Which of the following statement is correct for a potentiometer?

The correct answer is Option (2) → It cannot measure the capacitance of a capacitor

A potentiometer is a long uniform wire carrying a steady current, so the potential falls uniformly along it. An unknown steady potential difference is balanced against a length of the wire, with no current drawn from the source at balance. Anything that can be turned into a steady potential difference can therefore be measured with it.

Option (1) It cannot measure resistance — Incorrect. It can measure resistance by comparing the balancing lengths for the drops across a known and an unknown resistance carrying the same current.

Option (2) It cannot measure the capacitance of a capacitor — Correct. A capacitor in a steady circuit carries no steady current and has no steady drop proportional to its capacitance, so the potentiometer has no way to measure capacitance.

Option (3) It cannot measure current — Incorrect. It can measure current by balancing the drop across a known standard resistance through which the current flows, \( I = V/R \).

Option (4) It cannot measure potential difference — Incorrect. Measuring potential difference is its main use, more accurately than a voltmeter.