Page 46 - Physics

Physics for Secondary Schools

5. When a screw gauge with a least 2. Hold the steel ball in the gap while
count of 0.01 mm is used to measure rotating the thimble clockwise until
the diametre of a wire, the reading it gently grips the ball.
on the sleeve is found to be 0.5 mm 3. Keep rotating the ratchet knob until
it clicks.
and the reading on the thimble is 4. Record your observations.
found to be 27 divisions. What is the 5. Unscrew the thimble slightly. Free
correct diametre of the wire, if the the ball and turn it through a certain
zero error for the gauge is -0.005 cm? angle. Then repeat step 3 and 4.
6. Repeat step 5 for different rotation
Acti vity 2.3 angle.
7. Re-measure the diametre of the steel
Aim: To measure the diametre ball using the vernier calliper and
of a steel ball using a record your readings.
micrometre screw gauge. Questions

Materials: Micrometre screw gauge (a) Calculate the average of the obtained
and steel ball readings.
Procedure (b) Why would you prefer a micrometre
screw gauge over a vernier calliper
1. Unscrew the thimble to create a gap when measuring the diametre of a
between the anvil and the spindle. steel ball?

A micrometre screw gauge is more accurate than a vernier calliper. It measures up to
three decimal places in the unit of mm. This means that its degree of accuracy is to the
nearest thousandth of a centimetre. Unlike a micrometre screw gauge, a vernier calliper

can only measure to a hundredth of a centimetre.

Task 2.5
Collect variety a of wires of different diameters, lead pencils and steel balls.

1. Find out the smallest division on the main scale of your micrometre screw gauge
and the number of divisions on the thimble.
2. Measure the diameters of the different objects. Record your fi ndings in the following
table.
Object Sleeve Thimble Vernier reading Actual diametre
reading (mm) reading (mm) (mm) (mm)
Wire 1
Wire 2
Steel ball
Lead pencil

40
Student’s Book Form One

Physics Form 1 Final.indd 40 16/10/2024 20:55