Question

What is mainly measured by potentiometer?

• A. Current
• B. Resistance
• C. Potential difference
• D. All of these

Hint:

Remember that a potentiometer is superior to a voltmeter because it measures the potential difference without drawing any current from the source circuit at the balance point. This avoids the loading effect that can cause a voltmeter to read a slightly lower voltage.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
A potentiometer is a device used for accurately measuring an unknown electromotive force (e.m.f.) or potential difference by balancing it against a known potential difference.
It operates on the principle of null deflection, meaning it draws no current from the circuit being measured at the point of balance.
Step 2: Detailed Explanation:
The working principle of a potentiometer is that the potential drop across any portion of a wire of uniform cross-section and composition, carrying a constant current, is directly proportional to its length.
When we measure the potential difference of a cell using a potentiometer, we find a "null point" on the potentiometer wire where the galvanometer shows zero deflection.
At this null point, the potential difference of the cell is exactly equal to the potential drop across that length of the potentiometer wire.
Since no current is drawn from the cell at this point, the measurement is of the true e.m.f. or potential difference, making it more accurate than a standard voltmeter.
While it can be adapted to measure current and resistance indirectly, its primary and main function is the precise measurement of potential difference.
Step 3: Final Answer:
Based on its principle and primary application, a potentiometer is mainly used to measure potential difference. Therefore, option (C) is the correct answer.