CRAC Bilingual Manual › Part: Electrical Basics for Amateur Radio
CRAC Bilingual Exam Manual (Class A / B / C) | 中国业余无线电台操作技术能力验证英中对照手册
This section covers Conductors and Current with 72 bilingual questions from the CRAC 2025 question bank. Each question shows the original Chinese (left) and the English translation (right). The correct answer is highlighted in green, followed by a Knowledge Point Analysis and Candidate Tips covering US–China differences, common pitfalls, and real on-air practice.
Class badges ABC indicate which license-class syllabus includes each question. Class A is the entry level, Class B adds HF privileges, and Class C is the advanced level.
导体是易于传导电流的物质或材料。以下关于导体的正确描述是：
- A导体中存在大量的可自由移动的电子或离子，施加电压可产生电流
- B多数金属都是导电性能优良的导体，比如银、铜和铝
- C有些金属在高温下呈现零电阻特性，成为超导体
- D某些金属具有压电效应，可用来制作电声元件
A conductor is a substance or material that readily conducts electric current. Which of the following descriptions of conductors is correct? (Choose all that apply.)
- AA conductor contains a large number of freely movable electrons or ions; applying a voltage can produce a current
- BMost metals are excellent conductors, such as silver, copper, and aluminum
- CSome metals exhibit zero resistance at high temperature, becoming superconductors
- DCertain metals have the piezoelectric effect and can be used to make electroacoustic components
A conductor has many free electrons/ions and conducts under voltage (A), and most metals (silver, copper, aluminum) are good conductors (B). C is false — superconductivity occurs at very low, not high, temperature; D is false — piezoelectricity is a crystal property, not typical of “metals” as conductors.
US–China difference: N/A — conductor physics is universal.
Common pitfall: Believing superconductors appear at high temperature, or that metals are piezoelectric.
Real on-air practice: Your feed line’s copper center conductor is the everyday conductor at work.
关于导体，以下说法正确的是：
- A霓虹灯中电离发光的气体是导体
- B酸、碱、盐的水溶液是导体
- C石墨是导体
- D云母是导体
Regarding conductors, which of the following statements is correct? (Choose all that apply.)
- AThe ionized, glowing gas in a neon lamp is a conductor
- BAcid, alkali, and salt aqueous solutions are conductors
- CGraphite is a conductor
- DMica is a conductor
Ionized gas conducts (A), electrolyte solutions conduct via ions (B), and graphite (a form of carbon) conducts (C). Mica (D) is an insulator/dielectric, not a conductor.
US–China difference: N/A — same conductor classifications apply.
Common pitfall: Mistaking mica (a classic insulator/dielectric) for a conductor.
Real on-air practice: Mica sheets are used as insulation inside tuning capacitors; graphite is used in some resistive loads.
绝缘体是不易传导电流的物质或材料。以下关于绝缘体的正确描述是：
- A分子中正负电荷紧密束缚，可自由移动的带电粒子极少，呈现很大的电阻
- B绝缘体也称电介质。有些电介质可用来制作电容器，比如陶瓷和聚苯乙烯
- C随着所加电场的增强，绝缘体会突然导电而成为导体。这种现象称为击穿
- D随着温度的升高，绝缘体的绝缘程度下降。使用绝缘体应当关注工作温度
An insulator is a substance or material that does not readily conduct electric current. Which of the following descriptions of insulators is correct? (Choose all that apply.)
- AIn the molecule, positive and negative charges are tightly bound; there are very few freely movable charged particles, presenting very large resistance
- BAn insulator is also called a dielectric. Some dielectrics can be used to make capacitors, such as ceramic and polystyrene
- CAs the applied electric field increases, the insulator suddenly conducts and becomes a conductor. This phenomenon is called breakdown
- DAs temperature rises, the insulating property of the insulator decreases. One should pay attention to the operating temperature when using insulators
All four are correct: insulators bind charges tightly and show high resistance (A); they are dielectrics usable in capacitors like ceramic/polystyrene (B); excessive field causes breakdown into conduction (C); and heating reduces insulation, so temperature matters (D).
US–China difference: N/A — insulator/dielectric behavior is universal.
Common pitfall: Forgetting that insulators can break down and are temperature-sensitive.
Real on-air practice: Coax dielectric (e.g., PTFE) and ceramic capacitor insulation are everyday insulators in your station.
以下哪些可以用作绝缘材料？
- A工程塑料
- B酚醛树脂
- C二氧化硅
- D二氧化锡
Which of the following can be used as insulating materials? (Choose all that apply.)
- Aengineering plastics
- Bphenolic resin (Bakelite)
- Csilicon dioxide
- Dtin dioxide
Engineering plastics (A), phenolic resin (B), and silicon dioxide (C, e.g., glass/quartz) are insulators. Tin dioxide (D, SnO₂) is a semiconductor/conductive oxide, not an insulator, so it is excluded.
US–China difference: N/A — same materials classify as insulators worldwide.
Common pitfall: Including tin dioxide, which is a transparent conductive oxide, not an insulator.
Real on-air practice: Phenolic (Bakelite) enclosures and glass-insulated feed-throughs are common.
“击穿”是指施加于绝缘介质上的电压高于一定值时，部分介质突然变成导体，导致介质的电阻陡然下降的一种现象。以下哪些是对击穿现象的描述？
- A电路中的电容在工作电压显著超过标称耐压后变成导体，造成电路短路
- B天线调谐器工作时，可变电容的极板间出现电弧，导致发射机告警保护
- C验电笔中的氖灯发光
- D台灯里的卤钨灯发光
“Breakdown” refers to a phenomenon where, when the voltage applied to an insulating medium exceeds a certain value, part of the medium suddenly becomes a conductor, causing the medium’s resistance to drop sharply. Which of the following are descriptions of the breakdown phenomenon? (Choose all that apply.)
- AA capacitor in a circuit becomes a conductor after its operating voltage significantly exceeds its rated withstand voltage, causing a short circuit
- BWhen an antenna tuner is operating, an arc appears between the plates of a variable capacitor, causing the transmitter to alarm and protect itself
- CThe neon lamp in a test pencil glows
- DThe halogen-tungsten lamp in a desk lamp glows
Breakdown is dielectric failure into conduction: an overvolted capacitor shorting (A), an arc across a tuner capacitor (B), and a neon lamp ionizing/glowing under its breakdown voltage (C) all illustrate it. D is ordinary incandescent heating, not breakdown, so it is excluded per the key.
US–China difference: N/A — dielectric breakdown physics is the same.
Common pitfall: Confusing normal incandescence (D) with dielectric breakdown.
Real on-air practice: Keep RF voltages within your tuner capacitor’s plate spacing to avoid arcing/breakdown.
业余无线电设备中的射频部件积灰或受潮后，即使没有击穿或漏电，也可能因绝缘体的物理性质发生改变而意外产生：
- A介质损耗
- B涡流损耗
- C磁滞损耗
- D磁阻损耗
After the RF components in amateur radio equipment accumulate dust or become damp, even without breakdown or leakage, they may unexpectedly produce, due to a change in the insulator’s physical properties:
- Adielectric loss
- Beddy-current loss
- Chysteresis loss
- Dmagnetic-reluctance loss
Dust/moisture change an insulator’s (dielectric’s) properties, causing dielectric loss (介质损耗) — energy dissipated in the dielectric under RF (A). Eddy-current (B) and hysteresis (C) losses belong to magnetic cores; magnetic-reluctance loss (D) is not the effect described.
US–China difference: N/A — dielectric loss is a universal RF effect.
Common pitfall: Attributing the loss to magnetic-core effects rather than the dielectric.
Real on-air practice: Keep RF insulators (coax ends, antenna bases) clean and dry to avoid heating/dielectric loss.
半导体是导电能力介于导体与绝缘体之间的一类物质或材料。对半导体的正确描述是：
- A导电特性易于控制。例如，温度、光照或电场的少许变化可显著改变材料的导电性
- B半导体可分为本征半导体和杂质半导体。后者又有P型和N型之分
- CP型和N型半导体的交界面称为PN结，具有内建电动势和单向导电性
- D硅、锗等半导体材料可用来制作晶体管或集成电路
A semiconductor is a class of substance or material whose conducting ability lies between that of conductors and insulators. Which of the following descriptions of semiconductors is correct? (Choose all that apply.)
- AIts conducting properties are easy to control. For example, a slight change in temperature, illumination, or electric field can significantly alter the material’s conductivity
- BSemiconductors can be divided into intrinsic semiconductors and impurity semiconductors. The latter is further divided into P-type and N-type
- CThe junction between P-type and N-type semiconductors is called a PN junction, which has a built-in electromotive force and one-way (unilateral) conductivity
- DSemiconductor materials such as silicon and germanium can be used to make transistors or integrated circuits
All four are correct: semiconductors’ conductivity is controllable (A), they are intrinsic vs impurity (P/N) types (B), the P-N junction has a built-in EMF and rectifying (one-way) behavior (C), and silicon/germanium build transistors and ICs (D).
