An Overview of the Measurements
Measurement system is used to connect the number to physical quantities and processes. There were formerly four basic measurements such as mass (weight), distance or length, area and volume (liquid or grain). However, the idea of weights and measures has widened to include diverse factors like temperature, brightness, pressure, and electrical currents measured. The fundamental idea in the study of science and Mathematics is measurement.
The qualities of an object or an occurrence can be specified so that we may compare them to those of other objects or incidents. When discussing the division of a quantity, measurement is the word that appears most frequently. Additionally, in that, it requires a specific number of items to complete a specific task. We commonly experience many measurement types for length, weight, times, etc. in our daily lives. A standard unit of measurement represents the magnitude of a quantity, even though the size, measurement, and quantity all differ. This leads to the requirement for the units of measurement for every quantity.
What is Measurement?
Measurement is a method that involves the comparison of an object's characteristics to the reference value in order to identify its attributes. The primary metric for expressing any quantity of objects, things, and occurrences is measurement. Since there is no way to make a proper comparison, the measurements always contain an error, which is the difference between the measured value and the true value. Metrology is the study of measurement.
There are certain generally used standard measurement systems, such as the English System, the Metric System, and the International System of Units (SI). A metre stick can be used to measure an object's length, a graduated cylinder can be used to measure a liquid's volume, and a thermocouple can be used to measure a fire's temperature. Type, magnitude, unit, and uncertainty are among the parameters that are used to compare the measurements.
Types of Measurement and Units
Standard and non-standard measurements fall under two measurement categories. The value of the standard unit remains constant that cannot be altered with its uniformity in the measurement. In the US, the measurement is expressed in feet, inches, and pounds, but in the metric system, it is expressed in metres, centimetres, and kilograms. The benefits of using a standard unit are as follows:
It facilitates the understanding of measurements in a group of unit systems.
Without the need for conversion, SI units are generated from one another.
A metric system is SI. One of the SI unit's drawbacks is that it only mentions one unit. So, the significance of other units was lessened.
Nonstandard measurement includes the units like a block, an arm, a pencil, etc. that has the benefit of making measurement simpler, but it also has the drawback of being difficult for some people to understand. All the physical quantities must be measured using standard units that are defined by the International System of Units, or SI units. Any physical amount can theoretically be stated in terms of the seven basic units as listed in the table below:
The various measurement types that are utilised to express are listed below:
Time: The units to express time are minutes, hours, days, weeks, months, years, etc.
Length or Distance: Measuring units for length or distance are millimetres, centimetres, kilometres, etc.
Weight: Grams, kilograms, and other units are the weight measuring units of various objects.
Volume: Litres, cm3, and other units are used to express volume.
Temperature: Fahrenheit and centigrade are the two most units used to express the temperature.
In addition to the seven fundamental units, certain units are derived by using one or more base units. These are called derived units such as:
Power: watt (W)
Frequency: hertz (Hz)
Measurement Instruments and Scaling
Different measurement scales are available, including the nominal, ordinal, interval, and ratio scales.
Nominal Measurement
This is the lowest level of scale where the numbers are used to identify or classify the objects by assigning the titles or labels to them. This scaling generally applies to non-numeric variables or inert objects.
Ordinal Measurement
The second level of measurement uses an ordinal measurement scale to arrange the data without indicating how much the data vary from one another. ‘Order’ is symbolised by the ordinal. Ordinal data can be grouped, identified, and rated, sometimes known as qualitative or classified data.
Interval Measurement
The third level of the measurement scale is the interval measurement scale, which is a quantitative measuring scale and allows us to express any two variables' differences.
Ratio Measurement
The fourth level of the measuring scale, which is quantitative, is the ratio measurement scale. The origin, or zero points character, is a special characteristic of ratio scaling.
Uses of Measurement
For the following instances, measurement is a significant concept:
Right dimensions are essential during the design of construction.
For the exchange, purchase, and sale of items.
For food preparations, the materials are commonly taken in particular proportions.
For performing scientific experiments in laboratories.
To finish a particular task, time is an essential issue to consider.
To create medications and treat people.
Interesting Fact
The magnitude of the quantity serves as a standard unit and is used in a variety of measures.
Non-standard units like a digit, handspan, and pace were in use before the discovery of standard units of measurement.
Key Features
An established quantity called a measurement unit is used to represent the physical quantities.
There are numerous systems and units in use for measuring various quantities, including length, area, mass, and volume.
The International System of Units or SI units was established to tackle the problem of different measurement systems, which defines standard units for measurement of all physical quantities.
FAQs on Measurements - A Detailed Summary
1. What is the fundamental concept of measurement in Physics?
In Physics, measurement is the process of comparing an unknown physical quantity with a known, standard quantity of the same nature. It assigns a numerical value and a unit to an object or event's property. For example, to measure the length of a table, we compare it against a standard metre scale.
2. What are the seven fundamental units in the SI system as per the NCERT syllabus?
The International System of Units (SI) defines seven fundamental or base units from which all other units are derived. For the 2025-26 session, students should know:
- Metre (m) for length
- Kilogram (kg) for mass
- Second (s) for time
- