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AC power and power factor

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Objective

Measure the RMS voltage and current, real power and power factor of an R–L load on 50 Hz mains-style supply.

Procedure

  1. Run and compare the voltage and current waveforms: the current lags.
  2. Change L to 0: the power factor becomes 1.

Theory

|Z| = √(R² + (ωL)²) = 137.4 Ω, I_rms = V_rms/|Z| = 51.5 mA, P = I²R, PF = cos φ = R/|Z| = 0.728 (lagging).

Questions to answer

  1. Why do utilities charge for reactive power?

Components used

Function generator (sine), Inductor 100uH, Oscilloscope (2-channel), Resistor 220 ohm 1/4W

About the model

Ideal wires; component models as listed in the catalogue (no parasitics, no temperature drift). Built without a breadboard so the schematic stays readable.

Open this experiment in the circuit simulator

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