To Determine The Cross-sectional Area Of A Given Glass Rod By Using A Micrometer Screw Gauge. | Grade Xi
0APPARATUS REQUIRED
- Screw gauge
- Glass rod
- Cotton wool
THEORY
A screw gauge is a measuring instrument that is used to measure small distances. It consists of a C-shaped frame with a fixed jaw at one end and a movable jaw at the other end. The movable jaw is attached to a lead screw, which is a screw with a fine pitch. As the lead screw is turned, the movable jaw moves a small distance along the frame.
The distance moved by the movable jaw is indicated by a scale engraved on the frame. The scale is divided into two parts, the main scale and the vernier scale. The main scale is divided into millimeters, and the vernier scale is divided into 50 equal divisions.
Each division on the vernier scale represents 0.01 millimeter. To measure the diameter of a rod using a screw gauge, the rod is placed between the jaws of the screw gauge. The movable jaw is then moved until it just touches the rod. The reading on the main scale and the vernier scale is then noted.
The reading on the main scale gives the diameter of the rod in millimeters, and the reading on the vernier scale gives the diameter of the rod in hundredths of a millimeter.
PROCESS
- Clean the glass rod and the jaws of the screw gauge with cotton wool.
- Place the glass rod between the jaws of the screw gauge.
- Turn the ratchet knob until the rod is held firmly in place.
- Read the main scale and the vernier scale.
- Record the readings in a table.
- Repeat steps 2 to 5 for a total of 10 readings.
OBSERVATIONS
The following readings were obtained:
| Reading Number | Main Scale Reading (mm) | Vernier Scale Reading (mm) | Total Reading (mm) | Diameter of Glass Rod (mm) |
|---|---|---|---|---|
| 1 | 5.0 | 0.02 | 5.02 | 5.02 |
| 2 | 5.1 | 0.04 | 5.14 | 5.14 |
| 3 | 5.2 | 0.06 | 5.26 | 5.26 |
| 4 | 5.3 | 0.08 | 5.38 | 5.38 |
| 5 | 5.4 | 0.10 | 5.50 | 5.50 |
| 6 | 5.5 | 0.12 | 5.62 | 5.62 |
| 7 | 5.6 | 0.14 | 5.74 | 5.74 |
| 8 | 5.7 | 0.16 | 5.86 | 5.86 |
| 9 | 5.8 | 0.18 | 5.98 | 5.98 |
| 10 | 5.9 | 0.20 | 6.10 | 6.10 |
CALCULATION
The average diameter of the glass rod is:
(5.02 + 5.14 + 5.26 + 5.38 + 5.50 + 5.62 + 5.74 + 5.86 + 5.98 + 6.10) / 10 = 5.55 mm
RESULTS
The average diameter of the glass rod is 5.55 mm.
PRECAUTIONS
- Make sure that the glass rod and the jaws of the screw gauge are clean before taking measurements.
- Do not apply too much force when tightening the ratchet knob.
- Read the main scale and the vernier scale carefully.
- Record the readings in a table.
- Repeat the measurements several times to get an accurate average diameter.