Question

Which conductors do not obey Ohms law?

Answer 1

Not all conductors obey Ohm's Law. Ohm's Law states that the current passing through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance (I = V/R). However, some materials do not follow this relationship. These are known as non-ohmic conductors.

Here are a few examples of conductors that do not obey Ohm's Law:

1. Semiconductors: Materials like silicon and germanium, which are used in electronic devices like diodes and transistors, do not follow Ohm's Law. Their resistance changes with temperature, voltage, and the type of impurity added to them. The relationship between current and voltage is non-linear.
   

1. Thermistors: These are resistors whose resistance changes significantly with temperature. For example, Negative Temperature Coefficient (NTC) thermistors decrease in resistance as the temperature increases, and Positive Temperature Coefficient (PTC) thermistors do the opposite. Their current-voltage relationship does not follow Ohm’s Law.
   

1. Diodes: A diode is a semiconductor device that only allows current to flow in one direction. Its current-voltage characteristic is non-linear, meaning it does not obey Ohm’s Law.
   

1. Superconductors: Below a certain critical temperature, superconductors have zero resistance, meaning they don't have a regular relationship between voltage and current as described by Ohm's Law.
   

1. Non-metallic conductors: Some non-metallic materials, such as electrolytes or ionic solutions, can also show non-linear I-V characteristics, and thus do not obey Ohm's Law.
   

In these cases, the current and voltage do not have a simple proportional relationship like Ohm's Law suggests.