# Shared Flashcard Set

## Details

Unit 1 Parts 1-4
99
Physics
09/19/2011

Term
 Units of charge for electrostatics
Definition
 Coulomb (C)
Term
 Two kinds of electrical charges in an object
Definition
 Positive and Negative
Term
 Repulsion- Attraction Law
Definition
 Like charges repel and unlike charges attract
Term
 Inverse square law
Definition
 Force between 2 charges is directly proportional to the product of their magnitudes and inversly proportional to the square of distance between them
Term
 Concentration of charges
Definition
 Greatest concentration of charge will be on the surface where the curvature is the sharpest
Term
 Movement of charges
Definition
 (Only negative charges move along soild conductors) Protons tighly bound inside nucleus but electrons are outside nucleus and move easily along conductors
Term
 3 Methods of generating static electric charges
Definition
 Friction Contact Induction
Term
 4 classifications of conductors
Definition
 Superconductors Conductors Insulators/ No conductors Semi-Conductors
Term
 Ex of Conductors
Definition
 Copper and Aluminum
Term
 Ex of superconductors
Definition
 Niobium and Titanium
Term
 Ex of Insulators/ No Conductors
Definition
 Rubber and glass
Term
 Ex of Semi-Conductors
Definition
 Silicon and Germanium
Term
 Symbol for Current
Definition
 I
Term
 Descriptors of current flow
Definition
 Quanity of electrons Force of move current Amount of Opposition (Resistance) Direction of Travel
Term
 Quanity of electrons is contorlled by ? and mesured in ?
Definition
 controlled by mAs Measured in Ampere (amps)
Term
 How is force of move current described? Controlled by?
Definition
 Potenital Difference (EMF)   Controlled by kVp
Term
 How is the amount of opposition (resistance) measured?
Definition
 Ohm's
Term
 Factors affecting Resistance
Definition
 Ability to conduct Length of conducter (directly prop) Cross-sectional diameter (inversely prop) Temp (directly prop)
Term
 Series Circut
Definition
 Suppiles less total current Supplies greater total voltage Suppiles greater total resistance
Term
 Parallel Circuit
Definition
 Suppiles greater total current Supplies lower total voltage offers less total resistance
Term
Definition
 when the circuit has more resistance added, the current can short circuit the entire system, which make the wires hot and may cause a fire
Term
 Saftey devices to prevent overload of circuits Which can we change?
Definition
 Circuit breakers and Fuses   Can Change Fuses
Term
 Ohm's Law
Definition
 Voltage: V=IR   Current: I= V                   R Resistnace: R= V                       I
Term
 How is voltage measured?
Definition
 Volts (EMF)
Term
 How is current measured?
Definition
 amperes
Term
 Resistance Vs. Current
Definition
 Higher resistance= less current   Lower resistance = more current   (inveresly prop)
Term
 If you increase resistance it does what to heat?
Definition
 Increases
Term
 Relationship of Power
Definition
 P= VI
Term
 Power loss
Definition
 - in a form of heat   P=I2R
Term
 What does Voltmeter measure?
Definition
 measures potential difference (EMF) (ACV and DVC) between any two points in a circuit
Term
 What does Ammeter measure?
Definition
 Amps current in AC and DC
Term
 What does Ohmmeter measure?
Definition
 Resistance
Term
 If you half the distance to the pt what happens to Mag. Strenght?
Definition
 Increase it 4x
Term
 Magnetic field
Definition
 invisblie force produced by electic charges in motion
Term
 Units of magnetism
Definition
 Telsa (T) and Gauss (G)
Term
 Two Kinds of motion contibute to magnetism
Definition
 Orbital Magnetic MomentSpin Magnetic Moment
Term
 Spin magnetic moment
Definition
 spinning electrions on theier own axis
Term
 Ex of spinning magnetic moment
Definition
 MRI
Term
 Magnetic Domain
Definition
 groups of magnetic atoms with thier dipoles aligned
Term
 3 Princple types of magnets
Definition
 Natural MagnetsArtifical Permanent MagnetsElectromagnets
Term
 Ex of natural magnets
Definition
 Earth, Ore called Lodestones
Term
 Ex. Artifical Permanent magnet
Definition
Term
 Ex. Electromagnets
Definition
 current carrying coil wire wrapped around an iron core
Term
 Electromagenets can only me magnetic if......
Definition
 Current is added (can be turned off)
Term
 More loops of wire prodcudes greater # of magnetic field lines and magnetic field intensity
Definition
 Electromagnets
Term
 What are the two behaviors that are brought into a magnetic field?
Definition
 Magnetic permabilityMagnetic retentiviy
Term
 What is the relationship of magnetic permeability and magnetic retentivity?
Definition
 inversely propEx. Soft iron= high permeability and low retentivity Hard steel= low permeability and high retentivity
Term
 Magnetic permeability
Definition
 easily magnetized
Term
 Magnetic retentivity
Definition
 ability to stay magnetized or resist demagnetization
Term
 Ferromagnetic
Definition
 easily magnetized (Highest)
Term
 Non-magnets
Definition
 cannot be magnetized
Term
 Electricity
Definition
 -Two types of electric charge (+) & (-). –Like charges repel; unlike charges attract.–Electric Force between charges depend on the magnitude of the charges & the distance of magnets between them.–Some materials conduct electric charges; other do not–Electric fields exist around electric charges
Term
 Magnetism
Definition
 –Two types of mag. poles - N & S–Like mag. poles repel; unlike attract.–The mag. force between magnets depends on the strength & the distance between –Some materials can be easily mag. (ferromagnetic) others cannot.–Mag. fields exist around magnets.
