inductive time constant. The amount of time, in seconds, needed for current flowing in an inductive circuit to reach 63.2% of its maximum value. The inductive time constant, in seconds, may be found by dividing the circuit inductance, in henries, by the circuit resistance, in ohms:
TC = L / R
TC = Time constant in seconds
L = Inductance in henries
R = Resistance in ohms

inductive tuning. A method of selecting the frequency to which a radio-frequency circuit is resonant by changing the inductance in a tuned circuit. The resonant frequency of an L-C circuit (a circuit that contains both inductance and capacitance) can be changed by changing the amount of either the inductance or the capacitance.
The inductance is normally changed by moving a powdered iron slug into or out of the coil. Moving the slug into the coil increases the inductance, and pulling the slug out of the coil decreases the inductance.
inductor. A coil of wire used to produce inductance in an electrical circuit. The amount of inductance is determined by the number of turns of wire in the coil, by the ratio of the diameter of the coil to its length, and by the type of material used as the core of the coil. Inductance is measured in henries, millihenries, or microhenries.

industrial diamond. A diamond that is not of gem quality, but because of its hardness, is used as an industrial cutting tool.
inert-gas shielded-arc welding. A form of electric arc welding in which the arc is formed inside a shield of inert gas, such as argon or helium.
The inert gas drives all the oxygen away from the arc and prevents oxides from forming in the molten metal.
inert gas. A gas that has a stable atomic structure. Its valence shell neither tries to gain nor lose electrons. An inert gas has no tendency to unite with other elements to form chemical compounds. Helium, neon, argon, krypton, xenon, and radon are inert gases.
inertia. A characteristic of all matter that causes an object to try to remain in its present condition. If the object is at rest, not moving, its inertia tries to keep it at rest. But if it is moving, its inertia tries to keep it moving — in the same direction, and at the same speed.
inertial navigation system (navigation system). A computer-based navigation system that tracks the movement of an aircraft by signals produced by onboard accelerometers. The initial location of the aircraft is entered into the computer, and all movement of the aircraft is sensed and used to keep the position updated. An INS does not require any inputs from outside signals.
inertia starter (reciprocating engine starter). A type of starter used on some large reciprocating engines. Energy is stored in a spinning flywheel by an electric motor or a hand crank. When enough energy has been put into the flywheel, it is coupled to the crankshaft, and turns it fast enough for the engine to start.