The $V-I$ graphs for two wires $A$ and $B$ are shown in the figure. If we connect both the wires one by one to the same battery, which of the two will produce more heat per unit time? Give justification for your answer.

(B) The heat produced per unit time is given by the power formula $P = \frac{V^2}{R}$, where $V$ is the potential difference and $R$ is the resistance.
Since both wires are connected to the same battery, $V$ is constant for both.
Therefore, $P \propto \frac{1}{R}$, meaning the wire with lower resistance will produce more heat.
In a $V-I$ graph, the slope represents the resistance $(R = \frac{V}{I})$. The slope of wire $A$ is greater than the slope of wire $B$, which means $R_A > R_B$.
Since $R_B < R_A$, wire $B$ will have a lower resistance and thus will produce more heat per unit time.