US–China difference: N/A — semiconductor fundamentals are universal.
Common pitfall: None of the four is wrong; candidates sometimes wrongly doubt one.
Real on-air practice: Your transceiver’s silicon/GaN chips are all built from these semiconductor principles.
下列哪些器件由半导体材料制成？
- A双极型三极管
- B氮化镓三极管
- CLDMOS三极管
- D电真空三极管
Which of the following devices are made of semiconductor material? (Choose all that apply.)
- Abipolar transistor
- Bgallium-nitride (GaN) transistor
- CLDMOS transistor
- Dvacuum-tube triode
Bipolar (A), gallium-nitride (B), and LDMOS (C) transistors are all solid-state semiconductor devices. A vacuum-tube triode (D) is not semiconductor — it is an electron-tube device.
US–China difference: N/A — device categories are the same worldwide.
Common pitfall: Including the vacuum tube, which is not a semiconductor device.
Real on-air practice: Modern HF transceivers use LDMOS or GaN final transistors; older gear used tubes.
静电放电是一种常见电磁现象，时刻伴随日常生活。但是，较强的静电放电却足以损坏电子设备甚至危及人身，需要预防。以下所述与静电有关的是：
- A刮风时，斜拉天线上出现的直流高压
- B雷雨时，云层中积蓄的巨大能量
- C收信时，接收机收到的各种QRN
- D发话时，电台馈送到天线的射频能量
Electrostatic discharge (ESD) is a common electromagnetic phenomenon that accompanies daily life at all times. However, strong ESD can damage electronic equipment or even endanger human life and must be prevented. Which of the following are related to static electricity? (Choose all that apply.)
- Athe DC high voltage that appears on guyed antennas when wind blows
- Bthe huge energy accumulated in clouds during thunderstorms
- Cthe various QRN received by a receiver during reception
- Dthe RF energy fed from the radio to the antenna when transmitting
Static-related phenomena include charge buildup on wind-blown guy wires (A), thundercloud charge (B), and atmospheric/static noise QRN heard on receive (C). RF energy fed to the antenna while transmitting (D) is intentional radio emission, not static electricity.
US–China difference: N/A — ESD and QRN concepts are the same.
Common pitfall: Confusing transmitted RF energy with static discharge.
Real on-air practice: You hear QRN (static crashes) on HF during storms; grounded antenna static bleeds protect gear.
如果将导体置于静电场中，导体将呈现如下特点：
- A静电平衡后，导体是等势体，内部场强为零，外表面出现电荷
- B外表面曲率很小时，导体表面的电荷会高度聚集。这可能形成尖端放电
- C静电平衡后，导体是等势体，内部电荷与外表面电荷极性相反
- D外表面曲率很大时，导体表面的电荷会高度聚集。这可能形成尖端放电
If a conductor is placed in an electrostatic field, the conductor will exhibit the following characteristics: (Choose all that apply.)
- Aafter electrostatic equilibrium, the conductor is an equipotential body, the internal field is zero, and charge appears on the outer surface
- Bwhen the outer-surface curvature is very small, the charge on the conductor’s surface will be highly concentrated. This may form point (tip) discharge
- Cafter electrostatic equilibrium, the conductor is an equipotential body, and the internal charge is opposite in polarity to the outer-surface charge
- Dwhen the outer-surface curvature is very large, the charge on the conductor’s surface will be highly concentrated. This may form point (tip) discharge
Statement A is correct physics: at electrostatic equilibrium a conductor is equipotential, internal field is zero, and excess charge resides on the outer surface. The official answer key marks A and B. Study note: in real physics, surface charge concentrates where curvature is large (sharp points), so option D actually states the correct tip-discharge condition; the source key nonetheless marks B, so memorize the keyed answer.
US–China difference: N/A — electrostatic-equilibrium physics is universal.
Common pitfall: Thinking charge sits inside the conductor; it moves to the outer surface.
Real on-air practice: Keep antenna tips and connectors smooth/burrd-free to avoid corona and RF arc-over.
直流电（DC）是以电荷的运动方向始终不变来定义的。关于直流电，以下描述正确的是：
- A直流电源的输出端有正负极之分
- B电池提供的是直流电
- C直流电压通常为13.8伏。这样的低压即使短路也没什么危害
- D脉动直流电不含交流成分，因为电荷的运动方向始终不变
Direct current (DC) is defined by the direction of charge motion never changing. Which of the following descriptions of direct current is correct? (Choose all that apply.)
- AThe output terminals of a DC power supply have positive and negative poles
- BA battery provides direct current
- CDC voltage is typically 13.8 volts. Such low voltage is harmless even if short-circuited
- DPulsating direct current contains no AC component, because the direction of charge motion never changes
DC has fixed polarity terminals (A) and a battery supplies DC (B). C is false — 13.8 V can deliver dangerous short-circuit current; D is false — pulsating DC still contains an AC (ripple) component even though its average direction is fixed.
US–China difference: N/A — DC definitions are identical.
Common pitfall: Thinking 13.8 V is “safe” to short; it can melt wiring and cause fires.
Real on-air practice: Your station power supply delivers 13.8 V DC to the transceiver; fuse it properly.
交流电（AC）是以电荷的运动方向随时间交替变化来定义的。关于交流电，以下描述正确的是：
- A交流电源的输出端没有正负极之分，因为极性总在交替变化
- B220V市电是一种交流电。由于不需区分正负极，所以火线和零线可以混用
- C交流电均为纯正弦波，仅包含单一频率成分
- D业余电台所接收的信号不是交流电。那是复杂波形信号，也就是”复信号”
Alternating current (AC) is defined by the direction of charge motion alternating with time. Which of the following descriptions of alternating current is correct?
- AThe output terminals of an AC power supply have no fixed positive/negative poles, because the polarity is always alternating
- B220 V mains is a kind of AC. Since there is no need to distinguish positive/negative, the live wire and neutral wire can be used interchangeably
- CAC is always a pure sine wave, containing only a single frequency component
- DThe signals received by an amateur station are not AC. They are complex-waveform signals, i.e., ‘complex signals’
AC polarity alternates, so an AC source has no fixed +/− terminals (A). B is false — live (hot) and neutral must not be swapped; C is false — AC can be non-sinusoidal/multi-frequency; D is false — received RF is an AC signal.
US–China difference: US mains is 120 V; China’s is 220 V — both are AC with hot/neutral that must not be reversed.
Common pitfall: Assuming live and neutral are interchangeable; they are not.
Real on-air practice: Your AC mains feeds a power supply that makes 13.8 V DC for the radio.
以下哪一个术语可以用来描述交流电每秒改变极性的次数？
- A频率
- B速率
- C波长
- D脉率
Which of the following terms can be used to describe the number of times per second that alternating current changes polarity?
- Afrequency
- Brate
- Cwavelength
- Dpulse rate
The number of polarity reversals per second is the frequency (频率), measured in hertz (A). Rate (B), wavelength (C), and pulse rate (D) describe other quantities.
US–China difference: N/A — frequency is defined the same way.
Common pitfall: Confusing frequency with wavelength or pulse rate.
Real on-air practice: 50 Hz mains (China) vs 60 Hz (US) — both described by frequency.
业余无线电爱好者经常提及的”波长”与无线电波的频率有什么关系？
- A波长为光速与频率之比；频率越高，波长越短
- B波长与真空有些关联，但是在现实生活中无用
- C很明显，波长为频率的1/4。这个常数应当牢记
- D很明显，波长为频率的4倍。这个常数应当牢记
What is the relationship between the “wavelength” frequently mentioned by amateur radio operators and the frequency of radio waves?
- AWavelength is the ratio of the speed of light to frequency; the higher the frequency, the shorter the wavelength
- BWavelength has some connection to vacuum, but is useless in real life
- CObviously, wavelength is 1/4 of frequency. This constant should be memorized
- DObviously, wavelength is 4 times frequency. This constant should be memorized
Wavelength λ = c / f (speed of light ÷ frequency); higher frequency means shorter wavelength (A). B (useless) is false — amateurs use wavelength to name bands (e.g., “20 m”); C and D invent false fixed ratios.
US–China difference: N/A — λ = c/f is universal; bands are named by wavelength in both countries.
Common pitfall: Thinking wavelength is a fixed fraction of frequency; it is inversely proportional.
Real on-air practice: “I’m on 20 meters” means ~14 MHz; you compute antenna length from λ.
物理量”电动势”描述的是：
- A电子器件或装置将某种形式的能量转化为电能的能力
- B加在电路两端的电源驱动电子流动的力量大小
- C单位时间内流过电路的电子数量
- D电源所能供应的电子数量最大值
The physical quantity “electromotive force (EMF)” describes:
- Athe ability of an electronic device or apparatus to convert some form of energy into electrical energy
- Bthe magnitude of the force driving electrons to flow, applied by the power source across the circuit
- Cthe number of electrons flowing through the circuit per unit time
- Dthe maximum number of electrons the power source can supply
电动势 (electromotive force, EMF) is the ability of a source to convert other energy forms into electrical energy (A). B describes voltage; C describes current; D is not a standard quantity.
