Question

Given below are two statements:
Statement I: The accuracy of null type instruments is higher than that of deflection type instruments
Statement II: Null type instruments are more suitable to dynamic measurements compared to deflection instruments
In light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Hint:

- Null-type $=$ High Accuracy, Low Speed (Best for static/calibration measurements).
- Deflection-type $=$ Moderate Accuracy, High Speed (Best for dynamic/real-time measurements).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Measuring instruments are broadly classified into deflection-type and null-type based on their operation:
- Deflection-type instruments determine the value of a physical quantity by the displacement of a pointer over a calibrated scale (e.g., analog voltmeters).
- Null-type instruments balance the unknown quantity against a known standard, adjusting the system until the indicator reads zero (e.g., Wheatstone bridge).

Step 2: Detailed Explanation:
Let us evaluate both statements:
- Statement I: "The accuracy of null type instruments is higher than that of deflection type instruments."
This is correct.
Null-type instruments are highly accurate because they do not rely on the calibration of spring constants or pointer mechanisms. At the null balance point, the current drawn from the measured source is zero, which eliminates loading effects and system errors.
- Statement II: "Null type instruments are more suitable to dynamic measurements compared to deflection instruments."
This is incorrect.
Null-type instruments require manual or automatic adjustment to find the balance point, which makes them slow and unresponsive to rapidly changing (dynamic) values.
Deflection-type instruments have a much faster dynamic response because the pointer reacts directly to changes in the measured quantity, making them far better suited for dynamic measurements.
Therefore, Statement I is correct, but Statement II is incorrect.

Step 3: Final Answer:
The correct option is (C).