CRAC Bilingual Manual: Circuit Components and Symbols | 电路元件与符号 (77 questions)

The circuit-component symbol in the accompanying figure represents:

1. Aground
2. Bantenna
3. Cresistor
4. Ddiode [F]LK0497.jpg

By manufacturing material, common resistors include: (Choose all that apply.)

1. Acarbon-film resistor
2. Bmetal-film resistor
3. Cwirewound resistor
4. Ddamping resistor

Among components used in assembling an amateur transceiver, the one that is usually marked with a rated dissipation power is:

1. Awirewound resistor
2. Bfilm capacitor
3. Ctransistor
4. Dintegrated circuit

A resistor’s “rated power” means:

1. Athe maximum power the resistor can withstand in normal operation
2. Bthe minimum power needed to keep the resistor operating normally
3. Cthe power the resistor necessarily consumes once connected to a circuit
4. Dthe maximum power the resistor can provide to the circuit

Surface-mount devices (SMDs) are widely used in amateur radio projects. The size codes 0402, 0603, 0805, 1206 etc. refer to:

1. Athe component’s length and width (unit: mm or 0.1 inch)
2. Bcapacitance value (unit: µF)
3. Cresistance value (unit: kΩ)
4. Dinductance value (unit: µH)

A resistor’s color bands are, in order, brown, orange, orange, black. Its resistance is:

1. A13 kΩ
2. B3.7 kΩ
3. C4.7 MΩ
4. D250 Ω

A resistor’s color bands are, in order, yellow, white, red, silver. Its resistance is:

1. A4.9 kΩ
2. B49.2 Ω
3. C4.7 MΩ
4. D390 kΩ

A resistor’s color bands are, in order, silver, black, orange, orange, brown. Its resistance is:

1. A133 Ω
2. B13 kΩ
3. C4.7 MΩ
4. D130 kΩ

A chip resistor is marked “2R7”. Its resistance is:

1. A2.7 Ω
2. B27 Ω
3. C0.27 Ω
4. Da 7 Ω two-resistor network

A chip resistor is marked “3802”. Its resistance is:

1. A38.0 kΩ
2. B208 kΩ
3. C3.8 kΩ
4. D3.802 kΩ

When building circuits with higher operating voltages, one should pay attention to component voltage ratings to improve safety. To ensure the voltage rating of the resistors used, useful experience includes: (Choose all that apply.)

1. Aconsult the manufacturer and select products with a higher rated voltage withstand; or try selecting larger package sizes
2. Bif the selected product cannot meet the design requirement, connect multiple resistors in series
3. Cprefer higher-grade products, e.g., metal-film resistors are better than carbon-film
4. Dwhen the selected product does not meet the design requirement, connect multiple resistors in parallel

A potentiometer is a three-terminal resistive element whose contact end slides on the resistive body. It can be used in a circuit as: (Choose all that apply.)

1. Aan adjustable voltage divider
2. Ba variable resistor
3. Can adjustable transformer
4. Da variable reactance

Which of the following components can be used to implement volume adjustment?

1. Apotentiometer
2. Btransformer
3. Cmodulator
4. Ddemodulator

A capacitor is formed by two electrodes insulated from each other. If subdivided by manufacturing material, common capacitors include: (Choose all that apply.)

1. Aceramic capacitor
2. Belectrolytic capacitor
3. Corganic film capacitor
4. Dinter-winding (stray) capacitance between wires

The monolithic capacitor (独石电容) that we often use is a:

1. Amultilayer ceramic capacitor
2. Bsilver-plated mica capacitor
3. Cwound polyester capacitor
4. Dhigh-frequency ceramic-dielectric capacitor

Among the components used in assembling amateur transceivers, those typically marked with a rated voltage-withstanding (voltage rating) are: (Choose all that apply.)

1. Aelectrolytic capacitor
2. Btantalum capacitor
3. Cfuse
4. Dinductor / coil

When building homemade circuit projects, hobbyists often replace electrolytic capacitors of about 1–100 µF with surface-mount ceramic capacitors of the same capacitance. The advantages of the latter are: (Choose all that apply.)

