What is a nonlinear element?

A nonlinear element refers to components in electrical circuits where the relationship between voltage and current is not proportional. This means that as the voltage across the element changes, the current flowing through it does not change in a linear fashion.

In this context, a conductor, semi-conductor, or solid-state device whose resistance varies with the voltage applied exemplifies this concept. For instance, in a diode or transistor, the current does not increase proportionately with a rise in voltage, showcasing nonlinear behavior. These types of elements are crucial in various applications for processes such as amplification and switching.

Conversely, a conductor with constant resistance does not demonstrate nonlinear characteristics since its behavior follows Ohm's law directly, demonstrating linearity. A component that only allows current to flow in one direction is a specific function of devices like diodes but does not fully encapsulate the broader idea of nonlinearity as it doesn’t address the voltage-current relationship. Similarly, while passive components that store energy (like capacitors and inductors) play essential roles in circuits, they typically exhibit linear behavior under standard conditions, thus not fitting the definition of nonlinear elements.