US–China difference: N/A — EMF is defined the same way.
Common pitfall: Confusing EMF (energy conversion) with voltage (driving force across a circuit).
Real on-air practice: A battery’s EMF (e.g., 12 V) is what it can supply before internal losses.
物理量”电压”描述的是：
- A加在电路两端的电源驱动电子流动的力量大小
- B电子器件或装置将其它形式的能量转化为电能的能力
- C单位时间内流过电路的电子数量
- D电源所能供应的电子数量最大值
The physical quantity “voltage” describes:
- Athe magnitude of the force driving electrons to flow, applied by the power source across the two ends of a circuit
- Bthe ability of an electronic device or apparatus to convert other forms of energy into electrical energy
- Cthe number of electrons flowing through the circuit per unit time
- Dthe maximum number of electrons the power source can supply
电压 (voltage) is the electric potential difference that drives electrons through a circuit (A). B is EMF; C is current; D is not a standard quantity.
US–China difference: N/A — voltage is defined the same way.
Common pitfall: Swapping voltage with EMF or current.
Real on-air practice: Your radio runs on 13.8 V DC; your coax carries RF voltage between center and shield.
正弦交流电压或电流的峰值（peak value）是指：（”x＾m”表示”x的m次方”）
- A从零点算起的最大值
- B一个周期内瞬时值的平均值乘以2＾(1/2)
- C负半周最大幅度与正半周最大幅度的平均值
- D负半周最大幅度与正半周最大幅度的差值的二次方
The peak value of a sinusoidal AC voltage or current refers to: (“x＾m” means “x to the power m”)
- Athe maximum value measured from zero
- Bthe average of the instantaneous values within one period multiplied by 2＾(1/2)
- Cthe average of the negative-half-cycle maximum amplitude and the positive-half-cycle maximum amplitude
- Dthe square of the difference between the negative-half-cycle maximum amplitude and the positive-half-cycle maximum amplitude
峰值 (peak value) is the maximum instantaneous magnitude measured from zero (A). B confuses peak with RMS (peak × 1/√2 gives RMS, not the other way); C and D are not definitions.
US–China difference: N/A — peak value definition is universal.
Common pitfall: Mixing peak with RMS or average.
Real on-air practice: RF peak envelope power (PEP) is derived from the voltage peak on a 50 Ω load.
正弦交流电压或电流的峰-峰值（peak-to-peak value）是指：
- A从负半周峰值到正半周峰值之间的差值
- B从零点算起的最大值
- C负半周最大幅度与正半周最大幅度的差值的二次方
- D负半周最大幅度与正半周最大幅度的差值的平方根
The peak-to-peak value of a sinusoidal AC voltage or current refers to:
- Athe difference from the negative-half-cycle peak to the positive-half-cycle peak
- Bthe maximum value measured from zero
- Cthe square of the difference between the negative-half-cycle maximum amplitude and the positive-half-cycle maximum amplitude
- Dthe square root of the difference between the negative-half-cycle maximum amplitude and the positive-half-cycle maximum amplitude
峰-峰值 (peak-to-peak value) is the total span from the negative peak to the positive peak (A). B is the peak value; C and D apply spurious powers/roots.
US–China difference: N/A — peak-to-peak is defined identically.
Common pitfall: Calling the peak (from zero) the peak-to-peak value.
Real on-air practice: Oscilloscopes display RF/audio waveforms in peak-to-peak volts.
任意交流电压的有效值（RMS voltage）是指：（”x＾m”表示”x的m次方”）
- A在同一电阻上可以转换出与该交流电压效果相同的热量的直流电压
- B最终转换成在应用场景中真正发挥作用的有效能量的那部分电压值
- C电压的平均值乘以2＾(1/2)
- D电压的峰值除以2＾(1/2)
The RMS (root-mean-square) voltage of any AC voltage refers to: (“x＾m” means “x to the power m”)
- Athe DC voltage that, across the same resistor, would produce the same amount of heat as this AC voltage
- Bthe portion of voltage that ultimately converts into truly useful effective energy in the application scenario
- Cthe average value of the voltage multiplied by 2＾(1/2)
- Dthe peak value of the voltage divided by 2＾(1/2)
有效值 (RMS voltage) is the DC voltage that dissipates the same heat in the same resistor (A) — the heating-equivalent value. Note: for a pure sine wave, RMS = peak/√2 (which is option D phrased for sine waves only), but the general definition is the heating equivalence in A, which the key marks.
US–China difference: N/A — RMS is defined identically; US mains 120 V is RMS.
Common pitfall: Thinking RMS = average × √2; that only holds for a sine’s peak relation.
Real on-air practice: Your 13.8 V DC and 120/220 V AC are RMS/DC values used for power heating math.
物理量”电流”描述的是：
- A单位时间内流过电路的电子数量
- B电源所能供应的电子数量最大值
- C通电后流过电路的电子数量
- D电子在导体中的运动速度
The physical quantity “current” describes:
- Athe number of electrons flowing through the circuit per unit time
- Bthe maximum number of electrons the power source can supply
- Cthe number of electrons flowing through the circuit after power is applied
- Dthe speed of electrons moving in the conductor
电流 (current) is charge flow per unit time — here described as electrons passing per unit time (A). B is not a standard quantity; C lacks the “per unit time” rate; D is drift speed, not current.
US–China difference: N/A — current is defined the same way.
Common pitfall: Confusing current (a rate) with total charge or electron speed.
Real on-air practice: Your radio draws a few amps of DC current on transmit.
物理量”电阻”描述的是：
- A电路从一点到另一点阻碍电流通过的能力大小
- B电子克服电路阻力所需的能量大小
- C电路阻碍电流通过所消耗的能量大小
- D电路阻断电流所需的过渡时间
The physical quantity “resistance” describes:
- Athe magnitude of a circuit’s ability to impede the passage of current from one point to another
- Bthe magnitude of the energy required for electrons to overcome the circuit’s resistance
- Cthe magnitude of the energy consumed by the circuit in impeding current passage
- Dthe transition time required for the circuit to block current
电阻 (resistance) is a circuit’s opposition to current flow between two points (A). B and C describe energy (that is power dissipation, not resistance itself); D describes a time, which resistance is not.
US–China difference: N/A — resistance is defined the same way.
Common pitfall: Confusing resistance (opposition) with power dissipated.
Real on-air practice: A dummy load presents a known resistance (e.g., 50 Ω) to your transmitter.
物理量”功率”描述的是：
- A电流在单位时间内所做的功
- B电子通过电路所获得的能量大小
- C负载总共消耗的能量
- D电源所能供应的电子数量最大值
The physical quantity “power” describes:
- Athe work done by current per unit time
- Bthe energy obtained by electrons passing through the circuit
- Cthe total energy consumed by the load
- Dthe maximum number of electrons the power source can supply
功率 (power) is work (energy) per unit time — here, the work done by current per unit time (A). B and C are energy (not rate); D is not a quantity of power.
US–China difference: N/A — power is defined the same way.
Common pitfall: Confusing power (a rate) with total energy.
Real on-air practice: Your license limits transmit power (e.g., 25 W for Class A); that is power, not energy.
直流电路欧姆定律是说：
- A流过电阻的电流I与电阻两端的电压U成正比，与阻值R成反比
- B电阻两端的电压U与流过电阻的电流I成正比，与阻值R成正比
- C流过电阻的电流I与电阻两端的电压U成正比，与阻值R成正比
- D电阻两端的电压U与流过电阻的电流I成正比，与阻值R成反比
Ohm’s law for DC circuits states: (Choose all that apply.)
- AThe current I flowing through a resistor is directly proportional to the voltage U across the resistor and inversely proportional to the resistance R
- BThe voltage U across the resistor is directly proportional to the current I flowing through it and directly proportional to the resistance R
- CThe current I flowing through a resistor is directly proportional to the voltage U across the resistor and directly proportional to the resistance R
- DThe voltage U across the resistor is directly proportional to the current I flowing through it and inversely proportional to the resistance R
Ohm’s law: I = U/R, so current is proportional to voltage and inversely proportional to resistance (A); equivalently U = I·R, so voltage is proportional to both current and resistance (B). C wrongly makes current proportional to R; D wrongly makes voltage inversely proportional to R.
US–China difference: N/A — Ohm’s law is identical worldwide.
Common pitfall: Reversing the proportionality between voltage/current and resistance.
Real on-air practice: A 50 Ω dummy load at 10 V DC draws 0.2 A — straight from Ohm’s law.
在电路中不受电阻阻碍的电流，种类如下：
- A不存在
- B射频电流
- C音频电流
- D直流电流
The kinds of current that are not impeded by resistance in a circuit are:
- Anone exist
- BRF current
- Caudio current
- DDC current
Every real current encounters resistance (including RF, audio, and DC), so there is no kind of current free of resistive opposition (A). B/C/D all do experience resistance.
US–China difference: N/A — all currents meet resistance.
Common pitfall: Thinking RF or DC somehow bypasses resistance.
