Question

A potentiometer can be used to measure
A. emf of newly designed cell
B. internal resistance of a cell
C. unknown resistance
D. potential difference across a resistor

Answer 1

Hint: A potentiometer measures the voltage of a cell by comparing it with a known reference voltage.

Complete step by step solution:
We know that,
A potentiometer is an instrument for measuring voltage or 'potential difference' by comparison of an unknown voltage with a known reference voltage.
If a sensitive indicating instrument is used, little current is drawn from the source of the unknown voltage. Since the reference voltage can be produced from an accurately calibrated voltage divider, a potentiometer can provide high precision in measurement.
Potentiometer is a device used to measure the emf of the cell, potential difference across two terminals, unknown resistance, and internal resistance of the cell.

Therefore, the correct options are A, B, C and D

Additional information:
The principle of a potentiometer is that the potential dropped across a segment of a wire of uniform cross-section carrying a constant current is directly proportional to its length. The potentiometer is a simple device used to measure the electrical potentials (or compare the e.m.f of a cell). One form of potentiometer is a uniform high-resistance wire attached to an insulating support, marked with a linear measuring scale. In use, an adjustable regulated voltage source E, of greater magnitude than the potential to be measured, is connected across the wire to pass a steady current through it.

Note: Between the end of the wire and any point along it will be a potential proportional to the length of wire to that point. By comparing the potential at points along the wire with an unknown potential, the magnitude of the unknown potential can be determined. Students often go wrong in the various steps involving the solving of the sum.