Direct current (DC) circuits involve current flowing in one
direction. In alternating current (AC) circuits, instead of a constant
voltage supplied by a battery, the voltage oscillates in a sine wave
pattern, varying with time as:
V = Vo sin wt
In a household circuit, the frequency is 60 Hz. The angular frequency is related to the frequency, f, by:
w = 2πf
Vo represents the maximum voltage, which in a household circuit in North America is about 170 volts. We talk of a household voltage of 120 volts, though; this number is a kind of average value of the voltage. The particular averaging method used is something called root mean square (square the voltage to make everything positive, find the average, take the square root), or rms. Voltages and currents for AC circuits are generally expressed as rms values. For a sine wave, the relationship between the peak and the rms average is:
rms value = 0.707 peak value
V = Vo sin wt
In a household circuit, the frequency is 60 Hz. The angular frequency is related to the frequency, f, by:
w = 2πf
Vo represents the maximum voltage, which in a household circuit in North America is about 170 volts. We talk of a household voltage of 120 volts, though; this number is a kind of average value of the voltage. The particular averaging method used is something called root mean square (square the voltage to make everything positive, find the average, take the square root), or rms. Voltages and currents for AC circuits are generally expressed as rms values. For a sine wave, the relationship between the peak and the rms average is:
rms value = 0.707 peak value
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