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Bushong Ch 5

The study of stationary electric charges is called? Electrostatics
Electrification can be created by? Contact, friction or conduction
The primary function of an x-ray imaging system is to? Convert electric energy into electromagnetic energy.
Examples of energy conversion automobile battery from chemical to electric, an electric motor converts electric energy to mechanical energy.
Matter has mass and energy equivalence. Matter also may have? Electric charge.
Electric charges associated with an electron and a proton have the same ???? but opposite ??? magnitude, signs.
An object that has too few or too many electrons is said to be? Electrified
An electron charge is too small to be useful, so the fundamental unit of electric charge is? The coulomb (C)
The smallest unit of electric charge is? an electron
How many electrostatic laws are there? 4
What are the electrostatic laws? 1. Unlike charges attract, like charges repel. 2. Coulomb's law. 3. Electric charge distribution is uniform throughout or on the surface. 4. Electric charge of a conductor is concentrated along the sharpest curvature of the surface.
The unit of electric potential is? the volt (V)
The study of electric charges in motion is called? Electrodynamics
Any substance through which eletrons flow is? A conductor
What are some examples of electrical conductors? copper is one of the best, water is good because of the salts and other impurities, most metals are good.
What is an insulator? any material that does not allow electron flow.
What are some examples of insulators? Glass, clay and other earthlike materials
What do the insulators do? They confine electron flow to the conductor.
What is a semiconductor? A material that under some conditions behaves as an insulator and in other conditions behaves as a conductor.
Who first demonstrated semiconduction? When? William Shockley, 1946.
Examples of semiconductor materials? silicon (Si), germanium (Ge).
What did the development of semiconduction lead to? microchips and the explosive rise of computer technology.
The ability of the property of some materials to exhibit no resistance below a critical temperature is called? Superconductivity
At room temperature, all material resists the flow of electricity. Resistance (increases or decreases) as the temperature of material is (increase or reduced)? decreases; reduced
Name two superconducting materials that allow electrons to flow without resistance. Niobium and titanium
What are the characteristics of superconductor niobium? no resistance to electron flow
What are the characteristics of superconductor titanium? no resistance to electron flow
What are the characteristics of conductor copper? Variable resistance
What are the characteristics of conductor aluminum? Obeys Ohm's law. Requires a voltage.
What are the characteristics of Semiconductor Silicon? Can be conductive
What are the characteristics of Semiconductor Germanium? Can be resistive. Basis for computers
What are the characteristics of Insulator rubber? Does not permit electron flow.
What are the characteristics of Insulator glass? Extremely high resistance. Necessary with high voltage.
What is an electric current? When resistance is controlled and the conductor is made into a closed path.
True or False. Increasing electric resistance results in a reduced electric current. True.
What is electric current measured in? amperes(A)
The ampere is proportional to? The number of electrons flowing in the electric circuit.
One ampere is equal to? An electric charge of 1C flowing through a conductor each second.
The manner in which electric currents behave in an electric circuit is described by a relationship known as? Ohm's Law V=IR where V is electric potential in voltage, I is electric current in amperes, and R is electric resistance in ohms.
Ohm's law states? The voltage across the total circuit or any portion of the circuit is equal to the current times the resistance.
Usually electric circuits can be reduced to two basic types, name them. Series circuits and parallel circuits.
What is a series circuit? All circuit elements are connected in a line along the same conductor. Like the old christmas lights.
What is a parallel circuit? Contains elements that are connected at their ends rather than lying in a line along a conductor.
Electrons that flow in only one direction constitute? DC
Electrons that flow alternately in opposite directions constitutes? AC
An x-ray imaging system requires ???? of electric power? 20 to 150 kW
Any charged particle in motion creates? magnetic field
The lines of a magnetic field are always? closed loops
What is the formula for electric power? P=IV, where P is the power in watts, I is the current in amperes and V is the electric potential in volts.
Any charged particle in motion creates? A magnetic field.
Alternating current is represented graphically by? A sinusoidal electric wavefom
What is electron spin? The rotation of electrons on an axis either clockwise or counter clockwise. The electron spin creates a magnetic field.
What is a bipolar or dipolar field? It always has a north and a south pole.
What is a magnetic domain? An accumulation of many atomic magnets with their dipoles aligned.
Is the magnetic field of a charged particle, such as an electron in motion, perpendicular or parallel to that particle in motion? perpendicular
There are how many principle types of magnets? What are they? There are three principle types of magnets. Natural magnets, artificially induced permanent magnets, and electromagnets.
The best example of a natural magnet is? The earth
Magnetic permeability is the ability of a material to attract???? ???? The lines of magnetic field intensity
What is an example of an artificially produced permanent magnets? a compass
All matter can be classified according to the manner in which it interacts with? an external magnetic field.
Electromagnets consist of wire wrapped around an iron core. When an electric current is conducted throught the wire, what is created? a magnetic field.
What are the four magnetic states of matter? Nonmagnetic, diamagnetic, paramagnetic, and ferromagnetic.
Materials that are unaffected when brought into a magnetic field are called? Nonmagnetic, such as wood and glass.
Materials that are weakly repelled by either magnetic poles are called? Diamagnetic, such as water and plastic
Materials that are strongly attracted by a magnet are called? Ferromagnetic, such as iron, cobalt and nickel.
Materials that lie somewhere between ferromagnetic and nonmagnetic is called? Paramagnetic, such as gadolinium. Contrast agents employed in MRI are also paramagnetic.
The degree to which a material can be magnetized is? It's magnetic susceptibility.
A coil of wire is called? a solenoid
Faradays law states that the magnitude of the induced current depends on four factors which are: The strength of the magnetic field, the velocity of the magnetic fiels, the angle of the conductor to the magnetic field, and the number of turns in the conductor.
What powers the rotating anode of the x-ray tube? An induction motor.
Another device that uses the interacting magnetic fields produced by changing electric currents is the? Transformer
A transformer changes the intensity of alternating??? voltage and current
How many types of transformers are there? Three
What are the different types of transformers? Autotransformers, Shell-type transformers, and closed-core transformers.
What is the transformer used for? To change the magnitude of voltage and current in an AC circuit.
What is the transformer law? The law states that the change in voltage is directly proportional to the ratio of the number of turns (windings) of the secondary coil to the number of turns in the primary coil.
What is the mathematical formula for the transformer law? Vs/Vp = Ns/Np Secondary Voltage/Primary Voltage = Number of turns of the secondary coil/number of turns of the primary coil
A transformer with a turn ratio greater than 1 is? A step up transformer
A transformer with a turn ratio less that 1 is? A step own transformer
The type of transformer that is built about a square core of ferromagnetic material built up of laminated layers of iron; it helps reduce energy losses caused by eddy currents is called? A closed core transformer
A transformer that has one winding and varies both voltage and current by self-induction is called? An auto transformer. (used in x-ray imaging systems)
A type of transformer that confines more of the magnet field lines of the primary winding because there are essentially two closed cores is called? Shell type transformers
Created by: Baker RAD 2012 on 2012-02-13

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