A student plots current versus potential difference for two conducting samples
PHYSICS · Single correct · A Level · Physics · Electricity · Electricity
Problem
A student plots current versus potential difference for two conducting samples. Sample X produces a straight line through the origin, whereas Sample Y produces a curve whose slope increases with ΔV. Which statement best explains why only Sample X is classified as ohmic?
(a) Sample X carries the larger current for the same potential difference, so it must be the better conductor and therefore ohmic.
(b) Because Sample X’s graph passes through the origin, its resistance is zero at ΔV=0, and materials that reach zero resistance are classified as ohmic.
(c) For Sample X, the ratio ΔV/I remains constant, indicating a constant resistance.
(d) Sample X’s straight-line graph shows it has a smaller resistance than Sample Y; lower resistance materials are, by definition, ohmic.