Electricity and Magnetism CRCT review. just like gravity A force that depends on: Size (mass or...
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Transcript of Electricity and Magnetism CRCT review. just like gravity A force that depends on: Size (mass or...
just like gravityA force that depends on:
• Size (mass or charge of objects)
• Distance between the centers
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?
static electricity• Electric charges are
separated. More of either protons or electrons in one place.
• How? Move electrons
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
Electric current• What is electric current?
• What does an electric current cause?
• What is caused when the current is changing?
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.
electromagnet• solenoid wrapped around an iron core
• The magnetic field inside iron magnifies the solenoid’s field
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/imgmag/sol3.gif
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
Electric motor• An alternating current
causes a magnet to spin
• The magnet is attached to some mechanical device that spins (ex: fan blade)
Circuitsseries
• lined up like train cars
• one current path
• same current everywhere
parallel
• branches
• more than one current path
• same voltage on each branch
Schematic of a DC circuit with three resistor in series
http://www.school-for-champions.com/science/dc_circuits.htm
Schematic of a DC circuit with three resistor in parallel
http://www.school-for-champions.com/science/dc_circuits.htm
V = IR• What happens to current if
voltage increases?
• What happens to current if resistance increases?
SI units• electric potential (aka: voltage)
= volt (V)
• current = ampere (A)
• resistance = ohm (Ω)