Tools

SCALES

Procedure

Experiment 1- To construct a scale of 1:50 to read meters and decimeters and long enough to measure 9 m.

  1. Calculate length of the scale (l) using the formula-
    Lenght of the scale=R.F.×Maximum Length (Rounded of to next higher whole number) (If the maximum length is not known take length of the scale = 15cm to 30cm) Therefore, Length of the scale = (1/50)x(9x100)cm = 18cm
  2. Draw a line AB of 18cm long and divide into 9 equal parts. Each representing 1m.
  3. Name the divisions. Place zero at the end of the first main unit.
  4. Subdivide the division to the left of zero into10 equal parts. (Each part represents 1decimeter).
  5. Always mention the R.F. or name of the scale.

Experiment 2- Construct a diagonal scale to measure 1/25th and 1/5th of a centimeter. Assume length of scale to be 15 cm.

  1. R.F. = 1/1
  2. Given, Length of the scale = 15cm.
  3. Draw a line of 15cm, and divide it into 15 equal parts. Each part represents 1cm.
  4. Divide the first division into 5 equal parts. Each represents 1/5th of 1 centimetre, which is equal to 0.2cm.
  5. By diagonal division, divide each such part 5 equal parts. Each part represents 1/25th of 1 centimetre, which is 0.04 centimetre.
  6. Always mention the R.F. or name of the scale.

Experiment 3- Construct a vernier scale of R.F. = 1/20 to read meters and decametres and centimetres, long enough to read upto 4 metres. Show a distance of 2.38 metres on the scale.

  1. Given, R.F. = 1/20 Lenght of the scale=R.F.× Maximum Length (Rounded of to next higher whole number) Therefore, Length of the scale = (1/20)x(4x100)cm = 20cm
  2. Draw a line of 20cm and divide it into 4 equal parts. Each part represents 1 meter.
  3. Divide the first part into 10 equal parts or divisions. Each division represents 10 cm. 10 cm = 0.1m = 1 m.s.d. (main scale division)
  4. Construct the forward reading vernier along with the main scale. Make the following calculations: Least Count (LC) = 1 m.s.d. – 1 v.s.d.
          1/10 m.s.d.  =  1 m.s.d. – 1 v.s.d.
                or 1 v.s.d   =  1 – (1/10) m.s.d. =   9/10 m.s.d
                or 10 v.s.d.  =   9 m.s.d
  5. Starting at zero division mark at main scale, take a length of 9 m.s.d. and divide it into 10 equal parts.
  6. Each division represents 1 v.s.d. or 0.09 m or 9 cm.
  7. Make the following calculations: 1 v.s.d. = 0.09 m 2 v.s.d. = 2 x 0.09 m = 0.18 m
  8. Thus subtracting 0.18 m from 2.38 m (required distance), we get 2.2 m.
  9. This distance can be easily shown on the main scale.
  10. The sum of the distances from steps 8 and 9 is the required distance.