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Electricity and Magnetism CRCT review
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just like gravity A force that depends on: Size (mass or charge of objects) Distance between the centers
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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?
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static electricity Electric charges are separated. More of either protons or electrons in one place. How? Move electrons
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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
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Electric current What is electric current? What does an electric current cause? What is caused when the current is changing?
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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.
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magnetic properties Always has both north and south pole Cut in half = two whole magnets
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Earth’s magnetic poles http://hyperphysics.phy-astr.gsu.edu/ hbase/magnetic/imgmag/mearthbar.gif
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solenoid Coil of wire
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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
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Stronger electromagnet More loops More current
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Works other way too! Move the magnet to get an electric current. (Section 3) http://media.web.britannica.com/eb-media http://media.web.britannica.com/eb-media /73/63373-004-CDB7E548.gif
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Electric motor An alternating current causes a magnet to spin The magnet is attached to some mechanical device that spins (ex: fan blade)
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Electric generator A spinning magnet causes an alternating current.
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Circuits energy source load wires
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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
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Schematic of a DC circuit with three resistor in series http:// www.school-for-champions.com/science/dc_circuits.htm
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Schematic of a DC circuit with three resistor in parallel http:// www.school-for-champions.com/science/dc_circuits.htm
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V = IR What happens to current if voltage increases? What happens to current if resistance increases?
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SI units electric potential (aka: voltage) = volt (V) current = ampere (A) resistance = ohm (Ω)
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Decrease resistance in a wire shorter wire thicker wire cool the wire
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