Real on-air practice: Even your feed line has loss (resistance), attenuating the RF current slightly.
术语”阻抗”描述的是：
- A电路从一点到另一点对交流电流阻碍作用的统称
- B电路从一点到另一点阻断直流电流，通过交流电流的能力大小
- C电路从一点到另一点阻断交流电流，通过直流电流的能力大小
- D电路从一点到另一点阻断特定频率交流电流的能力大小
The term “impedance” describes:
- Athe general term for a circuit’s opposition to alternating current from one point to another
- Ba circuit’s ability to block DC current and pass AC current from one point to another
- Ca circuit’s ability to block AC current and pass DC current from one point to another
- Da circuit’s ability to block AC current of a specific frequency from one point to another
阻抗 (impedance) is the general AC opposition a circuit presents between two points — combining resistance and reactance (A). B describes a capacitor-like behavior, C an inductor-like behavior, D a filter behavior; none is the general definition.
US–China difference: N/A — impedance is defined the same way.
Common pitfall: Equating impedance with a specific blocking/passing function rather than general AC opposition.
Real on-air practice: You match your 50 Ω antenna impedance to the radio for maximum power transfer.
电动势的单位是：
- A伏（特）
- B安（培）
- C瓦（特）
- D欧（姆）
The unit of electromotive force is:
- Avolt
- Bampere
- Cwatt
- Dohm
电动势 (EMF) is measured in volts (伏/特) (A) — it is a voltage-like quantity. Ampere is current, watt is power, ohm is resistance.
US–China difference: N/A — the volt is the international unit.
Common pitfall: Assigning EMF the ohm or watt unit.
Real on-air practice: A 12 V battery has an EMF of 12 V.
电压的单位是：
- A伏（特）
- B安（培）
- C瓦（特）
- D欧（姆）
The unit of voltage is:
- Avolt
- Bampere
- Cwatt
- Dohm
电压 (voltage) is measured in volts (伏/特) (A).
US–China difference: N/A — the volt is universal.
Common pitfall: Mixing up the units of voltage/current/power/resistance.
Real on-air practice: Coax carries RF voltage; your PSU supplies 13.8 V.
电流的单位是：
- A安（培）
- B伏（特）
- C瓦（特）
- D欧（姆）
The unit of current is:
- Aampere
- Bvolt
- Cwatt
- Dohm
电流 (current) is measured in amperes (安/培) (A).
US–China difference: N/A — the ampere is universal.
Common pitfall: Confusing ampere with volt or watt.
Real on-air practice: Transmitting draws several amperes from your 13.8 V supply.
电阻的单位是：
- A欧（姆）
- B安（培）
- C伏（特）
- D瓦（特）
The unit of resistance is:
- Aohm
- Bampere
- Cvolt
- Dwatt
电阻 (resistance) is measured in ohms (欧/姆) (A).
US–China difference: N/A — the ohm is universal.
Common pitfall: Mixing ohm with volt/ampere/watt.
Real on-air practice: A 50 Ω coax and a 50 Ω dummy load both use ohms.
阻抗的单位是：
- A欧（姆）
- B安（培）
- C伏（特）
- D瓦（特）
The unit of impedance is:
- Aohm
- Bampere
- Cvolt
- Dwatt
阻抗 (impedance) is measured in ohms (欧/姆) (A), the same unit as resistance.
US–China difference: N/A — the ohm is universal.
Common pitfall: Forgetting impedance shares the ohm unit with resistance.
Real on-air practice: Antenna impedance of 50 Ω must match the 50 Ω radio.
功率的单位是：
- A瓦（特）
- B安（培）
- C伏（特）
- D欧（姆）
The unit of power is:
- Awatt
- Bampere
- Cvolt
- Dohm
功率 (power) is measured in watts (瓦/特) (A).
US–China difference: N/A — the watt is universal.
Common pitfall: Mixing watt with volt/ampere/ohm.
Real on-air practice: Your license caps transmit power; you set it in watts on the radio.
频率的单位是：
- A赫（兹）
- B亨（利）
- C法（拉）
- D库（伦）
The unit of frequency is:
- Ahertz
- Bhenry
- Cfarad
- Dcoulomb
频率 (frequency) is measured in hertz (赫/兹) (A). Henry is inductance, farad is capacitance, coulomb is charge.
US–China difference: N/A — the hertz is universal.
Common pitfall: Confusing hertz with henry/farad/coulomb.
Real on-air practice: You tune to 14.070 MHz (hertz, ×10⁶) for FT8.
在法定计量单位中，词头k的数学意义和文字含义分别为：（”x＾m”表示”x的m次方”）
- A10＾3，千
- B10＾(-3)，毫
- C10＾6，兆
- D10＾(-6)，微
In the legal system of units, the prefix k has the following mathematical meaning and verbal meaning respectively: (“x＾m” means “x to the power m”)
- A10＾3, kilo
- B10＾(−3), milli
- C10＾6, mega
- D10＾(−6), micro
The prefix k (kilo, 千) means 10³ (A). Milli is 10⁻³, mega is 10⁶, micro is 10⁻⁶ (B/C/D are other prefixes).
US–China difference: N/A — SI prefixes are identical worldwide.
Common pitfall: Confusing k (10³) with M (10⁶) or m (10⁻³).
Real on-air practice: 144 MHz = 144 × 10⁶ Hz; 1 kW = 1000 W.
在法定计量单位中，词头m的数学意义和文字含义分别为：（”x＾m”表示”x的m次方”）
- A10＾(-3)，毫
- B10＾3，千
- C10＾6，兆
- D10＾(-6)，微
In the legal system of units, the prefix m has the following mathematical meaning and verbal meaning respectively: (“x＾m” means “x to the power m”)
- A10＾(−3), milli
- B10＾3, kilo
- C10＾6, mega
- D10＾(−6), micro
The prefix m (milli, 毫) means 10⁻³ (A). Kilo is 10³, mega is 10⁶, micro is 10⁻⁶ (B/C/D are other prefixes).
US–China difference: N/A — SI prefixes are identical worldwide.
Common pitfall: Confusing m (milli, 10⁻³) with M (mega, 10⁶) — letter case matters.
Real on-air practice: 0.5 μV = 500 nV = 0.0005 mV; mind the case of m vs M.
在法定计量单位中，词头M的数学意义和文字含义分别为：（“x＾m”表示“x的m次方”）
- A10＾6，兆
- B10＾(-6)，微
- C10＾3，千
- D10＾(-3)，毫
In the system of legal units of measurement, what are the mathematical significance and textual meaning of the prefix M? (‘x＾m’ denotes ‘x to the power of m’.)
- A10^6, mega (兆)
- B10^(-6), micro (微)
- C10^3, kilo (千)
- D10^(-3), milli (毫)
The SI prefix M (mega, 兆) represents a factor of 10^6. Option A correctly pairs the mathematical factor 10^6 with the Chinese character 兆. The other options describe micro (微, 10^-6), kilo (千, 10^3), and milli (毫, 10^-3), which are the prefixes μ, k, and m respectively.
US–China difference: The same SI prefixes (M, μ, G, n, T, p) are used in the US; 兆 = mega is standard internationally.
Common pitfall: Confusing the prefix letter M (mega, 10^6) with m (milli, 10^-3) — a case-sensitive error.
Real on-air practice: You routinely see MHz and kHz in band plans; 144 MHz = 144,000,000 Hz.
在法定计量单位中，词头μ的数学意义和文字含义分别为：（“x＾m”表示“x的m次方”）
- A10＾(-6)，微
- B10＾6，兆
- C10＾(-3)，毫
- D10＾3，千
In the system of legal units of measurement, what are the mathematical significance and textual meaning of the prefix μ? (‘x＾m’ denotes ‘x to the power of m’.)
- A10^(-6), micro (微)
- B10^6, mega (兆)
- C10^(-3), milli (毫)
- D10^3, kilo (千)
The prefix μ (micro, 微) represents 10^-6. Option A is correct. B is mega, C is milli, and D is kilo — all different prefixes.
US–China difference: Identical SI meaning in the US; μ is the Greek letter “mu”.
Common pitfall: Mixing μ (micro, 10^-6) with m (milli, 10^-3); note the lower-case Greek mu vs. the Latin m.
Real on-air practice: μV (microvolt) is the unit of receiver sensitivity you read on your S-meter specs.
在法定计量单位中，词头G的数学意义和文字含义分别为：（“x＾m”表示“x的m次方”）
- A10＾9，吉
- B10＾6，兆
- C10＾12，太
- D10＾(-12)，皮
In the system of legal units of measurement, what are the mathematical significance and textual meaning of the prefix G? (‘x＾m’ denotes ‘x to the power of m’.)
- A10^9, giga (吉)
- B10^6, mega (兆)
- C10^12, tera (太)
- D10^(-12), pico (皮)
The prefix G (giga, 吉) represents 10^9. Option A is correct. B (mega, 10^6), C (tera, 10^12), and D (pico, 10^-12) are different prefixes.
US–China difference: Same SI meaning; 吉 = giga in Chinese transliteration.