1. Asmaller size
2. Bbetter frequency characteristics
3. Cnon-polarized
4. Dlower failure rate

In a circuit diagram, if the capacitance value of an electrolytic capacitor is not marked with a unit, the default unit is:

1. Afarad (F)
2. Bmillifarad (mF)
3. Cpicofarad (pF)
4. Dmicrofarad (µF)

In a circuit diagram, if the capacitance of a non-electrolytic capacitor is marked with an integer or decimal greater than 1, the default unit is:

1. Apicofarad (pF)
2. Bmicrofarad (µF)
3. Cfarad (F)
4. Dmillifarad (mF)

If you see a non-electrolytic capacitor’s value marked with a 3-digit code on a circuit diagram or the actual component, it should be read as:

1. Athe first two digits are the base value and the last digit is the number of zeros to append after the base, in picofarads
2. Bthe actual capacitance is the three-digit number multiplied by 1000, in picofarads
3. Cthe actual capacitance is the three-digit number divided by 1000, in farads
4. Dthe first digit is the base, the second is the number of zeros, the third is the tolerance grade, in picofarads

If you see a resistance value marked with a 3-digit code on a circuit diagram or the actual component, it should be read as:

1. Athe first two digits are the base value and the last digit is the number of zeros to append after the base, in ohms
2. Bthe actual resistance is the three-digit number multiplied by 100, in ohms
3. Cthe actual resistance is the three-digit number divided by 100, in ohms
4. Dthe first digit is the base, the second is the number of zeros, the third is the tolerance grade, in kilohms

If you see a resistance marked with 2–3 digits and a letter (e.g., 8R2, 2K7, 1M5) on a diagram or component, it should be read as:

1. Athe letter serves as the decimal point and is read together with the digits as the base value; R, K, or M indicate the unit is ohms, kilohms, or megohms
2. Bconcatenate all the digits and multiply by 100, in ohms
3. Cconcatenate all the digits, then use R/K/M to determine the unit
4. Dthe digits before the letter are the base, those after are the tolerance grade, and R/K/M give the unit

In a circuit diagram, if the capacitance of a non-electrolytic capacitor is marked with a decimal less than 1, the default unit is:

1. Amicrofarad (µF)
2. Bpicofarad (pF)
3. Cfarad (F)
4. Dmillifarad (mF)

In amateur transceivers, the component used to block DC or to provide a bypass for AC signals is:

1. Aa capacitor
2. Ba resistor
3. Can inductor
4. Da diode

When building homemade projects, hobbyists often place a large capacitor in parallel with one or more small capacitors, together serving as an amplifier bypass or a power-supply filter capacitor. The main consideration is:

1. Aat lower frequencies the large capacitor does the main job; as frequency rises the large capacitor’s losses become significant while the small capacitor takes over, extending the circuit’s operating bandwidth
2. Bto prevent the large capacitor from gradually losing capacitance through long-term electrolyte leakage; adding a small one raises the safety margin
3. Cto exploit the rule that parallel capacitors add, obtaining a more precise value for accurate bypass/filtering
4. Dto exploit the rule that parallel capacitors add voltage ratings, raising the circuit’s overvoltage tolerance (especially in mobile use)

Suppose a 1000 µF capacitor is connected across a circuit. Which of the following would NOT seriously disturb the circuit’s operation or create a safety risk?

1. Aacross the output terminals of a 13.8 V DC power supply
2. Bacross the antenna socket of an HF transceiver
3. Cacross an 8 Ω loudspeaker
4. Dacross a 220 V AC mains socket

Which of the following components are made from a coil (wire winding)? (Choose all that apply.)

1. Ainductor
2. Breactor
3. Ccapacitor
4. Dresistor

Inductors come in many types. Those commonly used in RF circuits include: (Choose all that apply.)

1. Aair-core inductor
2. Bmagnetic-core (ferrite/iron-powder) inductor
3. Cdistributed inductance
4. Dparasitic (stray) inductance

The quality factor Q of an inductor is the ratio of its inductance to its loss resistance. Which of the following statements about Q is correct?

