A physics student investigates an electrical component by gradually increasing the current through it while recording the potential difference across it. The student’s measurements produce a graph of potential difference V (vertical axis, volts) versus current I (horizontal axis, amperes) that can be described verbally as follows:
• From I=0 to I=0.40A, the plot is a straight line passing through the origin.
• For currents greater than 0.40A, the curve bends upward so that V increases more rapidly than I.
• At the highest measured point (I=1.00A) the potential difference is 8.0V.
Assume the ambient temperature of the component rises noticeably as the current increases.
(a) Describe qualitatively how the slope of the V–versus–I curve changes as the current increases from 0 to 1.0A. Explain what the changing slope implies about the component’s resistance.
(b) A lab partner claims that the component obeys Ohm’s law because the graph passes through the origin. Evaluate this claim, citing specific evidence from the graph.
(c) Distinguish between the terms "average resistance" and "instantaneous resistance" for this experiment, and state which of the two would be larger at I=0.80A. Justify your answer without performing numerical calculations.
(d) Provide one plausible physical explanation, consistent with the observations, for why the resistance of the component increases at higher currents.