Question

Which of the following is an ohmic resistance?
A. Diode valve
B. Junction diode
C. Filament of a bulb
D. Nichrome

Answer 1

Hint: There are two types of material classified based on their behavior on passing electricity through them. It is practically observed that certain materials behave differently when electric current is passed through them. A light bulb is a simple example of this behavior.

Complete step by step answer:
The materials are classified in two categories based on their behavior when current is passed through them. The two categories are: Ohmic and non-Ohmic resistances.
Ohmic resistances: The material or resistance which obeys Ohm’s law i.e. V = iR are said to be ohmic resistance. It must be noted that the resistance for ohmic resistances with time.
Non-Ohmic resistances: The material or resistance which obeys Ohm’s law are said to be non-ohmic resistance. For example: A light bulb has a filament which has certain resistance due to which it converts electrical energy into light and heat energy. This heat energy increases the resistance of the filament. Hence the resistance is no more constant after the application of potential difference.
Experimentally, it can be understood that nichrome wire acts as an ohmic resistance. If we double the potential difference across this wire, the current will also be doubled.

Note:
These facts can be proved only experimentally. During experiments, we plot a graph of current corresponding to a particular potential difference. For ohmic devices the graph must be a straight line passing through the origin. Whereas for non ohmic resistance, this behavior is deviated. The graph in case of a non ohmic resistance is not a straight line, rather is a curve.