Non-ohmic conductors, also known as non-ohmic materials or non-ohmic devices, are materials or components that do not follow Ohm's Law. Ohm's Law states that the current passing through a conductor is directly proportional to the voltage across it, given a constant temperature. Mathematically, Ohm's Law is expressed as:
=
I=
R
V
Where:
I is the current flowing through the conductor,
V is the voltage across the conductor, and
R is the resistance of the conductor.
In non-ohmic conductors, the relationship between current and voltage is not linear, which means the resistance is not constant. Instead of a fixed resistance value, the resistance changes as the current and voltage change.
Non-ohmic behavior is often observed in materials that have complex charge-carrier mobility, such as semiconductors, diodes, and certain types of ionized gases. Some common examples of non-ohmic conductors include:
Semiconductors: Materials like silicon and germanium exhibit non-ohmic behavior because their resistance changes with temperature and doping levels. Their conductivity can be manipulated by adding impurities, which affects the number of charge carriers and thus the resistance.
Diodes: A diode is a semiconductor device that allows current to flow in only one direction. The relationship between voltage and current in a diode is nonlinear. When a diode is forward-biased (positive voltage applied to the anode), it conducts current, but when it is reverse-biased (negative voltage applied to the anode), it has very high resistance and blocks current flow.
Gases: In ionized gases, such as those found in fluorescent lights or gas discharge tubes, the relationship between voltage and current is not linear due to the complex interactions between ions and electrons within the gas. As the voltage increases, the gas ionizes more, and the resistance decreases.
Certain Electrolytes: Electrolytes, especially those with non-uniform concentrations of ions, can exhibit non-ohmic behavior due to the varying ionic mobility and chemical reactions that occur as current passes through them.
It's important to note that Ohm's Law is a simplification that holds true only for linear, homogeneous conductors under constant temperature conditions. Non-ohmic behavior is often the result of complex interactions between charge carriers and their environment. In practical applications involving non-ohmic conductors, more advanced circuit analysis techniques and models are needed to accurately predict their behavior.