What is a nonlinear resistor?
Resistors with different resistances for different end currents are referred to as non-linear resistors. For such a resistor, the resistance is a function of the current flowing in the device. A simple example of a nonlinear resistor is an incandescent lamp. Since it is not a constant value, it is more difficult to analyze a circuit that contains nonlinearities.
In fact, all of the actual resistors are non-linear because the electrical performance of all the resistors is affected by environmental factors such as temperature. However, many materials in the specified working range very close to the ideal linear resistor. Focus on this type of element and just call them resistors. Since the R value can vary from zero to infinity, it is important for us to study the possible R-values for both limits. An element with R = 0 is referred to as a short circuit, and in practice, a short circuit usually refers to a connecting wire that is assumed to be an ideal conductor. Thus, the short circuit is a circuit element whose resistance is approximately zero. Similarly, an element with R = ∞ is called an open circuit.