1. Atoo low an inductor Q causes power loss and also affects other related circuit characteristics
2. Btoo low an inductor Q affects RF power but does not affect other circuit characteristics
3. Cthe inductor Q is unrelated to the Q of an LC resonant circuit; only the latter is the real Q
4. Donce the inductance is fixed, the Q is also fixed; the two are in direct proportion

A magnetic-core inductor made with a suitable magnetic material has lower loss than an air-core inductor of the same inductance. This is because:

1. Awith a core, a shorter length of wire can achieve the required inductance, reducing the heat loss caused by the wire’s resistance
2. Bthe core dissipates heat more easily than air, thus lowering the inductor’s heat loss
3. Cthe core reflects the originally lost energy back into the wire
4. Dadding a core mitigates the local current-density increase from skin effect, lowering heat loss

Suppose a 100 µH coil is connected across a circuit. Which of the following would NOT seriously disturb the circuit’s operation or create a safety risk?

1. Aacross the antenna socket of an HF transceiver
2. Bacross a 220 V AC mains socket
3. Cacross the output terminals of a 13.8 V DC power supply
4. Dacross an 8 Ω loudspeaker

Xiao Ming used a 4.2 V low-voltage battery and several passive components for a circuit experiment. While connecting the circuit he felt a shock from an unexpectedly high voltage. If the components were as listed, which could have produced the high voltage? (Choose all that apply.)

1. Aa power-transformer winding
2. Ba relay armature coil
3. Ca large electrolytic capacitor
4. Da silicon-carbide high-voltage diode

A switch is an electronic part that controls a circuit using on/off states. The following can be used as switches: (Choose all that apply.)

1. Apushbutton switch
2. Brelay
3. Ctransistor
4. Dpotentiometer

The single-pole double-throw (SPDT) switch is a commonly used switching element. What does “single-pole double-throw” mean?

1. Ait routes one circuit to be connected to one of two other circuits
2. Bclearly, it simply connects or disconnects one circuit
3. Cclearly, it connects or disconnects two circuits
4. Dit routes two circuits each to one of their corresponding other two circuits

Which of the following components can protect other components in a circuit from overcurrent surges?

1. Afuse
2. BMOSFET
3. Cvacuum tube
4. Dcapacitor

Among the components used in assembling amateur transceivers, those typically marked with a rated current are: (Choose all that apply.)

1. Afuse
2. Bswitch
3. Crelay
4. Dpiezoelectric crystal

In amateur projects, fuses are often glass- or ceramic-bodied fuse cartridges used to enhance circuit safety. Useful lessons for their use include: (Choose all that apply.)

1. Awhen selecting a fuse cartridge, pay attention to its rated working voltage, rated current, and fusing speed
2. Binstall high-current fuse cartridges in a holder so they do not burst when blowing and damage nearby components
3. Cmount the power-line fuse holder on the chassis back panel as far as possible to simplify servicing
4. Dfit an RF filter on the fuse to prevent arcing when it blows and interfering with nearby amateur stations

A relay is a switch with electrical isolation, often used to control high-power or high-voltage circuits with low-power low-voltage signals. In amateur projects, relays also switch RF paths. Useful lessons for relay application include: (Choose all that apply.)

1. Awhen selecting a relay, consider the contact’s rated voltage and rated current
2. Bwhen using a relay for transmit/receive switching, switch it only after the transmitter is on standby (no RF present)
3. Cwhen choosing a relay to switch signals, consider its ability to pass small signals
4. Dwhen building HF or VHF equipment, one should as far as possible use microwave RF relays

If a switching device is used to control whether a relay’s armature coil is energized — for example, with the coil in the collector circuit of a transistor — which of the following may happen?