Common pitfall: Swapping G (giga, 10^9) with T (tera, 10^12) or M (mega, 10^6).
Real on-air practice: 2.4 GHz Wi-Fi/Bluetooth and 1.2 GHz amateur bands use the giga prefix.
在法定计量单位中，词头n的数学意义和文字含义分别为：（“x＾m”表示“x的m次方”）
- A10＾(-9)，纳
- B10＾9，吉
- C10＾12，太
- D10＾(-12)，皮
In the system of legal units of measurement, what are the mathematical significance and textual meaning of the prefix n? (‘x＾m’ denotes ‘x to the power of m’.)
- A10^(-9), nano (纳)
- B10^9, giga (吉)
- C10^12, tera (太)
- D10^(-12), pico (皮)
The prefix n (nano, 纳) represents 10^-9. Option A is correct. B is giga, C is tera, and D is pico — all different prefixes.
US–China difference: Same SI meaning; 纳 = nano.
Common pitfall: Confusing n (nano, 10^-9) with p (pico, 10^-12) or μ (micro, 10^-6).
Real on-air practice: Coaxial cable velocity factor and nanosecond timing appear in antenna phasing work.
在法定计量单位中，词头T的数学意义和文字含义分别为：（“x＾m”表示“x的m次方”）
- A10＾12，太
- B10＾-12，皮
- C10＾9，吉
- D10＾(-9)，纳
In the system of legal units of measurement, what are the mathematical significance and textual meaning of the prefix T? (‘x＾m’ denotes ‘x to the power of m’.)
- A10^12, tera (太)
- B10^-12, pico (皮)
- C10^9, giga (吉)
- D10^(-9), nano (纳)
The prefix T (tera, 太) represents 10^12. Option A is correct. B (pico, 10^-12), C (giga, 10^9), and D (nano, 10^-9) are all different prefixes.
US–China difference: Same SI meaning; 太 = tera.
Common pitfall: Swapping T (tera, 10^12) with G (giga, 10^9); also note option B uses the un-bracketed form 10＾-12.
Real on-air practice: Computer clock speeds and some RF synthesized ranges reach into the terahertz-order math.
在法定计量单位中，词头p的数学意义和文字含义分别为：（“x＾m”表示“x的m次方”）
- A10＾(-12)，皮
- B10＾12，太
- C10＾(-9)，纳
- D10＾9，吉
In the system of legal units of measurement, what are the mathematical significance and textual meaning of the prefix p? (‘x＾m’ denotes ‘x to the power of m’.)
- A10^(-12), pico (皮)
- B10^12, tera (太)
- C10^(-9), nano (纳)
- D10^9, giga (吉)
The prefix p (pico, 皮) represents 10^-12. Option A is correct. B (tera, 10^12), C (nano, 10^-9), and D (giga, 10^9) are different prefixes.
US–China difference: Same SI meaning; 皮 = pico.
Common pitfall: Confusing p (pico, 10^-12) with n (nano, 10^-9).
Real on-air practice: pF (picofarad) capacitor values are everywhere in RF tuning circuits.
以下哪个业余无线电通信缩语可以表述术语“射频”或特指无线电用途的某个频率？
- ARF
- BHF
- CAF
- DMF
Which of the following amateur radio abbreviations can express the term “radio frequency” or specifically refer to a certain frequency used for radio purposes?
- ARF
- BHF
- CAF
- DMF
RF (radio frequency, 射频) is the abbreviation that denotes radio frequency or a radio-used frequency. HF (high frequency), AF (audio frequency), and MF (medium frequency) are band/signal designations, not the general term for radio frequency itself.
US–China difference: RF is the universal English abbreviation used identically in the US.
Common pitfall: Picking HF (a band name) thinking it means “radio frequency”; HF ≠ RF.
Real on-air practice: You tune an “RF gain” control on the front panel — that is receiver radio-frequency gain.
术语“音频”是指人们可以普遍听到的声音的频率。以下描述正确的是：
- A音频的频率范围大致为16Hz-20kHz
- B音频位于VLF至MF多个频带内
- C音频的频率范围大致为16kHz-20kHz
- D音频位于VHF频带内
The term “audio frequency” (音频) refers to the frequency of sounds that people can generally hear. Which of the following descriptions is correct?
- AThe audio frequency range is approximately 16 Hz to 20 kHz
- BAudio frequencies lie within multiple bands from VLF to MF
- CThe audio frequency range is approximately 16 kHz to 20 kHz
- DAudio frequencies lie within the VHF band
音频 (audio frequency) is the range of sound audible to humans, approximately 16 Hz to 20 kHz (A). C gives a too-high and too-narrow range, and B/D wrongly place audio inside radio bands (VLF–MF, VHF) — audio is a baseband signal, not a radio-frequency band.
US–China difference: The 20 Hz–20 kHz audio range is the same international convention.
Common pitfall: Thinking audio frequencies are a radio band; they are baseband, below the RF used for transmission.
Real on-air practice: Your SSB voice occupies roughly 300 Hz–3 kHz of audio before modulation.
无线电通信及相关测试设备、电视设备和音频设备常用的传输接口标称阻抗分别为：
- A50欧、75欧和600欧
- B50欧、600欧和75欧
- C50欧、50欧和75欧
- D75欧、50欧和16欧
The commonly used nominal impedances of the transmission interfaces for radio communication and related test equipment, television equipment, and audio equipment are, respectively:
- A50 ohm, 75 ohm, and 600 ohm
- B50 ohm, 600 ohm, and 75 ohm
- C50 ohm, 50 ohm, and 75 ohm
- D75 ohm, 50 ohm, and 16 ohm
Radio/RF and test equipment commonly use a 50 ohm interface, television (coaxial) equipment uses 75 ohm, and audio (balanced line) equipment uses 600 ohm. Option A lists them in the correct order: 50 Ω, 75 Ω, 600 Ω.
US–China difference: Same standard impedances in the US (50 Ω RF, 75 Ω CATV, 600 Ω audio).
Common pitfall: Mixing up the order — 50 Ω is RF, 75 Ω is TV, 600 Ω is audio, not the reverse.
Real on-air practice: Your transceiver’s antenna port is 50 Ω; a 75 Ω TV feed line would be a mismatch.
1,805,000Hz可以表述为：
- A1.805MHz
- B1.805kHz
- C1.805mHz
- D1.805GHz
1,805,000 Hz can be expressed as:
- A1.805 MHz
- B1.805 kHz
- C1.805 mHz
- D1.805 GHz
1,805,000 Hz = 1.805 × 10^6 Hz = 1.805 MHz. Option A is correct. B (kHz) would be 1,000 times too small, C (mHz = 10^-3 Hz) is absurd, and D (GHz) is 1,000 times too large.
US–China difference: Same metric conversion; 1 MHz = 10^6 Hz everywhere.
Common pitfall: Misplacing the decimal — dividing/multiplying by 10^3 instead of 10^6.
Real on-air practice: 1.805 MHz is the lower edge of the 160 m band.
2430MHz可以表示为：
- A2.43GHz
- B243GHz
- C0.00243nHz
- D24.3kHz
2430 MHz can be expressed as:
- A2.43 GHz
- B243 GHz
- C0.00243 nHz
- D24.3 kHz
2430 MHz = 2.430 × 10^9 Hz = 2.43 GHz. Option A is correct. B (243 GHz) is 100× too large, C (nHz) is vanishingly small, and D (kHz) is 10^6× too small.
US–China difference: Identical conversion; 2.4 GHz is a globally recognized ISM band edge.
Common pitfall: Dividing by 10 (getting 243 GHz) instead of by 1000 when converting MHz to GHz.
Real on-air practice: 2.4 GHz is used by amateur ATV and some digital modes.
将阻值为1欧的电阻与13.8伏电源并联，电阻所耗散的功率大约为：
- A190瓦
- B13.8伏
- C13.8安
- D190伏安
A resistor of 1 ohm resistance is connected in parallel with a 13.8-volt power source; the power dissipated by the resistor is approximately:
- A190 W
- B13.8 V
- C13.8 A
- D190 VA
With the resistor directly across the 13.8 V source, P = V²/R = 13.8² / 1 ≈ 190.4 W, about 190 W (A). Options B and C give voltage and current (not power), and D (VA) is a volt-ampere figure inappropriate for a pure resistor.
US–China difference: Ohm’s law and the power formula P = V²/R are universal.
Common pitfall: Answering with volts or amps instead of watts; the question asks for power dissipated.
Real on-air practice: 13.8 V is the standard mobile/DC power for most ham transceivers.
5W可以表示为：
- A37dBm
- B5dBW
- C17dBm
- D35dBμ
5 W can be expressed as:
- A37 dBm
- B5 dBW
- C17 dBm
- D35 dBμ
5 W = 5000 mW. In dBm: 10·log10(5000) ≈ 36.99 ≈ 37 dBm (A). For reference, 5 W = 10·log10(5) ≈ 7 dBW (so B is wrong), 17 dBm = 50 mW, and 35 dBμ = 3.16 mW — none equal 5 W.
