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131 Cards in this Set
- Front
- Back
What is the purpose of a bypass capacitor
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removes AC by providing low impedance path to ground
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describe an inverting op-amp circuit
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input and putput signals are 180 degrees out of phase
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What type capacitor is used in an op-amp active filter circuit
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polystyrene
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What factors determine sensitivity of a receiver
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bandwidth, noise figure
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What's the prime uses of an op-amp RC active filter?
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audio filters for receivers
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What does the accuracy of a frequency counter depend on
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internal crystal reference
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Whats the function of decade counter digital IC
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produce 1 output pulse for every 10 input pulses
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What is a flip-flop circuit
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binary sequential logic element with 2 stable states
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what type of digital IC is also called a latch
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a flip flop
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what is meant by modulation
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mixing process where information is imposed on a carrier
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why are silicon crystals packed in lead foil for shipping
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protect against static discharge
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what is the SWR of a properly connected transmission line
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as near to 1:1 as possible
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what is the DC resistance in a shunt fed 1/4 wave Marconi antenna
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zero
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where does conductance take place in a waveguide
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in the walls of the waveguide
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what are wave guides?
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hollow conductors which carry high frequency current
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how is the resonant frequency of a hertz antenna lowered
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place an inductance in series with antenna
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whats the effect of adding a capacitor in series to a marconi antenna
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increases circuit resonant frequency
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what is the best standing wave ratio
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1:1
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what is meant by antenna bandwidth
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frequency range in which an antenna works well
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what is the frequency range of aircraft HF communications
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2.00 MHz to 29.99 MHz
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what is the main characteristic of a tunnel diode
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a negative resistance region
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what type diode is capable of amplication and oscillation
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tunnel diodes
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what are the two structural categories of semiconductor diodes
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junction and point contact
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what is the main purpose of a zener diode
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constant voltage under conditions of changing current
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what is the voltage range available in zener diodes
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2.4 volts to 200 volts
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why are power losses low in cavity resonators
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conducting surfaces are large
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how is light emiision from an LED modulated
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current passing thru the diode
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how long does it take a radar pulse to travel a mile
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6.17 microseconds
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whats the effect of corrosion on a parabolic antenna dish
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poor performance for weak targets
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a gunn diode oscillator takes advantage of what effect
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negative resistance and bulk effect
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what is the main characteristic of a varactor diode
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internal capacitance varies with applied voltage
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what is meant by back EMF
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voltage that opposes the applied EMF
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what is the time constant of an RC circuit
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time required to charge the capacitor to 63.2% of supply voltage
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what is the piezoelectric effect
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mechancial vibration of a crystal by voltage
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what are the three general groupings of filters
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high pass, low pass, band pass
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how many gates does a medium scale integrated circuit have
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10-99 gates
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what does slew rate of an op-amp mean
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output voltage change per microsecond
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what fluid makes up liquid crystals in LCD displays
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nematic fluid
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how many JK flip-flops are needed for a MOD-16 ripple counter
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4
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how many RS flip-flops are needed for an 8 bit storage register
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8
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what is the main benefit of a Schottky diode
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no negative resistance region
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what determines the color radiated by an LED
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material used to construct the device
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whats the main advantage to LEDs
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low power consumption and long life
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what bias exists when a transistor operates in saturation
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base emitter and collector base junctions are both forward bias
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what is an enhancement mode FET
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a FET without a channel
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what are the operating modes for field-effect transistors
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depletion and enhancement mode
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what is the impedance of a reverse biased diode junction
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high impedance to electron flow
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what type diode contains no minority carriers in the junction
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hot-carrier diodes
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what logic states do TTL device inputs assume if left open
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a high logic state
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what is the best supply voltage for TTL integrated circuits
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5.0 volts
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what are the major advantages of CMOS over other devices
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low current consumption
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whats the input impedance of a theoretically ideal op-amp
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infinite
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what determines gain of a closed loop op-amp circuit
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external feedback network
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what are the three terminals of a field effect transistor
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gate, drain, source
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what are the two types of junction field-effect transistors
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n-channel
p-channel |
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what precautions are needed in handling CMOS devices
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prevention of damage from static charges
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what doe the initials CMOS stand for
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complementary metal oxide semiconductor
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what determines bandwidth and response in a crystal lattice filter
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frequencies of individual crystals
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describe a crystal lattice filter
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narrow bandwidth, steep skits, made of quartz crystals
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whats one advantage of ASCII code instead of Baudot code
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you can transmit upper and lower case text
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in pulse width modulation, what parameter does the modulating signal very
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pulse duration
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what is the peak to peak voltage at a common household outlet
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331 volts
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what is the RMs voltage at a common household power outlet
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117vac
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how can you best determine RMS voltage of a complex waveform
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measure the head effect in a known resistor
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whats the the peak voltage of a common household outlet
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165.5 volts
