Chapter 4 Flashcards
Electrostatics
is the science of stationary electric charges.
Electrodynamics
The science of electric charges in motion
Electromagnetism
Describes how electrons are given electric potential energy (voltage) and how electrons in motion creates magnetism
is a means of transfer- ring electric potential energy from one position to another, as in a transformer
Electromagnetic induction
The primary function of an x-ray imaging system
is to convert electric energy into electro- magnetic energy.
Electric ground
Earth
the fun- damental unit of electric charge is the
1 C = 6.3 × 10^18 electron charges.
The force of attraction between unlike charges or repulsion between like charges is attributable to the electric field.
electrostatic force.
any substance through which electrons flow easily
conductor
any material that does not allow electron flow
insulator
material that under some conditions behaves as an insulator and in other conditions behaves as a conductor.
semiconductor
He demonstrated semiconduction in 1946
William Shockley
The principal semiconductor materials are
silicon (Si) and germanium (Ge).
is the property of some materials to exhibit no resistance below a critical temperature (Tc).
Superconductivity
Superconductivity was discovered in ___ but was not developed commercially until the early ____
1911 ~ 1960s
Material of superconductor
Niobium
Titanium
Material of conductor
Copper
Aluminum
Material of semi conductor
Silicon
Germanium
Material of insulator
Rubber
Glass
all circuit elements are connected in a line along the same conductor.
series circuit,
RULES FOR SERIES CIRCUITS
The total resistance is equal to the sum of the individual resistances.
The current through each circuit element is the same and is equal to the total circuit current.
The sum of the voltages across each circuit element is equal to the total circuit voltage.
Inhibits flow of electrons
Resistor
Provides electric potential.
Battery
Momentarily stores electric charge
Capacitor
Increases or decreases voltage by fixed amount (AC only)
Transformer
Allows electrons to flow in only one direction
Diode
contains elements that are connected at their ends rather than lying in a line along a conductor.
parallel circuit
RULES FOR A PARALLEL CIRCUIT
The sum of the currents through each circuit element is equal to the total circuit current.
The voltage across each circuit element is the same and is equal to the total circuit voltage.
The total resistance is the inverse of the sum of the reciprocals of each individual resistance.
is the flow of electrons through a conductor.
Electric current, or electricity,
Current in which electrons oscillate back and forth/electrons that flow alternately in opposite directions
alternating current (AC).
These electrons can be made to flow in one direction along the conductor
direct current (DC).
Electric power is measured in
watts (W).
Common household electric appliances, such as toasters, blenders, mixers, and radios, generally require
500 to 1500 W of electric power.
Light bulbs require
30 to 150 W of electric power.
An x-ray imaging system requires
20 to 150 kW of electric power.
The small magnet created by the electron orbit is called
magnetic dipole.
An accumulation of many atomic magnets with their dipoles aligned creates a
magnetic domain.
is the ability of a material to attract the lines of magnetic field intensity.
Magnetic permeability
are weakly repelled by either magnetic pole.
Diamagnetic materials
These are strongly attracted by a magnet and usually can be permanently magnetized by exposure to a magnetic field.
Ferromagnetic
is one of the more useful magnets produced from ferromagnetic material, includes alloy, aluminum, nickel and cobalt.
alnico
lie somewhere between ferromagnetic and nonmagnetic. They are very slightly attracted to a magnet and are loosely influenced by an external magnetic field.
Paramagnetic materials
magnetic susceptibility.
The degree to which a material can be magnetized
Unaffected by a magnetic field, wood/glass
Nonmagnetic
Weakly repelled from both poles of a magnetic field, water & plastic
Diamagnetic
Weakly attracted to both poles of a magnetic field, gadolinium
Paramagnetic
Can be strongly magnetized, Iron, nickel, cobalt
Ferromagnetic
can be made into magnets by induction.
Ferromagnetic
The SI unit of magnet field strength is
tesla
One tesla (T) =
10,000 gauss (G).
solenoid
A coil of wire
is a current-carrying coil of wire wrapped around an iron core, which intensifies the induced magnetic field.
An electromagnet
His experiment demonstrated that electricity can be used to generate magnetic fields.
Hans Oersted
concluded that an electric current cannot be induced in a circuit merely by the presence of a magnetic field.
He observed the current in a changing magnetic field
Michael Faraday
It powers the rotating anode of an x-ray tube.
An induction motor
changes the intensity of alternating voltage and current
transformer
has one winding and varies both voltage and current.
autotransformer
The type of transformer discussed thus far, built around a square core of ferromagnetic material, is called a
closed-core transformer
This type of transformer confines even more of the magnet field lines of the primary winding because the secondary is wrapped around it and there are essentially two closed cores. This type is more efficient than the closed-core transformer. Most currently used transformers are this
shell-type transformer
Four states of matter
Conductor, insulator, semiconductor superconductor
Work with electric current
Electrical Engineer
Concerned with electron flow
Physicist
The lines of force exerted on charged ions in the tissues by electrodes
Electric field
Measures electric voltage
Ammeter
Measures electric potential
Voltmeter
Variable resistor
Rheostat
Variable resistor
Rheostat
A nuclear magnetic dipole created when magnetic field is created by spinning electric charge
* the basis of MRI
Magnetic moment
The small magnet created by the election orbit
Magnetic dipole
An accumulation of many atomic magnets with their dipoles aligned
Magnetic domain
A magnet that gets its magnetism from the earth
Natural magnet
A magnet whose magnetism is induced artificially
Permanent magnet
A coil or wire wrapped around an iron core that intensifies the magnetic field
Electromagnet
A condition where in some materials that are very susceptible are also reluctant to lose their magnetism
Hysteresis
An excellent temporary magnet
Soft iron
An excellent temporary magnet
Soft iron
The force of attraction between unlike poles or repulsion between like poles
Magnetic force
It determines the direction of the magnetic field
Right hand rule
A current carrying coil of wire wrapped around an iron core
Electromagnet
A square core of ferromagnetic material built up of laminated layers of iron
Closed core transformer
A current that opposes the magnetic field that induced it creating a loss of transformer efficiency
Eddy current