CRAC Class B (2025) — Questions 951–960
U1026. For a triangular-wave signal with a minimum of 0 V and a peak-to-peak of 100 V, its average value is:
对于最小值为0伏、峰-峰值为100伏的三角波信号，其平均值 电压为：
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A 0-to-100 V triangle (50% duty) has an average of 50.0 V (half the peak). Option A is correct. B is peak, C is the sine RMS factor.
U1027. Drive two identical resistive loads with a 120 V battery bank and an AC transformer of 120 V peak voltage respectively. Over the same time, which resistor emits more heat?
用电压为120V的蓄电池组和峰值电压为120V的交流变压器分 别驱动参数相同的两个电阻负载。在相同时间内，哪一个电阻 发出的热量多？
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The battery supplies 120 V DC → power = 120²/R. The AC transformer's peak is 120 V, so its RMS = 120/√2 ≈ 84.9 V → power = 84.9²/R = 7200/R. The ratio 14400/7200 = 2, so the battery-driven resistor emits about twice the heat. Option A is correct.
U1028. Drive two identical resistive loads with a 120 V battery bank and an AC transformer of 120 V RMS voltage respectively. Over the same time, which resistor emits more heat?
用电压为120V的蓄电池组和有效值电压为120V的交流变压器 分别驱动参数相同的两个电阻负载。在相同时间内，哪一个电 阻发出的热量多？
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Both sources are 120 V RMS equivalent (the battery's 120 V DC and the transformer's 120 V RMS give the same effective voltage), so each resistor dissipates the same power and emits the same heat. Option A is correct.
U1029. Drive two identical resistive loads with a 120 V battery bank and a 120 V RMS AC transformer with a series diode respectively (ignore the diode forward drop). Over the same time, which resistor emits more heat?
用电压为120V的蓄电池组和有效值电压为120V的交流变压器 串联二极管后分别驱动参数相同的两个电阻负载。在相同时间 内，哪一个电阻发出的热量多？（忽略二极管的正向压降）
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The battery gives 120 V DC. The AC (120 V RMS, peak ≈ 169.7 V) through a series diode is half-wave rectified; the load sees only the positive halves, with RMS = Vpk/2 ≈ 84.9 V. Power ratio = (120²)/(84.9²) = 2, so the battery-driven resistor is about twice as hot. Option A is correct.
U1030. Drive two identical resistive loads with a 120 V battery bank and a 120 V peak AC transformer through a capacitor-filtered full-wave rectifier respectively (ignore the rectifier forward drop). Over the same time, which resistor emits more heat?
用电压为120V的蓄电池组和峰值电压为120V的交流变压器经 过带电容滤波的全波整流电路分别驱动参数相同的两个电阻负 载。在相同时间内，哪一个电阻发出的热量多？（忽略整流器 的正向压降）
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A capacitor-filtered full-wave rectifier charges to near the AC peak (≈120 V, ignoring drop), which equals the 120 V battery DC. Thus both resistors see ~120 V and dissipate roughly the same power. Option A is correct.
U1031. Drive two identical resistive loads with a 120 V RMS, 50 Hz AC source and a 120 V RMS, 10 kHz square-wave source respectively. Over the same time, which resistor emits more heat?
用有效值电压为120V、频率为50Hz的交流电源和有效值电压 为120V、频率为10kHz的方波电源分别驱动参数相同的两个电 阻负载。在相同时间内，哪一个电阻发出的热量多？
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A pure resistor's heating depends only on the RMS voltage, not on frequency. Both sources are 120 V RMS, so both resistors dissipate the same power and emit the same heat. Option A is correct. 电路元件与符号 Circuit Components and Symbols
U1032. The circuit-component symbol in the accompanying figure represents:
附图中的电路元器件符号代表：
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The symbol shown in the figure (see [F]LK0497.jpg) is the standard ground (接地) symbol — the horizontal lines decreasing in width. Antenna, resistor, and diode have different schematic symbols, so only A is correct.
U1033. By manufacturing material, common resistors include: (Choose all that apply.)
按制造材料细分，常见的电阻有：
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Classified by material, common resistors are carbon-film (碳膜), metal-film (金属膜), and wirewound (线绕) — options A, B, C. A damping resistor (D) is a function-specific type, not a material category, so it is not a correct "by material" answer.
U1034. Among components used in assembling an amateur transceiver, the one that is usually marked with a rated dissipation power is:
在组装业余收发信机所用的元器件中，标有额定耗散功率的通 常是：
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Wirewound resistors are explicitly marked with a rated dissipation (power) because they are built to handle high power. Film capacitors, transistors, and ICs are marked mainly with voltage/current/other ratings, not a power-watt figure as prominently. Option A is correct.
U1035. A resistor's "rated power" means:
电阻的“额定功率”是指：
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The rated power (额定功率) is the maximum power the resistor can dissipate continuously in normal service without damage; the actual dissipated power depends on the circuit. Option A is correct; B/C/D misstate it as a minimum, a fixed consumption, or a supplied power.