What is meant by Least Count (LC) of a measuring instrument?

The Least Count (LC) of a measuring instrument, also known as the smallest readable or measurable value, is the smallest change in the quantity being measured that can be detected or displayed by the instrument. In other words, it represents the instrument's ability to make precise measurements.

The concept of least count is particularly important in fields where accuracy and precision are crucial, such as science, engineering, and metrology (the science of measurement). Here are a few key points to understand about the least count of a measuring instrument:

Measurement Scale: The least count is associated with the measurement scale or graduations of the instrument. For example, on a ruler, if the smallest division between two markings is 1 millimeter, then the least count of the ruler is 1 millimeter.

Significance: Knowing the least count is essential for making accurate measurements. It helps users understand the level of precision they can achieve with the instrument.

Formula: The least count can be calculated using the formula:

Least Count (LC) = Range / Total Number of Divisions on the Scale

Where:

Range is the maximum value that the instrument can measure.
Total Number of Divisions on the Scale represents the number of equally spaced divisions or markings on the instrument's scale.
Example: Let's say you have a vernier caliper with a main scale that goes up to 10 centimeters and a vernier scale divided into 10 equal parts that fit between two main scale markings. In this case, the range is 10 centimeters, and there are 10 divisions on the vernier scale. The least count would be:

LC = 10 cm / 10 = 1 cm / 10 = 0.1 cm or 1 millimeter

So, the least count of this vernier caliper is 0.1 centimeters or 1 millimeter, which means it can measure length increments as small as 1 millimeter.

Accuracy and Precision: A smaller least count indicates a more precise instrument because it can detect smaller changes in the measured quantity. However, a smaller least count doesn't necessarily guarantee accuracy; it depends on the instrument's calibration and design.

In summary, the least count of a measuring instrument is the smallest measurement that can be reliably made with that instrument. It is a critical factor in determining the precision of measurements and is an important consideration when choosing and using measuring tools in various fields of science and engineering.