CRAC Class C (2025) — Questions 901–910
U1024. For a square-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伏的方波信号，其平均值电 压为：
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A 0-to-100 V square wave (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.
U1025. For a triangular-wave signal with a minimum of -50 V and a peak-to-peak of 100 V, its average value is:
对于最小值为-50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 symmetric triangular wave (-50 V to +50 V) has equal positive and negative area, so its average over a full cycle is 0 V. Option A is correct.
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.
U1155. The component capable of storing energy in the form of an electric field is:
能够以电场形式储存能量的元件是：
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A 电容 (capacitor) stores energy in an electric field between its plates. A resistor dissipates energy as heat; an inductor stores energy in a magnetic field; a varistor is a voltage-dependent nonlinear resistor. Only the capacitor stores energy electrostatically.
U1156. If a sinusoidal AC voltage is applied across a capacitor, the magnitude of the current flowing through the capacitor:
若在电容器的两端施加一个正弦交流电压，则流过电容器的电 流的大小：
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For a capacitor the current is I = V·ω·C = V·2πf·C, where V is the applied voltage and C is the capacitance. Thus the current magnitude is directly proportional to both the voltage and the capacitance, so A is correct and B/C/D are wrong.