1. Athe instant the transistor turns off, its collector may be subjected to a high-voltage spike far above the supply voltage
2. Bthe instant the transistor turns on, its collector may be subjected to a high-voltage spike far above the supply voltage
3. Cthe instant the transistor turns off, its collector may be subjected to a current surge far larger than the on-state current
4. Dthe instant the transistor turns on, its collector may be subjected to a current surge far larger than the on-state current

If a switching device controls whether a relay’s armature coil is energized, a small capacitor or a reverse-biased diode is placed across the coil. Its purpose is:

1. Ato absorb the back-EMF induced in the coil at the moment the circuit turns off, protecting the switching device
2. Bto eliminate spark interference generated when the relay contacts open/close
3. Cto reduce the operating current through the switching device
4. Dto reduce wear of the relay

If a relay controls a DC load, we sometimes connect a small capacitor across the relay’s contacts. Its purpose is:

1. Ato suppress the electromagnetic interference caused by arcing when the contacts open/close
2. Bto absorb the back-EMF induced in the coil at turn-off, protecting the switching device
3. Cto reduce the operating current through the switching device
4. Dto reduce wear of the relay

Electromagnetic induction is the phenomenon where a conductor placed in a changing magnetic field develops an induced electromotive force. Its application scenarios include: (Choose all that apply.)

1. Atransformer
2. Bgenerator
3. CAC induction (asynchronous) motor
4. Dradio communication

The electromagnetic term “mutual inductance” (互感现象) means:

1. Athe phenomenon where, as the currents in two circuits vary, each induces an electromotive force in the other through magnetic-field coupling
2. Bthe phenomenon where the impedances of two connected components oppose the current flowing through each other
3. Cthe superposition of the electric fields of two charged parts
4. Dthe phenomenon where two electromagnetic waves of different frequencies superimpose in air and mix to produce interference

Why is a transformer’s iron core built from many insulated silicon-steel laminations of large cross-section and high permeability, rather than using a solid core like a relay armature?

1. Athe stacked laminations are insulated from each other, which reduces eddy-current loss
2. Bstacking the silicon steel reduces the transformer’s non-linear distortion
3. Cthe laminated process simplifies transformer assembly
4. Da transformer made with a solid core easily loosens and vibrates

For an ideal transformer, the turns ratio of primary to secondary determines the voltage ratio. Suppose an ideal transformer has 1100 primary turns and 110 secondary turns, the primary is connected to a 220 V AC source, and a 22 Ω resistor is placed in parallel across the secondary. Which of the following conclusions is correct? (Voltages and currents are RMS values.) (Choose all that apply.)

1. Athe secondary voltage is 22 V
2. Bthe secondary current is 1 A
3. Cthe primary impedance is 2.2 kΩ
4. Dthe transformer’s power consumption is 22 W

For an ideal transformer, the turns ratio determines the voltage ratio. Suppose an ideal transformer has 120 primary turns and 1800 secondary turns, the primary is connected to a 220 V AC source, and a 4.5 kΩ resistor is placed in parallel across the secondary. Which of the following conclusions is correct? (Voltages and currents are RMS values.) (Choose all that apply.)

1. Athe secondary voltage is 3300 V
2. Bthe primary current is 11 A
3. Cthe primary impedance is 20 Ω
4. Dthe transformer’s power consumption is 2.42 kVA

In RF circuits, one use of a transformer is impedance transformation. A certain HF transformer wound on a ferrite toroid has 3 primary turns and 6 secondary turns. Within its designed frequency and load-impedance range, which of the following is correct? (Choose all that apply.)

1. Ait can serve as a 1:4 or 4:1 impedance transformer; to use it as the latter, swap primary and secondary
2. Bit can serve as a 1:2 or 2:1 voltage transformer; to use it as the latter, swap primary and secondary
3. Cit can serve as a phase-inverting transformer with impedance transformation, by swapping the wiring order of the primary or secondary
4. Dit can match an antenna and convert the reactive part of the antenna impedance into a resistive part in proportion

If an antenna has an impedance of 450 Ω, what turns ratio transformer is needed to transform it to 50 Ω?

1. A3:1
2. B9:1
3. C450:1
4. D50:1

A transmission-line transformer is an RF transformer designed using transmission-line theory and is widely used in amateur projects. For example, a few twisted-pair turns through a toroid make a 1:4 impedance transformer. The advantages of this kind of transformer are: (Choose all that apply.)

1. Ait can achieve impedance matching over a very wide frequency band
2. Bit can be made into a balun (balanced-to-unbalanced converter)
3. Cit can be made into power-combining and power-splitting networks
4. Dit can realize frequency multiplication and division by integer ratios

Using a solid wire as a connection in an RF circuit at frequencies of tens of megahertz produces which phenomenon?

