Hans Oersted
discovered that electric currents make magnetic fields, placed a magnetic compass in close proximity to an electric current
Michael Faraday
Turned mechanical energy into electrical energy which is the basis for the generator. Used magnetic fields to make a current.
5 laws of electrostatics
Repulsion, inverse square law, distribution, concentration, movement
Repulsion
attraction - like charges repel, unlike charges attract
Inverse square law
force between 2 objects is inversely proportional to the square of the distance between them
Distribution
Charges reside on the external surfaces of conductors and equally throughout nonconductors
Concentration
The greatest concentration of charge will be on the surface where curvature is sharpest.
Movement
Only negative charges move along solid conductors because the electrons outside the nucleus are easily moved along.
Ohm's Law
The current along a conductor is proportional to the potential difference (force). V=IR
Lines of Force
Lines of Force always flow from N to S outside a magnet and S to N inside a magnet
orbital magnetic moment
The motion of a charged particle creates a magnetic force field perpendicular to the motion.
shell-type transformer
the most common type in use today
solenoids and electromagnets
The strength of __________________ is determined by the number of loops (or turns) of wire, the current strength, and the permeability of the core.
Why does induction require AC current?
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.
Electrical circuit
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.
Rectification
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.
Permeability
is the ease with which a material can be magnetized
Retentivity
is the ability of a material to stay magnetized.
Step-down transformer
decreases voltage from primary to secondary while increasing amperage.
Semiconductor
A material that allows electrons to flow freely under certain conditions (conductor) or that inhibits electron flow under certain conditions (insulator).
Induction
The process of electrical fields acting on one another without contact.
Volts
The unit of potential difference.
Insulators
have very poor or nonexistent conduction bands. The best insulators are materials with complex molecular structures, such as wood, plastic, glass, and rubber.
Series and parallel circuit
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.
Transformer
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.
Electromagnet
Temporary magnet produced by moving electric current.
Electromagnification
Describes the process of electron charges being added to or subtracted from an object.
Capacitor
A device capable of accumulating and storing an electrical charge.
Lines of flux
The force fields that are created when magnetic dipoles orient to create a magnet; also called lines of force and magnetic field.
Electrification
Describes the process of electron charges being added to or subtracted from an object.
Friction
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.
Contact
Electrification by contact occurs when two objects touch, permitting electrons to move from one to the other.
Induction
The process of electrical fields acting on one another without contact.
Vacuum
The process of electrical fields acting on one another without contact.
Semiconductor
A material that allows electrons to flow freely under certain conditions (conductor) or that inhibits electron flow under certain conditions (insulator).
Current flow
Electrons will move from highest to lowest concentration
Current
The quantity or the number of electrons flowing at any given time. Measured in amperes.
Force/Strength/Potential differences
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.
Resistance and length of conductor are ____________
directly proportional
Resistance and diameter of the conductor are _____________
inversely proportional
Heat varies in relationship with ___________
resistance
Natural magnets
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).
Artificial permanent magnet
Manufactured from steel alloy called alnico, composed of aluminum, nickel, and cobalt.
Electromagnet
Temporary magnet produced by moving electric current.
Magnetic Pole
Every magnet has a north and a south no matter how many times it has been divided.
Mutual induction
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.
Generator
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.
Motor
A device that is supplied with electrical current to produce mechanical motion.
Half-wave rectification
Suppressed rectification resulting from only half of the incoming alternating current being converted to pulsating direct current; called self-rectification.
Full-wave rectification
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.
