The random error which exists invariably in screw gause

Options

A. least count error
B. zero error
C. gross error
D. backlash error

Answer

To solve the question regarding the random error that exists invariably in a screw gauge, we will analyze the options provided and identify the correct answer step by step.

### Step-by-Step Solution:

1. **Understanding Random Errors**:
Random errors are fluctuations in measurements that occur due to unpredictable variations in the measurement process. They can arise from various sources, including the measurement instrument, the environment, and the observer.

**Hint**: Consider what types of errors can occur during the measurement process.

2. **Identifying the Options**:
The options given are:
- A) Least Count
- B) Zero Error
- C) Gross Error
- D) Backlash Error

**Hint**: Think about what each term means in the context of measurement.

3. **Analyzing Each Option**:
- **Least Count**: This is the smallest value that can be measured by the instrument. It is not an error but rather a characteristic of the measuring device.
- **Zero Error**: This occurs when the instrument does not read zero when it should. It is a systematic error, not a random error.
- **Gross Error**: This refers to mistakes made by the observer or instrument, such as misreading the scale. It is also not a random error.
- **Backlash Error**: This is a specific type of error that occurs in instruments like screw gauges when there is a play or slack between the moving parts. It happens when the screw is rotated quickly, leading to a slipping effect that causes inaccuracies in measurement.

**Hint**: Focus on which option describes an error that is inherent and random in nature.

4. **Conclusion**:
After analyzing the options, we find that the only option that describes a random error that exists invariably in a screw gauge is **Backlash Error**. This error arises from the mechanical design of the screw gauge and is influenced by how quickly the screw is turned.

**Final Answer**: The random error that exists invariably in a screw gauge is **Backlash Error (Option D)**.