1. Athe current concentrates on the surface of the wire, with essentially no current inside
2. Bthe current density is uniformly distributed across the wire’s cross-section
3. Ccurrent exists both on the outer and inner layers, but in opposite directions
4. Dsurface current flows along the wire while inner current forms spiral eddies

For solid copper wire and a hollow copper tube of the same material, diameter, and length, how do their heat losses in an AC circuit compare?

1. Aat low frequency the solid wire has lower loss; at high frequency the two have the same loss
2. Bat low frequency the solid wire has higher loss; at high frequency the two have the same loss
3. Cat different frequencies the losses are not easily comparable and depend on cooling conditions
4. Dat any frequency the losses of the two are the same

A capacitor measures a capacitive reactance of 100 Ω at 50 Hz. One would infer its reactance at 5 MHz should be 0.001 Ω, but the measured value is significantly larger. This is because: (Choose all that apply.)

1. Aas frequency rises, the inductive reactance of the capacitor’s leads becomes non-negligible
2. Bas frequency rises, the capacitor’s dielectric loss gradually increases
3. Cthe instrument used has poor frequency response
4. Dthe capacitive-reactance formula no longer applies at high frequency

An inductor coil measures an inductive reactance of 10 Ω at 50 Hz. One would infer its reactance at 5 MHz should be about 1 MΩ, but the measured value is significantly smaller. This is because:

1. Aas frequency rises, the coil’s inter-winding distributed capacitance becomes non-negligible
2. Bthe instrument used has poor frequency response
3. Cthe inductive-reactance formula no longer applies at high frequency
4. Dthe coil’s wire loss causes non-linear distortion

Which of the following are active devices? (Choose all that apply.)

1. Asilicon rectifier diode
2. BSchottky diode
3. Cfield-effect transistor (FET)
4. Dbipolar junction transistor (BJT)

Which of the following components allows current to flow in only one direction?

1. Adiode
2. Bbattery
3. Ctransformer
4. Drelay

What are the two electrodes of a diode called?

1. Athey are called the positive and negative terminals, also known as the anode and cathode
2. Bthey are called the source and drain, also known as the injector and releaser
3. Cthey are called the cathode and plate, also known as the emitter and receiver
4. Dthey are called the gate and base, also known as the trigger and control electrodes

How can you identify the cathode (negative terminal) of a semiconductor diode by its appearance?

1. Aa ring or line mark is usually printed on the package near the cathode end
2. Bthe cathode is usually labeled with the words “负极” or “Cathode”
3. Cthe cathode lead is usually about 20% longer than the anode lead
4. Dthe cathode is usually near the key/marker and connected to an adjacent filament pin

What device does the abbreviation LED stand for?

1. Alight-emitting diode
2. Bliquid-crystal display (LCD)
3. Ccathode-ray tube (CRT)
4. Dbeam tetrode

Among the following devices, which can be used as an indicator lamp?

1. ALED
2. BBJT (bipolar junction transistor)
3. CTVS (transient-voltage-suppressor diode)
4. DSCR (silicon-controlled rectifier / thyristor)

What must be observed when connecting an LED to a DC supply?

1. Aconnect it with forward polarity and in series with a current-limiting resistor
2. Bconnect it with reverse polarity and in series with a current-limiting resistor
3. Cpolarity does not matter, but a current-limiting resistor must be connected in parallel
4. Dconnect it directly to the DC supply with forward polarity

Which of the following components can convert alternating current into pulsating direct current?

1. Adiode rectifier
2. Bpower transformer
3. Ccomparator/amplifier
4. Demitter follower

The forward conduction voltage drop of a silicon rectifier diode is approximately:

1. A0.7 V
2. B0.3 V
3. Ctens of millivolts
4. D1000 V

When reading a circuit diagram or running a circuit simulation, if you see the symbol “BJT”, it denotes:

1. Abipolar junction transistor
2. Bdual-gate field-effect transistor
3. Cjunction field-effect transistor (JFET)
4. Ddouble-base diode (unijunction transistor)

The three basic electrodes of a field-effect transistor are:

1. Asource, gate, drain
2. Bcathode, grid, plate
3. Cemitter, base, collector
4. Dcathode, gate, anode

The three basic electrodes of a bipolar junction transistor are:

1. Aemitter, base, collector
2. Bcathode, grid, plate
3. Csource, gate, drain
4. Dcathode, gate, anode

The three basic electrodes of a vacuum triode are:

1. Acathode, grid, plate (anode)
2. Bemitter, base, collector
3. Csource, gate, drain
4. Dcathode, gate, anode

What is the minimum number of pins a vacuum triode must have?

