AC Circuits & Measurements

AC Circuits:- An AC (Alternating Current) circuit is an electrical circuit in which the current and voltage change their magnitude and direction periodically with time, usually following a sinusoidal waveform.

• Main Components of AC Circuits
  • Resistance (R):- Opposes the flow of current. In a pure resistive circuit, current and voltage are in the same phase.
  • Inductance (L):- Opposes change in current due to magnetic field. Current lags behind voltage.
  • Capacitance (C):- Stores energy in an electric field. Current leads the voltage.
• Important Terms in AC Circuits
  • RMS Value: Effective value of AC that produces the same heating effect as DC.
  • Frequency (Hz): Number of cycles per second (50 Hz in India).
  • Reactance (XL, XC): Opposition offered by inductance and capacitance.
  • Impedance (Z): Total opposition in AC circuit (combination of R, L, and C).
  • Power Factor (cosφ): Ratio of real power to apparent power; indicates efficiency.

AC Measurements:- AC measurements are used to determine electrical quantities accurately in AC systems.

• Common Measuring Instruments
  • AC Ammeter: Measures alternating current.
  • AC Voltmeter: Measures alternating voltage.
  • Wattmeter: Measures real (active) power.
  • Energy Meter: Measures electrical energy consumed (kWh).
  • Frequency Meter: Measures supply frequency.
  • Power Factor Meter: Measures power factor (cosφ).
• Power in AC Circuits
  • Active Power (P): Useful power (Watts).
  • Reactive Power (Q): Power stored and returned by inductors and capacitors (VAR).
  • Apparent Power (S): Combination of active and reactive power (VA).