Ohmic vs Non Ohmic Conductors
Electricity is flow of electrons and there are some substances that do not allow electricity to be passed through them and are known as non conductors. But there are some, such as metals, that are good conductors of electricity. Between these conductors also, there is a classification of Ohmic and non Ohmic conductors. To understand the differences between Ohmic and non Ohmic conductors, we first need to look at ohms law.
Ohm’s law says that the current flowing through a conductor is proportional to the voltage provided other factors such as temperature are kept under control or are constant. Now the conductors that obey this law are called Ohmic conductors while those who do not follow this law are called non Ohmic conductors. Pure metals such as copper and tungsten are Ohmic conductors as they obey the law completely. These conductors need constant pressure and temperature to follow ohm’s law. Their resistance does not vary with current and remains constant. However, the strength of current also needs to be low or otherwise they will lose this property of being Ohmic conductors. This is known as heating effect.
In metals, there are free electrons that are responsible for carrying current. These free electrons vibrate and often collide with each other and also with electrons of nearby atoms thus releasing kinetic energy. When this energy is lost as heat, it makes it difficult for the electrons to pass through and the resistance of the metal increases with increased temperature. This is when the conductor becomes a non Ohmic conductor. For example, tungsten that is used in a filament bulb is a Ohmic conductor and allows for passage of current but becomes a non Ohmic conductor when its temperature increases and it begins to glow.
• Conductors that obey Ohm’s Law are called Ohmic conductors while those that do not obey Ohm’s Law are called non Ohmic conductors.
• Magnitude of current remains unchanged when current or voltage is reversed in Ohmic conductors; the magnitude changes in the case of non Ohmic conductors.
• In Ohmic conductors, current is proportional to voltage whereas this is not the case with non Ohmic conductors
• In Ohmic conductors, temperature affects current and resistance whereas in non Ohmic conductors, different factors affect current and resistance.