Precision in Measuring Length

Measuring length is one of the fundamental aspects of physics and engineering. The accuracy and precision of any measurement depend on the instrument used to take the measurement. Precision refers to the degree of exactness with which a measurement is made. The most precise instrument for measuring length is the one that has the smallest least count.

Definition of Least Count

Least count refers to the smallest measurement that an instrument can make. For example, if the least count of a measuring instrument is 0.1 cm, then the instrument can measure lengths that are multiples of 0.1 cm. The smaller the least count, the more precise the instrument.

Comparison of Instruments

a) Metre Rod of Least Count 0.1 cm

A metre rod is a simple instrument used to measure length. It is a straight rod that is one metre in length. The least count of a metre rod is usually 0.1 cm. This means that the rod can measure lengths that are multiples of 0.1 cm. However, the metre rod is not a very precise instrument for measuring length.

b) Vernier Callipers of Least Count 0.01 cm

A vernier caliper is a more precise instrument for measuring length. It consists of two jaws, an upper and a lower, that can be adjusted to fit the object being measured. The jaws are connected to a scale that can be read to the nearest 0.1 mm. The least count of a vernier caliper is 0.01 cm, which means that it can measure lengths that are multiples of 0.01 cm.

c) Screw Gauge of Least Count 0.001 cm

A screw gauge is the most precise instrument for measuring length. It consists of a U-shaped frame with a screw attached to one end. The screw has a scale that can be read to the nearest 0.01 mm. The least count of a screw gauge is 0.001 cm, which means that it can measure lengths that are multiples of 0.001 cm.

Conclusion

In conclusion, the screw gauge is the most precise instrument for measuring length because it has the smallest least count. The smaller the least count, the more precise the instrument. While a metre rod and vernier calipers can also be used to measure length, they are not as precise as a screw gauge.