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Physics Chapter 3 and 4
Electricity and Electromagnetism
50
Physics
Undergraduate 2
09/23/2015

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Term
Hans Oersted
Definition
discovered that electric currents make magnetic fields, placed a magnetic compass in close proximity to an electric current
Term
Michael Faraday
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 earth’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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