Key Terms
- ac current
- current that fluctuates sinusoidally with time at a fixed frequency
- ac voltage
- voltage that fluctuates sinusoidally with time at a fixed frequency
- alternating current (ac)
- flow of electric charge that periodically reverses direction
- average power
- time average of the instantaneous power over one cycle
- bandwidth
- range of angular frequencies over which the average power is greater than one-half the maximum value of the average power
- capacitive reactance
- opposition of a capacitor to a change in current
- direct current (dc)
- flow of electric charge in only one direction
- impedance
- ac analog to resistance in a dc circuit, which measures the combined effect of resistance, capacitive reactance, and inductive reactance
- inductive reactance
- opposition of an inductor to a change in current
- phase angle
- amount by which the voltage and current are out of phase with each other in a circuit
- power factor
- amount by which the power delivered in the circuit is less than the theoretical maximum of the circuit due to voltage and current being out of phase
- quality factor
- dimensionless quantity that describes the sharpness of the peak of the bandwidth; a high quality factor is a sharp or narrow resonance peak
- resonant frequency
- frequency at which the amplitude of the current is a maximum and the circuit would oscillate if not driven by a voltage source
- rms current
- root mean square of the current
- rms voltage
- root mean square of the voltage
- step-down transformer
- transformer that decreases voltage and increases current
- step-up transformer
- transformer that increases voltage and decreases current
- transformer
- device that transforms voltages from one value to another using induction
- transformer equation
- equation showing that the ratio of the secondary to primary voltages in a transformer equals the ratio of the number of turns in their windings