I - Symbol used to designate current. See current.
I.D. - Abbreviation for inside diameter.
IAIACS - Abbreviation for International Annealed Copper Standard. Refined copper for electrical conductors: 100% conductivity at 20° C for 1 m X 1 mm2 has 1/58 ohm resistivity, 8.93 (changed to 8.89 in 1977) grams per mm2 density, 0.000017 per degree C coefficient of linear expansion, and 1/254.45 per degree C coefficient of variation of resistance.
IC - Abbreviation for integrated circuit.
ICEA - Abbreviation for Insulated Cable Engineers Association, formerly IPCEA.
ID - Abbreviation for identification.
IEC - Abbreviation for International Electrotechnical
Commission, similar to the International Standards Organization (ISO).
IEEE - Abbreviation for Institute of Electrical and Electronic Engineers. Formerly American Institute of Electrical Engineers (AIEE) and Institute of Radio Engineers (IRE).
IMP - Abbreviation for impedance. See impedance.
IMPACT STRENGTH - A test for determining the mechanical punishment a cable can withstand without physical or electrical breakdown by impacting with a given weight, dropped a given distance, in a controlled environment.
IMPEDANCE - A measure of the response of an electric circuit to an alternating current. Measured in ohms (volts per ampere). Symbol Z. The current is opposed by the capacitance and inductance of the circuit in addition to the resistance. The total opposition to current flow is the impedance, given by the formula:
Z = R +iX
where
R is resistance,
X is reactance and
i equals
.
The real part, the resistance, represents a loss of power due to dissipation. The imaginary part, the reactance, indicates the phase difference between the voltage and current. It is either positive or negative depending on whether the current lags or leads the voltage, respectively. In a circuit containing only resistance or in a resonant circuit, the current and voltage are in phase and
Z is purely resistive. In a circuit containing only reactance, the current and voltage are out of phase and
Z is purely imaginary, i.e., there is no dissipation in the circuit. Reciprocal of admittance. Abbreviated imp.
IMPEDANCE, HIGH - Generally, the area of 25,000 ohms or higher.
