10.3.2—The principle of the potentiometer as a means of comparing potential
- Syllabus
- 9702–2028–2029
- Objective
- 10.3.2
- Level
- AS
A potentiometer compares potential differences by balancing a test voltage against a uniform wire drop
A potentiometer uses a uniform resistance wire so p.d. is proportional to length; a balance point compares an unknown p.d. with a known reference.
At balance, the detector carries no current, so the comparison is not disturbed by the test source. Keep wire current and uniformity conditions clear.
If a 1.20 V reference balances at 60 cm and an unknown balances at 45 cm on the same wire, the unknown is 0.90 V.
The balance length is not itself a voltage; proportionality requires the same wire current and uniform resistance per unit length.
ConceptA-Level CAIE Physics AS