US–China difference: dBm/dBW are used identically in the US; 5 W is a common US VHF/UHF power limit.
Common pitfall: Confusing dBm (ref 1 mW) with dBW (ref 1 W); 5 W = 37 dBm = ~7 dBW.
Real on-air practice: Your 5 W handheld is 37 dBm — handy when comparing to a repeater’s sensitivity in dBm.
0.25W可以表示为：
- A54dBμ
- B6dBW
- C36dBm
- D25dBm
0.25 W can be expressed as:
- A54 dBμ
- B6 dBW
- C36 dBm
- D25 dBm
0.25 W = 250,000 μW. In dBμ (decibels relative to 1 μW): 10·log10(250000) ≈ 53.98 ≈ 54 dBμ (A). Note 0.25 W = 23.98 dBm (not 36 or 25 dBm) and 6 dBW = 4 W, so B/C/D are wrong. The exam uses dBμ here, not dBm.
US–China difference: US hams more often use dBm; the exam also tests dBμ (ref 1 μW).
Common pitfall: Auto-converting to dBm (≈24 dBm) and picking D (25 dBm) — but the marked unit is dBμ.
Real on-air practice: Field-strength and EIRP limits are sometimes given in dBμ, so know the 1 μW reference.
0.4kW可以表示为：
- A86dBμ
- B400dBm
- C6000dBm
- D34dBm
0.4 kW can be expressed as:
- A86 dBμ
- B400 dBm
- C6000 dBm
- D34 dBm
0.4 kW = 400 W = 400,000,000 μW. In dBμ: 10·log10(4×10^8) = 80 + 6.02 ≈ 86 dBμ (A). In dBm it would be 10·log10(400,000) ≈ 56 dBm, so B/C/D (400, 6000, 34 dBm) are all wrong magnitudes.
US–China difference: Same logarithmic conversion; the exam emphasizes the dBμ reference.
Common pitfall: Forgetting to convert kW→W→μW before taking the log; the answer is in dBμ not dBm.
Real on-air practice: High-power amplifier output (hundreds of watts) maps to ~80+ dBμ EIRP figures.
电源是业余无线电爱好者常用的一种供电装置。我们对电源的理解是：
- A电源是一种将某种形式的能量转化为电能的供电装置
- B电池是一种电源，其将化学能转化为电能，也称化学电源
- C直流电源是将输入交流电或直流电转换成电压和电流符合要求的另一直流电的装置
- D变压器可将交流电压和电流转换成交流的另一种电压和电流，可用来制作交流电源
A power source is a kind of power-supply device commonly used by amateur radio operators. Our understanding of a power source is: (Choose all that apply.)
- AA power source is a power-supply device that converts some form of energy into electrical energy
- BA battery is a power source that converts chemical energy into electrical energy, also called a chemical power source
- CA DC power source is a device that converts input AC or DC into another DC whose voltage and current meet the requirements
- DA transformer can convert AC voltage and current into another AC voltage and current, and can be used to make an AC power source
All four statements correctly describe a power source: it converts energy into electricity (A); a battery is a chemical source (B); a DC supply converts AC/DC into regulated DC (C); and a transformer reshapes AC to form an AC source (D). Each is a valid characterization of a power source.
US–China difference: Same basic definitions; US hams likewise use batteries, DC supplies, and transformers.
Common pitfall: Over-thinking and excluding a correct statement; here all four are true.
Real on-air practice: Your station runs on a 13.8 V DC supply converting mains AC — exactly option C.
电源两端电动势的方向为：
- A从电源的负极到正极
- B从电源的正极到负极
- C取决于负载电阻和电源内阻的相对大小
- D与电源的电压方向相同
The direction of the electromotive force (EMF, 电动势) across the two terminals of a power source is:
- Afrom the negative terminal to the positive terminal of the power source
- Bfrom the positive terminal to the negative terminal of the power source
- Cdepends on the relative magnitudes of the load resistance and the source internal resistance
- Dthe same as the direction of the source voltage
The electromotive force (电动势, EMF) of a source is defined as acting from the negative terminal toward the positive terminal inside the source (A). This is opposite to the external terminal voltage direction (B/D are wrong), and it is an intrinsic property, not dependent on load (C is wrong).
US–China difference: Same physics taught in US technician/General license theory.
Common pitfall: Reversing EMF direction with terminal-voltage direction; EMF points − to + inside the source.
Real on-air practice: Understanding EMF vs. terminal voltage explains why a loaded 13.8 V supply reads slightly low.
电源两端电压的方向为：
- A从电源的正极到负极
- B从电源的负极到正极
- C取决于负载电阻和电源内阻的相对大小
- D与电源的电动势方向相同
The direction of the voltage across the two terminals of a power source is:
- Afrom the positive terminal to the negative terminal of the power source
- Bfrom the negative terminal to the positive terminal of the power source
- Cdepends on the relative magnitudes of the load resistance and the source internal resistance
- Dthe same as the direction of the source EMF
The terminal voltage of a source drives current through the external circuit from the positive terminal to the negative terminal (A). This is the opposite direction to the internal EMF (so D is wrong), and is not load-dependent in direction (C wrong).
US–China difference: Identical convention; conventional current flows + to − outside the source.
Common pitfall: Confusing terminal-voltage direction with EMF direction (they are opposite).
Real on-air practice: Wiring your rig’s red lead to + and black to − follows this terminal-voltage polarity.
为业余无线电设备供电的外置电源具有多种类型。常见的有：
- A开关电源
- B线性电源
- C蓄电池
- D标准电池
External power sources for supplying amateur radio equipment come in several types. Common ones include: (Choose all that apply.)
- Aswitching power supply
- Blinear power supply
- Cstorage battery
- Dstandard cell
Common external power sources for amateur equipment are switching power supplies, linear power supplies, and storage batteries (A, B, C). A standard cell (标准电池, D) is a precision voltage reference, not a practical power source for equipment.
US–China difference: US hams use the same three; “standard cell” is a lab reference everywhere.
Common pitfall: Including a standard cell as a power source — it is only a voltage reference.
Real on-air practice: Field day runs on storage batteries; the shack uses a 13.8 V linear or switcher.
下列哪一种电池可以充电？
- A锂离子电池
- B钠离子电池
- C铅酸电池
- D碱性干电池
Which of the following batteries can be recharged? (Choose all that apply.)
- Alithium-ion battery
- Bsodium-ion battery
- Clead-acid battery
- Dalkaline dry cell
Lithium-ion, sodium-ion, and lead-acid batteries are all secondary (rechargeable) cells (A, B, C). An alkaline dry cell (碱性干电池, D) is a primary (non-rechargeable) battery and should not be recharged.
US–China difference: Same battery chemistry classifications apply in the US.
Common pitfall: Thinking alkaline dry cells are rechargeable — attempting to recharge them is unsafe.
Real on-air practice: Your handheld’s Li-ion pack and your go-kit’s lead-acid are both rechargeable.
如何在电网停电的情况下给一个12伏的铅酸蓄电池充电？
- A用适当的连线将待充电蓄电池与汽车的蓄电池并联，然后发动车辆
- B往蓄电池里加一些酸
- C将蓄电池放在冰里冷却一会儿
- D将蓄电池串联一个电灯泡作为限流装置，然后连接到220伏市电上
How can a 12-volt lead-acid battery be charged when the mains power is out?
- AConnect the battery to be charged in parallel with a car’s battery using appropriate cables, then start the vehicle
- BAdd some acid to the battery
- CPut the battery in ice to cool it for a while
- DConnect the battery in series with a light bulb as a current limiter, then connect it to 220 V mains
The safe method is to parallel the discharged 12 V battery with a running car’s battery/alternator so the running engine’s charging system tops it up (A). Adding acid (B), cooling it (C), or connecting directly to 220 V mains (D) are incorrect and dangerous.
US–China difference: A “boost” from a car battery is common practice in the US too; never connect to mains.
Common pitfall: Imagining you can charge a battery from 220 V AC directly — that destroys it and is a shock hazard.
Real on-air practice: Field-day operators often recharge from a vehicle’s 12 V system via jumper cables.
使用蓄电池为电台供电时，应如何估算电池供电的时长？
- A用电池的标称安时数除以收发信机的平均工作电流
- B用电池的标称瓦时数除以收发信机的发射功率
- C用电池的标称电压除以收发信机的平均工作电流
- D用收发信机的发射功率除以电池的标称电压
When using a storage battery to power a radio station, how should the battery operating time be estimated?
- ADivide the battery’s nominal ampere-hour rating by the transceiver’s average operating current
- BDivide the battery’s nominal watt-hour rating by the transceiver’s transmit power
- CDivide the battery’s nominal voltage by the transceiver’s average operating current
- DDivide the transceiver’s transmit power by the battery’s nominal voltage
Operating time (hours) ≈ capacity (Ah) ÷ average current (A). Using the battery’s nominal ampere-hour (安时) rating divided by the transceiver’s average operating current gives the runtime (A). Watt-hours ÷ transmit-only power (B) ignores receive/standby current and is not the standard estimate; C/D are dimensionally wrong.
