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Physics Chapter 3 and 4
Electricity and Electromagnetism
50
Physics
09/23/2015

Term
 Hans Oersted
Definition
 discovered that electric currents make magnetic fields, placed a magnetic compass in close proximity to an electric current
Term
Definition
 Turned mechanical energy into electrical energy which is the basis for the generator. Used magnetic fields to make a current.
Term
 5 laws of electrostatics
Definition
 Repulsion, inverse square law, distribution, concentration, movement
Term
 Repulsion
Definition
 attraction - like charges repel, unlike charges attract
Term
 Inverse square law
Definition
 force between 2 objects is inversely proportional to the square of the distance between them
Term
 Distribution
Definition
 Charges reside on the external surfaces of conductors and equally throughout nonconductors
Term
 Concentration
Definition
 The greatest concentration of charge will be on the surface where curvature is sharpest.
Term
 Movement
Definition
 Only negative charges move along solid conductors because the electrons outside the nucleus are easily moved along.
Term
 Ohm's Law
Definition
 The current along a conductor is proportional to the potential difference (force). V=IR
Term
 Lines of Force
Definition
 Lines of Force always flow from N to S outside a magnet and S to N inside a magnet
Term
 orbital magnetic moment
Definition
 The motion of a charged particle creates a magnetic force field perpendicular to the motion.
Term
 shell-type transformer
Definition
 the most common type in use today
Term
 solenoids and electromagnets
Definition
 The strength of __________________ is determined by the number of loops (or turns) of wire, the current strength, and the permeability of the core.
Term
 Why does induction require AC current?
Definition
 A coil supplied with alternating current permits a steady flow of electrons and establishes an electromagnetic effect for half the cycle. However, at the instant the current supply reverses, the previously established electromagnetic north and south 6970 poles will induce an opposing potential difference, thus attempting to induce against the incoming supply of electrons.
Term
 Electrical circuit
Definition
 An electrical circuit is a pathway (commonly copper wire) that permits electrons to move in a complete circle from their source, through resisting electrical devices and back to the source.
Term
 Rectification
Definition
 is the process by which alternating current is changed to pulsating direct current, and requires the use of one-way electrical devices called rectifiers. Needed for x-rays because if a flow of electrons occurs in the wrong direction the tube may be damaged beyond repair.
Term
 Permeability
Definition
 is the ease with which a material can be magnetized
Term
 Retentivity
Definition
 is the ability of a material to stay magnetized.
Term
 Step-down transformer
Definition
 decreases voltage from primary to secondary while increasing amperage.
Term
 Semiconductor
Definition
 A material that allows electrons to flow freely under certain conditions (conductor) or that inhibits electron flow under certain conditions (insulator).
Term
 Induction
Definition
 The process of electrical fields acting on one another without contact.
Term
 Volts
Definition
 The unit of potential difference.
Term
 Insulators
Definition
 have very poor or nonexistent conduction bands. The best insulators are materials with complex molecular structures, such as wood, plastic, glass, and rubber.
Term
 Series and parallel circuit
Definition
 When a single series-wired light burns out, it breaks the circuit and all the lights go out. When a single parallel-wired light burns out, it breaks the circuit in its parallel branch only and the other lights continue to operate. The classic example of the difference is illustrated by comparing strings of Christmas lights in series versus parallel circuits.
Term
 Transformer
Definition
 A device in which two coils are placed near one another without electrical connection. The number of turns in the coils differs, causing a change in current in the secondary coil; this serves to either increase or decrease the voltage.
Term
 Electromagnet
Definition
 Temporary magnet produced by moving electric current.
Term
 Electromagnification
Definition
 Describes the process of electron charges being added to or subtracted from an object.
Term
 Capacitor
Definition
 A device capable of accumulating and storing an electrical charge.
Term
 Lines of flux
Definition
 The force fields that are created when magnetic dipoles orient to create a magnet; also called lines of force and magnetic field.
Term
 Electrification
Definition
 Describes the process of electron charges being added to or subtracted from an object.
Term
 Friction
Definition
 Electrification that occurs when one object is rubbed against another and, due to differences in the number of electrons available on each, electrons travel from one to the other.
Term
 Contact
Definition
 Electrification by contact occurs when two objects touch, permitting electrons to move from one to the other.
Term
 Induction
Definition
 The process of electrical fields acting on one another without contact.
Term
 Vacuum
Definition
 The process of electrical fields acting on one another without contact.
Term
 Semiconductor
Definition
 A material that allows electrons to flow freely under certain conditions (conductor) or that inhibits electron flow under certain conditions (insulator).
Term
 Current flow
Definition
 Electrons will move from highest to lowest concentration
Term
 Current
Definition
 The quantity or the number of electrons flowing at any given time. Measured in amperes.
Term
 Force/Strength/Potential differences
Definition
 is the difference in number of electrons in excess at one end of the circuit and deficiency at the other end (high concentration to low). Is measured in volts.
Term
 Resistance and length of conductor are ____________
Definition
 directly proportional
Term
 Resistance and diameter of the conductor are _____________
Definition
 inversely proportional
Term
 Heat varies in relationship with ___________
Definition
 resistance
Term
 Natural magnets
Definition
 Created when iron oxide remains in the earthâ€™s magnetic field for ages, slowly orienting the magnetic dipoles in the same direction (e.g., lodestones).
Term
 Artificial permanent magnet
Definition
 Manufactured from steel alloy called alnico, composed of aluminum, nickel, and cobalt.
Term
 Electromagnet
Definition
 Temporary magnet produced by moving electric current.
Term
 Magnetic Pole
Definition
 Every magnet has a north and a south no matter how many times it has been divided.
Term
 Mutual induction
Definition
 The result of two coils being placed in close proximity with a varying current supplied to the first coil, which then induces a similar flow in the second coil.
Term
 Generator
Definition
 A device that converts mechanical energy to electrical energy using moving lines of flux in relationship to a conductor to induce current; also known as a dynamo.
Term
 Motor
Definition
 A device that is supplied with electrical current to produce mechanical motion.
Term
 Half-wave rectification
Definition
 Suppressed rectification resulting from only half of the incoming alternating current being converted to pulsating direct current; called self-rectification.
Term
 Full-wave rectification
Definition
 The conversion of the opposing half of the incoming electron flow to always move in the same direction, instead of discarding half the cycle.*All modern x-ray equipment uses full-wave rectification, which results in twice the output.
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