(a) The ohm's law states that the current carrying in a conductor is directly proportional to the voltage applied across the ends of the conductor, keeping the resistance constant.
Circuit Diagram
According to ohm's law; $\mathrm{V}\propto \mathrm{I}$
Mathematically; $\mathrm{V}=\mathit{ℝ}$
where, $\mathrm{V}=$ Voltage applied in volts
$\mathrm{I}=$ Current flowing in circuit in amperes.
$\mathrm{R}=$ Resistance of conductor (proportionality constant)
Graphically; slope of will determine resistance of conductor.(b) Given, current flowing through conductor

Potential difference across conductor $\left(\mathrm{V}\right)$ $=1.4\mathrm{V}$
We know, according to ohm's law, $\mathit{V}=\mathit{I}\mathit{R}$
$\Rightarrow 1.4\mathrm{V}=\left(0.35\mathrm{A}\right)\times \mathrm{R}$
$\Rightarrow \mathrm{R}=\left(\frac{1.4\mathrm{V}}{0.35\mathrm{A}}\right)=4\mathit{\Omega }$
Therefore, resistance of conductor is 4 ohms.