Which of the following statements is not true with reference to a pot…

The correct answer is Option (1) → It is based on balanced Wheatstone bridge.

A potentiometer works on the principle that, for a steady current through a uniform wire, the potential drop across a length of the wire is proportional to that length (\( V \propto l \)). An unknown emf is found by moving the jockey until the galvanometer shows no deflection (a null method).

Option (1) It is based on balanced Wheatstone bridge. — This statement is not true, so it is the answer. The potentiometer compares a potential difference with the fall of potential along a uniform wire; the metre bridge, not the potentiometer, is based on the Wheatstone bridge.

Option (2) It draws no current from the voltage source being measured. — This is true. At the balance point the galvanometer current is zero, so no current flows through the source.

Option (3) It is unaffected by the internal resistance of the source. — This is true. With no current through the source there is no drop across its internal resistance.

Option (4) It is a very sensitive device to measure potential difference. — This is true. A long wire gives a small potential drop per unit length.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Potentiometer – “… The potentiometer has the advantage that it draws no current from the voltage source being measured. As such it is unaffected by the internal resistance of the source.”