SOLUTION

A passive element is one which does not generate electricity but either consumes it or stores it. Resistors, inductors and capacitors are simple passive elements. Diodes and transistors are also passive elements.

Passive elements may either be linear or non-linear. Linear elements obey a straight-line law. For example, a linear resistor has a linear voltage vs. current relationship which passes through the origin (V = RI ). A linear inductor has a linear flux  vs. current relationship which passes through the origin ( φ = kI ) and a linear capacitor has a linear charge vs. voltage relationship which passes through the origin (q = CV ). [R, k and C are constants.]

Resistors, inductors and capacitors may be linear or non-linear, while diodes and transistors are always non-linear.