# Id

**ID**- Abbreviation of Inner Diameter.
**Ideal Driver**- A speaker driver that delivers excellent performance in terms of polar response, power handling, efficiency, frequency range and reliability.
**Ideal Gas**- The particles have no internal structure, are indestructible, do not interact with each other except when they collide, and all collisions are elastic.
**Ideal Gas Constant**- Also known as Molar Gas Constant.
**Ideal Gas Law**- Gases obey the gas laws at low pressures and at temperatures above those at which they liquefy.
**Ideal Solution**- All molecules interact in exactly the same way; the solvent-solvent, solvent-solute, and solute-solute intermolecular forces are all equivalent.
**Idempotent Law**- Combining a quantity with itself either by logical addition or logical multiplication will result in a logical sum or product that is the equivalent of the quantity.
**Identity**- A number that when an operation is applied to a given number yields that given number. For multiplication, the identity is one and for addition the identity is zero.
**Identity Law**- States that any expression is equal to itself.
**Idle**- Internal combustion engine operating at no load and minimum engine speed.
**Idler Frequency**- In a parametric amplifier, the difference between the input signal and the pump
signal frequency.
**Idler Gear**- An idler gear may be used between two gears so that the direction of rotation on the two shafts is in the same direction.