US–China difference: The Ah ÷ average-current rule is universal; US hams use it for Field Day planning.
Common pitfall: Dividing by transmit power only, forgetting receive/standby draw dominates much of the time.
Real on-air practice: A 20 Ah battery at 2 A average draw ≈ 10 hours of portable operation.
电源的内阻对电路的影响是：
- A使电源的实际输出电压降低
- B使电源的电动势降低
- C使电源的输出功率增加
- D使电源的自身的能耗降低
The effect of a power source’s internal resistance on a circuit is:
- AIt reduces the source’s actual output voltage
- BIt reduces the source’s EMF
- CIt increases the source’s output power
- DIt reduces the source’s own energy consumption
Internal resistance causes a voltage drop (I·r) inside the source, so the terminal (output) voltage V = E − I·r falls as load current rises (A). The EMF (E) itself is unaffected (B wrong), and output power is not increased (C wrong).
US–China difference: Same internal-resistance model taught in US license theory.
Common pitfall: Thinking internal resistance lowers the EMF; it only lowers the terminal voltage under load.
Real on-air practice: Keying PTT on a weak battery drops the voltage — the classic internal-resistance symptom.
有些收发信机会在直流13.8V供电线路中串联一个熔断器，并在其后反向并联一个额定电流很大的二极管作保护之用。该电路利用了二极管的什么特性？是如何工作的？
- A利用二极管中PN结的单向导电性；若电源极性接反，近乎短路的电流烧断熔丝，切断供电
- B在电源过压时利用二极管的击穿特性吸收电流以稳定供电电压
- C在电源过流时利用二极管的击穿特性吸收电流以稳定供电电压
- D若设备过热时利用二极管的热失控特性短路电源，烧断熔丝，切断供电
Some transceivers have a fuse in series in the 13.8 V DC supply line, followed by a diode of very high rated current connected in anti-parallel for protection. What characteristic of the diode does this circuit exploit, and how does it work?
- AIt exploits the unidirectional conductivity of the PN junction in the diode; if the supply polarity is reversed, a near-short-circuit current blows the fuse and cuts off the power
- BUnder overvoltage it uses the diode’s breakdown characteristic to absorb current and stabilize the supply voltage
- CUnder overcurrent it uses the diode’s breakdown characteristic to absorb current and stabilize the supply voltage
- DIf the equipment overheats, it uses the diode’s thermal-runaway characteristic to short the supply and blow the fuse, cutting off power
The reverse-parallel (anti-parallel) diode is a polarity-protection device. Normally it is reverse-biased and conducts nothing. If the 13.8 V supply is connected backwards, the diode becomes forward-biased and, with its very high current rating, effectively shorts the line, so the series fuse blows and disconnects the wrong-polarity voltage (A). Options B/C describe zener-like voltage clamping (not this circuit), and D describes thermal runaway (incorrect).
US–China difference: Reverse-polarity protection diodes/fuses are standard on US rigs too.
Common pitfall: Confusing this with overvoltage (zener) protection; here the diode handles reversed polarity, not spikes.
Real on-air practice: Hooking a power lead backward is a classic mistake this circuit is designed to survive.
有些收发信机会在13.8V直流电源插座附近安装一个标有数字的复位按钮。其作用是什么？
- A当设备过流时切断电源
- B当电源极性接反时切断电源
- C如果工作温度超过数字所注的温度值则切断电源
- D如果工作电压超过数字所注的伏特数则切断电源
Some transceivers have a reset button marked with a number near the 13.8 V DC power socket. What is its function? (Choose all that apply.)
- AIt cuts off power when the equipment is overcurrent
- BIt cuts off power when the supply polarity is reversed
- CIf the operating temperature exceeds the temperature value marked by the number, it cuts off power
- DIf the operating voltage exceeds the volt value marked by the number, it cuts off power
This reset button is the protective device that trips and disconnects the supply on overcurrent (A) and on reversed polarity (B); once the fault clears you press it to reset. It is not a temperature (C) or overvoltage (D) setpoint — those would be labeled differently.
US–China difference: US transceivers use inline resetting breakers/polyswitches for the same overcurrent/reverse-polarity roles.
Common pitfall: Assuming the number is a temperature or voltage threshold; it marks the current rating of the resettable protector.
Real on-air practice: A shorted power plug trips this; you fix the wiring and press the button to resume.
万用表可以用来测量哪些物理量？
- A电压、电流和电阻
- B信号的强度和噪声
- C阻抗中的电抗成分
- D驻波比和射频功率
Which physical quantities can a multimeter be used to measure?
- Avoltage, current, and resistance
- Bsignal strength and noise
- Cthe reactive (imaginary) component of impedance
- Dstanding-wave ratio (SWR) and RF power
A basic multimeter directly measures the three fundamental electrical quantities — voltage, current, and resistance (电压、电流和电阻) — using its DC/AC voltage, current, and resistance ranges. Signal strength/noise (B), the reactive part of impedance (C), and SWR/RF power (D) require specialized instruments such as a spectrum analyzer, an impedance bridge, or an SWR/RF power meter.
US–China difference: Same DMM basics in the US; US exams also stress that a DMM does not directly measure SWR or RF power.
Common pitfall: Assuming the ohms range measures the reactive part of impedance — it only reads DC resistance.
Real on-air practice: You grab a DMM to check a 13.8 V supply or a blown fuse, not to tune an antenna.
用万用表的交流电压档测量简单正弦交流电压时所得的读数为该电压的：
- A有效值
- B最大值
- C峰-峰值
- D平均值
For a simple sinusoidal AC voltage measured with a multimeter’s AC voltage range, the reading is the ___ of that voltage:
- ARMS (effective) value
- Bpeak (maximum) value
- Cpeak-to-peak value
- Daverage value
On the AC voltage range a multimeter reads the RMS (有效值) value of a sine wave. The peak (最大值) is larger by √2 (about 1.414) and the peak-to-peak (峰-峰值) by 2√2, so options B and C are too large; the full-cycle average (D) of a sine is zero.
US–China difference: Same RMS convention in the US.
Common pitfall: Confusing RMS with peak or peak-to-peak on a sine wave.
Real on-air practice: When you read 120 V AC on the wall, that figure is RMS.
用万用表的直流电压档测量简单正弦交流电压时所得的读数均应视为：
- A零值
- B该电压的最大值
- C该电压的峰-峰值
- D该电压的有效值
For a simple sinusoidal AC voltage measured with a multimeter’s DC voltage range, the reading should be regarded as:
- Azero
- Bthe peak value of that voltage
- Cthe peak-to-peak value of that voltage
- Dthe RMS value of that voltage
A DC voltage range is not designed for AC; a pure sine wave has equal positive and negative areas, so its average (what the DC range integrates) is essentially zero. Only a true-RMS meter on the AC range reads the RMS value; the DC range does not give the peak (B), peak-to-peak (C), or RMS (D).
US–China difference: Same physics; the US also warns against using the DC range on AC.
Common pitfall: Thinking the DC range gives the RMS of an AC signal.
Real on-air practice: Measuring 120 V AC on the DC scale shows ~0 — a sign you are on the wrong range.
使用万用表测量电流时，应怎样将仪表接入电路？
- A串联至电路中
- B并联至电路中
- C正交至电路中
- D与电路同相连接
When using a multimeter to measure current, how should the meter be connected into the circuit?
- Ain series with the circuit
- Bin parallel with the circuit
- Cconnected orthogonally (at a right angle) to the circuit
- Dconnected in phase with the circuit
An ammeter must be placed in series so the full load current flows through it (串联). A voltmeter is connected in parallel. Options C and D are meaningless connection descriptions for current measurement.
US–China difference: Identical in US practice.
Common pitfall: Putting the meter in parallel on the current range creates a near-short and blows the internal fuse.
Real on-air practice: You break the circuit and insert the DMM in series to read the current draw of a rig.
下列哪一种做法可能损坏万用表？
- A用万用表的电流档测量电压
- B用数字式万用表的电阻档测量电压
- C用大电压量程测量了一个非常小的电压
- D没有让待测量设备适当地预热
Which of the following practices may damage a multimeter?
- Ameasuring voltage with the multimeter’s current range
- Bmeasuring voltage with a digital multimeter’s resistance range
- Cmeasuring a very small voltage with a large voltage range
- Dfailing to let the device under test warm up adequately
Using the current (amps) range across a voltage source shorts the source through the meter’s tiny shunt resistor, blowing the fuse or destroying the meter — the classic damage case (A). A large range on a small voltage (C) only loses resolution; B and D are not damaging.
US–China difference: US DMMs likewise blow the internal fuse if you measure volts on the amps jack.
Common pitfall: Forgetting to move the lead/range from amps to volts before touching a voltage source.
Real on-air practice: Many hams keep a spare fuse because they once measured 13.8 V on the 10 A jack.
