Ohmic conductor
A conductor obeying Ohm's law, with resistance independent of applied potential difference and current. Its I-V characteristic is a straight line passing through the origin. Metals like copper and constantan at constant temperature are ohmic.
Formula
R = V/I (constant)
Real World
Constantan wire (a nickel-copper alloy) is used in precision resistors in laboratory equipment because its resistivity barely changes with temperature, keeping resistance constant across a wide range.
Exam Focus
Distinguish ohmic from non-ohmic by checking whether the I-V graph is a straight line through the origin — a curve or kink means non-ohmic.
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