What does E(inst) represent?

• A. The frequency
• B. The peak-to-peak voltage
• C. The instantaneous voltage at any point on the waveform
• D. The average voltage

Answer: (C)

E(inst) is the voltage value at a specific moment in time on the waveform. It represents the instantaneous, momentary voltage, often written as e(t) or v(t). This is different from frequency, which tells you how often the waveform repeats per second; different from peak-to-peak voltage, which is the total swing from the maximum to the minimum; and different from average voltage, which is the mean value over time. For a sine wave, E(inst) changes with time according to Vm sin(ωt), so at any given moment it has a single voltage value, positive or negative, reflecting the waveform’s position at that instant.