Question

Potentiometer measures potential difference more accurately because
A. it measures potential in the open circuit
B. it uses sensitive galvanometer for null condition
C. it uses high resistance potentiometer wire
D. it measures potential in the closed circuit

Answer 1

Hint: The potentiometer measures potential difference by using a galvanometer. A galvanometer works in the balanced condition and indicates null condition or zero current.

Complete step by step solution:
In a potentiometer, the potential to be measured is connected across a slide wire with a movable jockey connected with a galvanometer and other circuit components. The galvanometer shows zero deflection (no current is drawn) for a particular position of the movable jockey on the slide wire. In this position, the potential drop across the length of the slide wire is exactly equal to the potential to be measured. The wire has uniform thickness and area of cross-section and hence it has uniform resistance per unit length. A calibrated scale is placed along the slide wire for accurate measurement. As the resistance is known, the voltage drop across the wire can be adjusted accurately by adjusting the working current. As the circuit is open (no current in balanced condition), the accuracy of measurement is more as compared to other methods.

The correct answer is option A.

Additional information: There are two main types of potentiometers:
(i) Rotary potentiometer
(ii) Linear potentiometer.
A potentiometer can be used to compare the emf of a battery cell with a standard cell, measure the internal resistance of a battery cell and measure the voltage across a branch of a circuit.

Note: A voltmeter draws current when measuring the potential drop. There is some potential drop due to the internal resistance of the cell and hence the reading is not accurate.