Explanation

(b) The resistance of a metallic wire at temperature $t{^\circ}C$ is given by
$R_{t} = R_{0}(1 + \alpha t)$
Where $\alpha$ is coefficient of expansion.
Hence, resistance of wire increases on increasing the temperature. Also, from Ohm’s law, ratio of $\frac{V}{i}$ is equal to R $ie$,
$\frac{V}{i} = R$
Hence, on increasing the temperature the ratio$\frac{V}{i}$ increases.