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20 Cards in this Set
- Front
- Back
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General Properties of Magnets (3)
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-Have polarity
-Poles come in pairs -Can polarize nonpolar materials |
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Magnetic Flux
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Number of magnetic field lines passing through a surface (strength)
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Describe the flow of field lines.
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It comes out of the north and goes back into the south.
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Right Hand Rule #1
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Given: CURRENT
Find: DIRECTION OF MAGNETIC FIELD -Point thumb to the direction of current flow -Follow your fingertips- that is the direction of the MAGNETIC FIELD. |
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Right Hand Rule #2
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Given: MAGNETIC FIELD
Find: NORTH POLE -Curl fingers with fingertips pointing to the direction of magnetic field -The thumb points to the north pole |
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How to increase the strength of an electromagnet
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-Increase # of loops
-Increase current -Place an iron rod inside coil |
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Relationship between Magnetic Field and Force
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A magnetic field exerts no force on electric charge, but it does on a moving charge, or CURRENT
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Right Hand Rule #3
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Given: MAGNETIC FIELD & CURRENT
Find: DIRECTION OF FORCE -Point FINGERS in direction of MAGNETIC FIELD -Point THUMB in direction of CURRENT FLOW -PALM then faces the direction of the FORCES acting on the wire. |
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Relationship between two wires with opposite current flows
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If current flows in opposite directions in two wires, the wires will repel one another.
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Faraday's discovery
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Electric current can be induced from motion of a wire in a magnetic field.
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Electromotive Force (EMF)
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-Potential increase
-Depends on MAGNETIC STRENGTH, VELOCITY of wire perpendicular to field, and LENGTH of wire. |
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Electric Generators
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Converts mechanical energy to electrical energy.
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How electric generators work
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It consists of a number of wire loops placed in a strongmagnetic field.
Each side of the coil moves alternately up and down through the field, and the current alternates direction in the loops. Thus, the generator develops alternating voltage and current. |
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Difference between a generator and a motor
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-Similar, but they have opposite energy conversion.
-Motor- Electric:Mechanic -Generator- Mechanic:Electric |
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How EMF is induced
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Current or wire moving through electric field produces voltage difference.
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Lenz's Law
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The direction of the induced current is such that the magnetic field resulting from the induced current opposes the change in the field that caused the induced current.
(Direction of current oppose that of magnetic field) |
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Induce
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Creation of electric or magnetic forces
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Transformer
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Device used to increase or decrease AC voltage.
AC current through the primary coil induces an alternating EMF in the secondary coil. Then the voltages in alternating current circuits may be increase or decreased by transformers. |
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Mutual Inductance
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In process which in the changing current in the primary coil varies the magnetic field, and the varied magnetic field induces a varying EMF.
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Step Up/Down Transformer
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UP: 2nd V > 1st V
DOWN: 2nd V < 1st V |
