How can we increase the relative accuracy of measurement by a screw gauge ?

Options

A. By increasing the size of pitch
B. By increasing the number of divisions on the circular scale
C. By taking large number of observations
D. By having a device free of zero error.

Explanation

To increase the relative accuracy of measurement by a screw gauge, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Accuracy**:
- Accuracy in measurement refers to how close a measured value is to the actual (true) value. It is influenced by the precision of the measuring instrument.

2. **Identify the Factors Affecting Accuracy**:
- The accuracy of a screw gauge depends on its least count, which is the smallest measurement that can be accurately read from the scale. The least count is determined by the formula:
\[ \text{Least Count} = \frac{\text{Smallest Main Scale Reading}}{\text{Number of Divisions on Circular Scale}} \]

3. **Increasing the Number of Divisions**:
- By increasing the number of divisions on the circular scale, the least count decreases. A smaller least count allows for more precise measurements, thus increasing the relative accuracy of the screw gauge.

4. **Taking Multiple Observations**:
- While taking a large number of observations can help in reducing random errors and improving reliability, it does not inherently increase the accuracy of the measurements. It can help in averaging out errors but does not change the precision of the instrument itself.

5. **Zero Error Consideration**:
- Ensuring that the screw gauge is free from zero errors is important for accurate measurements. However, this is more about calibration than increasing accuracy through design.

6. **Conclusion**:
- The most effective way to increase the relative accuracy of a screw gauge is to **increase the number of divisions on the circular scale** (Option B). This directly reduces the least count and improves measurement precision.

### Final Answer:
To increase the relative accuracy of measurement by a screw gauge, the best approach is to **increase the number of divisions on the circular scale**.

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