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describe a sawtooth wave
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straight line rise time faster than fall time
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what is the period of a wave
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time required to complete one cycle
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how many degrees are in one complete sine wave cycle
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360 degrees
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whats the purpose of a coupling capacitor
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blocks direct current, passes alternating current
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what occurs if the load is removed from a series DC motor
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it will accelerate until it flies apart
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why do we tin component leads
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decreases heating time
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what tool measures the condition of lead acid batteries
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hydrometer
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what are the best insulations at UHF frequencies
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teflon and mica
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whats the purpose of flux
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removes and prevents oxide formation
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whats the best way to remove insulation from wire
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thermal stripper
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how is solder removed from holes in a printed boards
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soldering iron and a suction device
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3:00 pm US central standard time equals what UTC time (during winter)
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2100
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what solder type is most used when hand soldering electronics
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60% tin/40% lead
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one nautical mile equals how many statute miles
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1.15 statute miles
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what is wetting during a soldering operation
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blending of solder and copper to form a new alloy
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what is the frequency range of UHF
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.3-3 GHz
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what frequency band includes 30-300 MhZ
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VHF
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what determines the magnetic field strength around a conductor
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amount of current
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what factors determine the capacitance of a capacitor
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area of plates: distance between plates; dielectric constant between plates
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what device stores electrical energy in an electrostatic field
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a capacitor
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what is a magnetic field
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a force set up when current flows thru a conductor
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where does most RF current flow in a conductor
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along its surface
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what does the vertical axis of a spectrum analyzer display
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amplitude
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what factors limit the accuracy of a frequency counter
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time base, speed of logic, stability
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whats the wavelength of a signal at 500 MHz
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60 centimeters
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how long does it take a radar signal to travel 1 nautical mile
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6.2 microseconds
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what colors are available in LEDs
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red green orange yellow
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what bias is required for an LED to produce luminescence
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forward bias
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what is normal operating current and voltage of a LED
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1.7 volts 20 mA
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what are the three terminals of a TRIAC
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gate, anode one, anode two
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what are the two stable conditions of an SCR
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conducting and non conducting
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why are silicon and germanium used in semiconductor devices
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they exhibit both metallic and non-metallic properties
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what are the three terminals of an SCR
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anode, cathode, gate
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what are the elements of a unijunction transistor
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base one, base two, emitter
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what does it mean for a transistor to be cut off
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no current between emitter and collector
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What does it mean for a transistor to be fully saturated
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the collector current is at its maximum value
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what is the transitiion region with regard to a transistor
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area of low charge density around a P-N junction
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what is the beta with regard to bipolar transistors
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change of collector current relative to base current
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what is the alpha with regard to bipolar transistors
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change of collector current relative to emitter current
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why type diode is used in RF switches and phase shifting devicess
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PIN diodes
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what are the three terminals of bipolar transistor
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base, collector, emitter
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what diode is made of metal whisker touching a semiconductor die
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point contact diode
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what is the common use of point contact diodes
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as an RF detector
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how are junction diodes rated
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max forward current and peak inverse voltage
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what limits forward current in a junction diode
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the junction temperature
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what is the common use of a hot-carrier diode
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VHF and UHF mixers and detectors
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how much energy does a receiver consume drawing 50 watts for 10 hours
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1,800,000 joules
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how much voltage may be connected across a 20 watt 2000 ohm resistor
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200 volts
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what is the resistance of a 60 watt 117 volt lamp
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228 ohms
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whats the purpose of a shunt resistor on an ammeter
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increase ampere indicating range
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What's the purpose of a multiplier resistor on a voltmeter
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increase voltage indicating range
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what's the voltage of a fully charged lead-acid cell
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2.06 volts
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whats the voltage of a fully charged edison storage cell
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1.2 volts
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the ratio of magnetic flux density to magnetizing force is what concept
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permeability
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if voltage is doubled and resistance tripled, whats the final current
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2/3rds the original current
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how many watts equals one horsepower
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746 watts
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how does the value of an RF current relate to its heating value
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they are the same
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volts x amps x power factor=what?
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true power
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number of turns times current in amps= what unit of measure?
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gilbert
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in what condition will gas be a good conductor
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when ionized
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how will halving a conductor cross section affect resistance
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resistance will double
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what must a transformer have to step up its input voltage
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more wire turns on its secondary than its primary
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how is output voltage of a separately excited AC generator controlled
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by varying the field current
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whats the total voltage when 12 NiCad batteries connect in series?
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15 volts
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why is a crowbar circuit often added to a power supply
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protects load by activating circuit protection devices
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what is the operating voltage of a nickel-cadmium cell
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approximately 1.25 volts
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