge in the atom? Where is
    it?
  • has no charge in the atom? Where is it?

4
static electricity
  • Electric charges are separated. More of either
    protons or electrons in one place.
  • How? Move electrons

5
Ways to move electrons
  • friction rub them from one object to another
  • conduction electrons flow from touching objects
  • induction electrons move in response to
    electric field without objects touching

6
Electric current
  • What is electric current?
  • What does an electric current cause?
  • What is caused when the current is changing?

7
magnets
  • Electrons with same spin line up and create
    magnetic domains.
  • Permanent magnets lots of aligned domains
  • Cobalt, nickel and iron make good permanent
    magnets.

8
magnetic properties
  • Always has both north and south pole
  • Cut in half two whole magnets

9
Earths magnetic poles
http//hyperphysics.phy-astr.gsu.edu/ hbase/magnet
ic/imgmag/mearthbar.gif
10
solenoid
  • Coil of wire

11
electromagnet
  • solenoid wrapped around an iron core
  • The magnetic field inside iron magnifies the
    solenoids field

http//hyperphysics.phy-astr.gsu.edu/hbase/magneti
c/imgmag/sol3.gif
12
Stronger electromagnet
  • More loops
  • More current

13
Works other way too!
  • Move the magnet to get an electric current.
    (Section 3)

http//media.web.britannica.com/eb-media /73/63373
-004-CDB7E548.gif
14
Electric motor
  • An alternating current causes a magnet to spin
  • The magnet is attached to some mechanical device
    that spins (ex fan blade)

15
Electric generator
  • A spinning magnet causes an alternating current.

16
Circuits
  • energy source
  • load
  • wires

17
Circuits
  • series
  • lined up like train cars
  • one current path
  • same current everywhere
  • parallel
  • branches
  • more than one current path
  • same voltage on each branch

18
Schematic of a DC circuit with three resistor in
series
http//www.school-for-champions.com/science/dc_cir
cuits.htm
19
Schematic of a DC circuit with three resistor in
parallel
http//www.school-for-champions.com/science/dc_cir
cuits.htm
20
V IR
  • What happens to current if voltage increases?
  • What happens to current if resistance increases?

21
SI units
  • electric potential (aka voltage) volt
    (V)
  • current ampere (A)
  • resistance ohm (O)

22
Decrease resistance in a wire
  • shorter wire
  • thicker wire
  • cool the wire
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