Methods of Measurement

Physics and measurements are used in everyday life. Physics is the study of nature and its laws. For example, knowing Newton’s principles of motion and gravitation can explain the moon’s orbit around the earth, an apple falling from a tree and the tides in the sea on a full moon night. Physics is concerned with the basic rules that govern all aspects of life. We utilise measurement in our daily lives to learn about physical quantities. This weighing equipment can measure mass. Similarly, length can be measured with a scale or tape. We will establish the units, dimensions, and formulas of physical quantities. After measuring these numbers, we will learn to calculate measurement errors and confirm our calculations.

Physical Quantity 

Physical quantities are all of the quantities in terms of which the laws of physics are explained and which can be measured directly or indirectly and are therefore classified as such. For example, mass, length, duration, speed, and force, among other things.

Following are the types of physical quantity –

• Fundamental quantities: Physical quantities that do not depend on or depend on one another are referred to as fundamental or base physical quantities in scientific terminology. Example – time, length, mass, temperature, luminous intensity, electric current etc. 
• Derived quantities: The physical quantities that are derived from fundamental quantities are referred to as derived quantities in this context. Example – force, acceleration, speed etc. 

System of Units

The process of measuring and comparing is known as the unit process. It is the quantity that is utilised as a baseline for comparison. A system of units is a collection of fundamental and derived units for all physical quantities that is complete in its scope.

• FPS (Foot-Pound-Second) System: The length unit is the foot, the mass unit is the pound, and the time unit is the second in this system.
• CGS (Centimetre-Gram-Second) System: The unit of length in this system is the centimetre, the unit of mass is the gram, and the unit of time is the second.
• MKS (Metre-Kilogram-Second) System: Mechanics is the only subject covered by this system. The unit of length in this system is the metre, the unit of mass is the kilogram, and the unit of time is the second.

S.I. (International System) Units

Distinct countries employ various measurement units. To prevent complications, seven physical quantities have been designated as fundamental or base physical quantities, with two additional physical quantities designated as supplemental. S.I. Units were introduced in 1971.

The different quantities are represented below –

Examples of Methods of Measurement 

Earth resistance measurement:

• Testing for earth resistivity may normally be done with the same instrument that is used for testing for earth resistance, with one exception: the instrument must be of the four-terminal variety, with the voltage and current connections being brought out to different terminals on the instrument. It is not possible to conduct earth resistivity testing with three terminal instruments.
• Typically, the Wenner method is used to assess earth resistivity, which entails the placement of four temporary earth spikes in the ground. The spikes do not need to be moved as part of the testing technique. However, their location and spacing are dictated by the depth at which it is necessary to establish the earth’s resistivity, typically several metres.

pH metric titration:

• The equivalence point is the most crucial piece of information to gain from an acid-base titration. An equivalence point is reached when a given number of moles of acid is introduced to the titration flask, and the corresponding number of moles of the base is poured from the buret. This allows us to determine the base’s molarity, which can be done because the number of moles of base supplied is equal to the number of moles of acid present in the flask and because the volume of the base has been added is also known. Similarly, suppose the number of moles of acid in the titration flask is unknown. In that case, the equivalence point can be estimated based on the molarity of the base and the volume of base injected if the number of moles of acid in the titration flask is known.
• At the equivalence point, the pH of a solution will frequently fluctuate drastically from its initial value. pH indicators work by changing colour when exposed to a wide variety of pH conditions. When using an indicator that changes colour around the equivalence point, there is also a dramatic change in the indicator’s colour at the equivalence point due to the quick change in pH at this point.
• A potentiometric acid-base titration does not require an indicator because of its simplicity. When a base is given to an acid solution in small increments (referred to as aliquots), the pH of the solution is measured using a pH metre. Afterwards, a graph is created, with pH represented by the vertical axis and the base volume added represented by the horizontal axis.

Conclusion

Physics is a science that is based on measurements. A measurement is a quantitative description of one or more fundamental properties compared to a reference standard or a standard deviation.  Experiments are carried out in the fields of science and engineering. It is necessary to take readings during experiments; therefore, all of these experiments necessitate measurements. This is where the significance of methods of measurement can be found.