**Ideal transformer**

A transformer characterized by no winding resistance, no leakage ﬂux, and a lossless and inﬁnitely permeable magnetic core.

**Identity, or unit, matrix**

A diagonal matrix whose elements in the principal diagonal are all equal to unity and all elements not in the principal diagonal are equal to zero.

**Induction machine**

An asynchronous AC machine that comprises a magnetic circuit interlinked with two electric circuits, rotating with respect to each other, and in which power is transferred from one circuit to another by electromagnetic induction.

**Imperial Units **

** **These are the measurement units used in the United States. Typical units are feet, inches, pounds, and horsepower.

**Ideal voltage source**

An active element (two terminal) which maintains specified voltage and is independent of rest of the circuit elements, with zero internal resistance.

**Insulator**

Materials that have no free electrons and thus prevent the passage of electric current.

**Ideal current source**

An active element (two terminal) which keeps the value of the current constant in spite of voltage across the terminals, with infinite internal resistance.

**Impedance**

Impedance is the combined resistance in the flow of current because of resistive and reactive elements in the circuit.

**Inductance**

Inductance is the property of an element to store energy in a magnetic field.

**Inductive Reactance**

Opposition to the flow of an alternating current by the inductance of a circuit; equal to 2πfL and measured in ohms.