In electrical engineering, impedance is the opposition to alternating current presented by the combined effect of resistance and reactance in a circuit.
The self resonant frequency of an inductor is the frequency at which the parasitic capacitance of the inductor resonates with the ideal inductance of the inductor resulting in an extremely high impedance. At this frequency the device looks like an open circuit.
The outer diameter (OD) of a hollow circular pipe is the measurement of the outside edges of the pipe passing through its center.