Question

What is an Ohmic resistor?

Answer 1

Ohm’s law gives relation between current, voltage and resistance. Keeping resistance as a constant quantity for particular material, you can plot a straight line graph. Conductors which do possess straight line graphs can be known as ohmic. If Resistance is constant for a particular conductor then current increases with increase in voltage.

Complete answer:
The relationship between current through a conductor and applied potential difference was first discovered by German scientist George Simon Ohm in 1828.
The relationship between current through a conductor and applied potential difference is known as Ohm’s law.
The conductors or material, obey Ohm's law are called ohmic resistors.
As long as the physical state (material, dimensions and temperature) of a conductor remains the same, the electric current flowing through a given conductor is directly proportional to the potential difference applied across it.
$\begin{aligned} & I\alpha V \\\ & I=\dfrac{V}{R} \\\ & \text{ or V=IR} \\\ \end{aligned}$
Where $\text{R}$is constant of proportionality. It represents the opposition to flow of current and is known as ‘resistance’.
$R=\dfrac{V}{I}$
If we keep resistance constant then from above equation, we can say that
$V\alpha I$
It means as voltage is increased then current will also increase. I.e. The ratio of$V$and$I$is resistance and is constant for particular material.
For such a resistor which follows ohm's law, the graph of electric current versus potential difference across the conductor is straight line.

In general, resistance is given by the ratio of applied potential difference across the conductor to the resulting current through it.
$\begin{aligned} & R=\dfrac{V}{I}=\dfrac{1}{\text{Slope of I-V characteristic}} \\\ & \text{SI unit of resistance is ohm(}\Omega \text{)}\text{.} \\\ & \text{1ohm=}\dfrac{1\text{volt}}{1\text{ ampere}} \\\ \end{aligned}$
Given is the graph of V verses I.
From the above theory, we can conclude that it is a straight line.
Ratio of V and I is resistance and it remains constant for particular material.
And if $V\text{ }=\text{ }IR$so if Resistance is constant for a particular conductor then current increases with increase in voltage.

Note:
Straight graph is applicable only for particular material only known as ohmic material also. In the same graph, if resistance has taken from different materials then the graph will not be straight. If a potential difference of 1 volt across a conductor produces a current of 1 ampere through it, then the resistance of the conductor is 1 ohm. Reciprocal resistance is called conductance. SI unit is Siemens$\left( S\text{ or oh}{{\text{m}}^{-1}} \right)$ .