Ohm's law can be applied to _____ only.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Resistance
Ohm’s law says that the current through a conductor is proportional to the potential difference across it, \(V=IR\), with the resistance \(R\) staying constant as long as the temperature does not change. It holds for ohmic conductors — metal wires and resistors — whose resistance does not depend on the current, so a graph of \(V\) against \(I\) is a straight line.
Why the other options are incorrect
Option (1) Semiconductor — Incorrect. Its current rises far faster than the voltage (a diode even conducts in one direction only), so \(V\)–\(I\) is not a straight line.
Option (3) Insulator — Incorrect. It carries practically no current until it breaks down at a high voltage.
Option (4) Gases — Incorrect. A gas conducts only after it is ionised by a high voltage, and the current then does not grow in proportion to the voltage.