Step 1: Understanding the measurements.
In a screw gauge, the pitch is the distance moved by the spindle per rotation, and the circular scale gives the additional precision. Here the pitch is 0.1 mm, and there are 100 divisions on the circular scale.
The reading of the screw gauge consists of two parts:
1. Main Scale Reading (MSR): This is the reading of the linear scale, which in this case is 5 mm.
2. Circular Scale Reading (CSR): This is the fractional part that gives additional precision. The circular scale's 50th division coincides with the zero of the main scale.
Step 2: Calculate the circular scale reading.
Each division on the circular scale represents \( \frac{\text{pitch}}{\text{number of divisions}} = \frac{0.1 \, \text{mm}}{100} = 0.001 \, \text{mm} \).
Thus, the CSR for the 50th division is:
\[
\text{CSR} = 50 \times 0.001 \, \text{mm} = 0.05 \, \text{mm}
\]
Step 3: Calculate the total reading.
The total diameter of the sphere is the sum of the main scale reading and the circular scale reading:
\[
\text{Diameter of sphere} = \text{MSR} + \text{CSR} = 5 \, \text{mm} + 0.05 \, \text{mm} = 5.05 \, \text{mm}
\]
Final Answer: 5.045 mm