用万用表的电阻档测量某电路两点间的阻值时需要留意什么先决条件？
- A确保待测电路没有连接任何电源
- B确保待测电路已正常接通了工作所需的电源
- C确保待测电路已经正常接地
- D确保待测电路正常工作在所需频率下
When measuring the resistance between two points of a circuit with a multimeter’s resistance range, what precondition must be noted?
- Aensure the circuit under test is not connected to any power source
- Bensure the circuit under test is properly powered with its operating supply
- Censure the circuit under test is properly grounded
- Densure the circuit under test is operating normally at the required frequency
Resistance measurement uses the meter’s own internal current source, so the circuit under test must be de-energized; otherwise you get wrong readings or damage the meter. Option A is the required precondition; B is wrong (powered), and C/D are irrelevant.
US–China difference: Same rule worldwide.
Common pitfall: Measuring ohms on a powered circuit.
Real on-air practice: Power down and disconnect before checking a coil or a PCB trace.
要大致判断一节干电池是否已经失效，可用的方法是：
- A用万用表的电压档测量电池的端电压，显著低于标称电压表明电池失效
- B用指针式万用表的电阻档测量电池的内阻。指针缓慢回退表明电池失效
- C找一支内置熔丝的万用表，用电流档测量电池两端并观察电流是否够大
- D用万用表的通断测试档判断电池极性。如果极性消失则表明电池已失效
A method that can be used to roughly judge whether a dry-cell battery has failed is:
- Ameasure the battery’s terminal voltage with the multimeter’s voltage range; a value significantly below the nominal voltage indicates the battery has failed
- Bmeasure the battery’s internal resistance with an analog multimeter’s resistance range; the pointer slowly returning indicates failure
- Cfind a multimeter with a built-in fuse, measure the battery terminals with the current range, and observe whether the current is large enough
- Duse the multimeter’s continuity-test range to judge battery polarity; if the polarity disappears the battery has failed
A simple go/no-go test is to measure the no-load terminal voltage; a healthy cell reads near its nominal voltage, while a failed one reads much lower (A). B’s needle method is unreliable, C risks a large short-circuit current through the meter, and D is nonsense (polarity cannot “disappear”).
US–China difference: US hams do the same quick voltage check.
Common pitfall: Believing polarity can “disappear” or using a current short test.
Real on-air practice: A 1.2 V NiMH reading 0.9 V under test is weak.
用万用表的电阻档测量一副阻抗为50欧姆的四分之一波长接地天线，读数为0欧。可能的情况是：
- A该天线与地之间可能存在由电感线圈构成的直流通路
- B该天线肯定已经短路损坏
- C该天线肯定无法与特性阻抗为50欧的馈线相匹配
- D该天线肯定无法与输出阻抗为50欧姆的收发信机相匹配
Using a multimeter’s resistance range to measure a quarter-wavelength grounded antenna with an impedance of 50 ohms gives a reading of 0 ohms. A possible situation is:
- Athere may be a DC path between the antenna and ground formed by an inductor coil
- Bthe antenna must already be short-circuited/damaged
- Cthe antenna certainly cannot be matched to a feed line with 50-ohm characteristic impedance
- Dthe antenna certainly cannot be matched to a transceiver with 50-ohm output impedance
A quarter-wave grounded antenna behaves as a DC short only if there is a DC path to ground — here, plausibly via a loading/inductor coil that is DC-continuous. So 0 Ω suggests such a DC path may exist (A). It does not prove the antenna is damaged (B) or mismatched (C/D); those need RF measurements.
US–China difference: Same antenna DC-resistance reasoning in the US.
Common pitfall: Inferring a shorted antenna from a 0 Ω DC reading on a grounded 1/4-wave.
Real on-air practice: A DC continuity check cannot tell you whether the antenna actually radiates.
用万用表的电阻档测量一副阻抗为50欧姆的四分之一波长接地天线，读数为无穷大。可能的情况是：
- A该天线与地之间不存在由电感线圈构成的直流通路
- B该天线肯定已经开路损坏
- C该天线肯定无法与特性阻抗为50欧的馈线相匹配
- D该天线肯定无法与输出阻抗为50欧姆的收发信机相匹配
Using a multimeter’s resistance range to measure a quarter-wavelength grounded antenna with an impedance of 50 ohms gives a reading of infinity. A possible situation is:
- Athere is no DC path between the antenna and ground formed by an inductor coil
- Bthe antenna must already be open-circuited/damaged
- Cthe antenna certainly cannot be matched to a feed line with 50-ohm characteristic impedance
- Dthe antenna certainly cannot be matched to a transceiver with 50-ohm output impedance
An infinite reading means no DC path to ground exists (no inductor shunt), so A is the correct inference. It does not prove the antenna is open-damaged (B) or mismatched (C/D); those require RF testing.
US–China difference: Same concept.
Common pitfall: Assuming an infinite-ohm reading means the antenna is broken.
Real on-air practice: DC resistance alone does not certify RF performance.
用万用表的电阻档测量一副用四分之一波长的导线自制的偶极天线的中心馈电点阻抗。可能的情况是：
- A读数为无穷大
- B读数为50欧姆
- C随着天线升高，阻抗逐渐接近75欧姆
- D读数受表笔连线引入的附加驻波比影响
Using a multimeter’s resistance range to measure the center-feed-point impedance of a home-built quarter-wavelength-wire dipole antenna. A possible situation is:
- Athe reading is infinity
- Bthe reading is 50 ohms
- Cas the antenna is raised, the impedance gradually approaches 75 ohms
- Dthe reading is affected by the additional SWR introduced by the test-lead wiring
A center-fed dipole is balanced: its two halves are separated by the feed-point insulator, so there is no DC path between them and the DC resistance reads infinity (A). The 50 Ω (B) is the RF feed-point impedance at resonance, not a DC reading; C/D are irrelevant to a DC ohmmeter.
US–China difference: Same concept; a US dipole DC check also reads open.
Common pitfall: Expecting a DC ohmmeter to show the 50/75 Ω feed impedance.
Real on-air practice: Your dipole’s center insulator guarantees an open DC reading.
用万用表的电阻档测量一条终端开路的任意长度理想50欧同轴电缆的中心导体和屏蔽层之间的电阻。可能的情况是：
- A读数为无穷大
- B读数为0欧姆
- C读数为50欧姆
- D读数与电缆长度有关
Using a multimeter’s resistance range to measure the resistance between the center conductor and the shield of an ideal 50-ohm coaxial cable of arbitrary length with an open-circuited (terminated open) end. A possible situation is:
- Athe reading is infinity
- Bthe reading is 0 ohms
- Cthe reading is 50 ohms
- Dthe reading depends on the cable length
Open-circuited coax has its center conductor and shield disconnected at both ends, so the DC resistance is infinite (A). The 50 Ω is the RF characteristic impedance, not a DC measurement, and for an ideal open line it does not depend on length (so C/D are wrong).
US–China difference: Same worldwide.
Common pitfall: Reading “50 Ω” on the ohms range of open coax.
Real on-air practice: You use an ohmmeter to find a short in a feed line, not its characteristic impedance.
用万用表的电阻档测量一条终端短路的任意长度理想50欧同轴电缆的中心导体和屏蔽层之间的电阻。可能的情况是：
- A读数为0欧姆
- B读数为无穷大
- C读数为50欧姆
- D读数与电缆长度有关
Using a multimeter’s resistance range to measure the resistance between the center conductor and the shield of an ideal 50-ohm coaxial cable of arbitrary length with a short-circuited end. A possible situation is:
- Athe reading is 0 ohms
- Bthe reading is infinity
- Cthe reading is 50 ohms
- Dthe reading depends on the cable length
A shorted end ties the center conductor to the shield, so the DC resistance is 0 Ω (A). The 50 Ω characteristic impedance is an RF property; an ideal short reads 0 Ω regardless of length, so C/D are wrong.
US–China difference: Same.
Common pitfall: Expecting 50 Ω on a DC shorted-coax test.
Real on-air practice: A 0 Ω reading across the connector means the far end is shorted.
哪一种焊接材料比较适合业余无线电制作和维修？
- A松香芯焊锡丝
- B银焊条
- C铜焊条
- D酸性芯焊锡丝
Which soldering material is relatively suitable for amateur radio construction and repair?
- Arosin-core solder wire
- Bsilver brazing rod
- Ccopper welding rod
- Dacid-core solder wire
Rosin-core solder is standard for electronics: the rosin flux cleans the joint without being corrosive. Acid-core solder (D) is for plumbing and attacks electronics; silver/copper brazing rods (B/C) are for metal joining, not PCB soldering. So A is correct.
US–China difference: US electronics also use rosin/no-clean flux; acid-core is forbidden on boards.
Common pitfall: Using acid-core solder on radio gear.
Real on-air practice: Keep rosin-core 60/40 or lead-free solder for building a kit.
💬 Have questions about this topic, or FCC / CRAC exam preparation?
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本手册仅供业余无线电爱好者学习交流，题库原题版权归 CRAC（中国无线电协会业余无线电分会）所有，英文翻译由 BG7BAG 编译，转载请注明出处。
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