Final answer:
The slope of a graph plotting voltage against current represents the resistance in a circuit, as defined by Ohm's law.
Step-by-step explanation:
In physics, the slope of the line on a graph plotting voltage (V) on the x-axis and current (I) on the y-axis represents the circuit's resistance (R). This is derived from Ohm's law, which states that V = IR. To find the resistance using a graph, one can measure the rise over the run (the change in current over the change in voltage) to calculate the slope, which equates to resistance. For example, if the line rises by 1 mA (0.001 A) for every 1 V increase in voltage, the slope (resistance) would be 1 Ω (ohm).