1. A4
2. B2
3. C3
4. D5

The most commonly used parameter, unit, and symbol describing the amplification ability of a field-effect transistor are:

1. Atransconductance (mutual conductance); unit milliamperes per volt (mA/V); symbol “gm”
2. Bcurrent gain; dimensionless; symbol “β”
3. Ctransconductance; unit “times”; symbol “A”
4. Dvoltage gain; dimensionless; symbol “k”

The most commonly used parameter, unit, and symbol describing the amplification capability of a bipolar transistor are:

1. Acurrent gain; no unit (dimensionless); symbol “β”
2. Btransconductance (mutual conductance); unit milliampere per volt; symbol “gm”
3. Ctransconductance (mutual conductance); unit “times”; symbol “A”
4. Dvoltage gain; no unit (dimensionless); symbol “k”

The most commonly used parameter, unit, and symbol describing the amplification capability of an electronic triode (vacuum tube) are:

1. Atransconductance (mutual conductance); unit milliampere per volt; symbol “gm”
2. Bcurrent gain; no unit (dimensionless); symbol “β”
3. Ctransconductance (mutual conductance); unit “times”; symbol “A”
4. Dvoltage gain; no unit (dimensionless); symbol “k”

If the control electrodes of devices are arranged in order of increasing input impedance, they could be:

1. Athe base of a bipolar transistor, the gate of a junction field-effect transistor, the gate of an insulated-gate field-effect transistor
2. Bthe base of a bipolar transistor, the gate of an insulated-gate field-effect transistor, the gate of a junction field-effect transistor
3. Cthe gate of an insulated-gate field-effect transistor, the base of a bipolar transistor, the gate of a junction field-effect transistor
4. Dthe gate of a junction field-effect transistor, the base of a bipolar transistor, the gate of an insulated-gate field-effect transistor

Which of the following components can be used to achieve the function of controlling a larger current with a smaller current? (Choose all that apply.)

1. Atransistor
2. Brelay
3. Cresistor
4. Dbattery

Which of the following components can be used both as an electronic switch and as an amplifier?

1. Atransistor
2. Bpotentiometer
3. Csingle-pole double-throw switch
4. Dvoltmeter

An integrated circuit refers to:

1. Aa device made by integrating a large number of components of a circuit onto a single chip
2. Ba circuit composed of multiple relays with logic-operation capability
3. Ca circuit composed of multiple resistors or capacitors with differentiation or integration functions
4. Da power-combining circuit made of multiple windings based on the transformer principle

The basic concept of an ideal operational amplifier is: (Choose all that apply.)

1. Awithout negative feedback, i.e., operating open-loop, its amplification factor is infinite
2. Bthis amplifier has both positive and negative polarity input terminals, and its input impedance is infinite
3. Cby “ideal” it actually means a common-emitter transistor amplifier whose internal noise is zero
4. Dby “ideal” it actually means a field-effect transistor amplifier whose output voltage amplitude has no upper limit

What type of integrated circuit does an integrated operational amplifier belong to?

1. Aanalog integrated circuit
2. Bmonolithic microwave integrated circuit
3. Cdigital integrated circuit
4. Dprogrammable digital logic array

Some integrated circuits commonly seen in amateur radio projects, such as operational amplifiers and microprocessors, sometimes have letter suffixes added after the marked model number, e.g., SIP, DIP, SOT, SOP, SSOP, QFP, etc. They are used to indicate:

1. Athe package form of the device
2. Bthe operating temperature range of the device
3. Cthe input/output voltage level range of the device
4. Dthe operating frequency range of the device