Term
 Electromagnetism
Definition
 a current flowing in a conductor (wire) creates a magnetic field around the conductor; Increase current= increase magnetic field
Term
 Solenoid
Definition
 coiling the current carrying conductor (wire) will increase magnetic field strenght in the center of the coil
Term
 Strenght of the current is determined by.....
Definition
 Number of turns or current:increase the current or number of turns in the coil; increase magnetic field stregth in the center of the coil
Term
 Oersted's experiment
Definition
 affect of compass with and without current flow in wire
Term
 Uses of electromagnets
Definition
 remote control devices in circuit breakersDetent button on Rad. Equip.Electromagnet relays on contorol console to protect the RT from Hi-voltage circuit
Term
 What is a Solenoids?
Definition
 a current carrying coil/helix of wire
Term
 Factors affecting effectiveness of solenoids and electromagents
Definition
 diameterlengthcurrent passing along wire
Term
 Strength of solenoids & electromagnets
Definition
 numbers of loops/ turns of wirescurrent strengthpermability of core
Term
 Electromagnetic induction
Definition
 production of current in a conductor by using a changing magnetic field near the conductor
Term
 Require compoents of electromagnetic Induction
Definition
 magnetic fieldconductorrelative motion
Term
 3 ways to induce current in electromagnetic induction
Definition
 1. Move conductor through a stationary unchanging strength mag. field; more practical – generators do this.2. Move mag. field of magnet near a stationary conductor with an unchanging strength mag. field.3. Vary the mag. flux strength from a stationary magnet through a stationary conductor by ↑ or ↓ the current in the wire;
Term
Definition
 1. Strength of mag. field2. Speed of motion between lines of force & conductor3. Angle between mag. field & conductor4. Number of turns / loops in the conducting coil
Term
 the angle between the direction of magnetic field and the conductor
Definition
 — As the angle approaches 90º, the spaces between the lines of force become smaller, progressively more flux lines are cut per sec., larger induced current
Term
 Strength of te magnetic field in electromagnetic induction
Definition
 stronger the magnetic firld the hight the induced voltage
Term
 Flemings right hand thumb rule
Definition
 When the right hand is positioned so the thumb points in direction of conventional current flow, the fingers indicate the direction of the induced magnetic field
Term
 Right hand generator rule
Definition
 When the thumb points in the direction the conductor is moving and the index finger points in the direction of the magnetic lines of force field, the middle finger indicates the direction of conventional current flow. Fleming’s left hand generator rule does the same for actual electron flow.
Term
 Self induction
Definition
 occurs when there is an AC that opens its own flow
Term
 Ex. Self induction
Definition
 autotransformer
Term
 Mutual Induction
Definition
 Two coils=1st coil: primary coil2nd coil: Secondary coil
Term
 Ex. Mutal induction
Definition
 transformer
Term
 Generators are also called.....
Definition
 dynamo
Term
 Generators
Definition
 device that converts mechanical energy of motion (input) to electrical energy (output)
Term
 Parts of a generator
Definition
 armatureelectromagnetset of slip ringsBrushes
Term
 Fleming's Right hand generator rule
Definition
 • Thumb – direction of the conductor• Index Finger – direction of the mag field• Middle Finger – direction of Induced Current
Term
 How is frequency measured?
Definition
 Hertz (Hz)
Term
 Electric motor
Definition
 device that converts electrical to mechanical energy
Term
 What part does a DC motor have?
Definition
 commutator rings
Term
 What parts does a AC motor have?
Definition
 Slip rings and brushes
Term
 Fleming's Left hand motor rule
Definition
 • Index Finger– direction of the mag field• Middle Finger – direction of induced current in conductor• Thumb – direction that Conductor will move
Term
 Ex. of a synchronous motor
Definition
 timing devices (AEC device)
Term
 Synchronous motor
Definition
 AC motor which operates at a fixed synchronous speed prop to the frequency of the appiled AC power
Term
 Synchronous motor must be with the speed of what generator?
Definition
 AC generator
Term
 Induction motor
Definition
 useful with x-ray tube designs with rotating anodes(very powerful Motor)
Term
 Stator located?
Definition
 outside
Term
 rotor located?
Definition
 center
Term
 Single phase Generators
Definition
 solenoid AC100% rippleConversion efficiency 1.00180 degree from positive to negative
Term
 Single phase full wave generators
Definition
 changes the negative half of the cycle to positive
Term
 3-phase generators
Definition
 uses 3 out-of-phase AC cycles sepreated by 120 degrees from each other (1/3 cycle)Ratings up to 2000 mA for 150 kVpExposure time as short as 1 msec.
Term
 3-phase 6-pulse
Definition
 efficiency factor 1.3513.5 % ripple
Term
 3- phase 12-pulse
Definition
 efficiency factor 1.414% ripple-more efficient than single or 3-phase 6 pulse
Term
 High frequency Generators
Definition
 provides nearly a constant voltage potiental less than 1-2 % ripple
Term
Definition
 designed to prodcue exposure in the shortest possible time by operarting the x-ray tube beginning at the highest mA settings and then allowing it to fall during the exposure
Term
Definition
 RT set mAs and kVp
Term