Why are copper oxide rectifiers, associated...

Why are copper oxide rectifiers, associated...

Question 1 of 27070P94odTRj7wkHQ2SCnR2t

Why are copper oxide rectifiers, associated with DC voltmeters to measure AC, unsuitable for the measurement of voltages at radio frequencies?

Question 1 of 27070

Q

Why are copper oxide rectifiers, associated with DC voltmeters to measure AC, unsuitable for the measurement of voltages at radio frequencies?

🔍 Key Concepts

• Copper oxide rectifier behavior at different frequencies (low frequency vs radio frequency) • Effect of shunt (parallel) capacitance on AC measurements, especially at high frequencies • How unintended capacitance can form a bypass path for RF signals, affecting meter readings

💭 Think About

• At radio frequencies, how does even a small capacitance affect impedance and current flow compared with at power-line frequencies (50/60 Hz)? • If a rectifier has a certain shunt capacitance, will that capacitance tend to short-circuit or pass more of the RF signal around the meter movement? • Which option correctly describes the size of the shunt capacitance that would most disturb RF voltage measurements?

✅ Before You Answer

• Compare the reactance of a capacitor at low frequency vs high (radio) frequency: $X_C = \tfrac{1}{2\pi f C}$ . What happens as frequency increases? • Decide whether a large or small shunt capacitance would give more bypassing effect at RF and therefore make the reading unreliable. • Check which choices are mutually exclusive (cannot both be true at once), especially regarding "low" vs "large" shunt capacitance.