CBSE Class 10 Science 2019 · Paper 31/5/1 · Question 25(b)

(i) The graph is a straight line passing through the origin, so the current through the resistor is directly proportional to the potential difference across it ($I\propto V$, Ohm's law); the ratio $\frac{V}{I}$, the resistance, is constant. (ii) $R=\frac{V}{I}=\frac{1\text{V}}{0.1\text{A}}=10\Omega$, so at $2.5$ V the current is $I=\frac{V}{R}=\frac{2.5}{10}=0.25$ A.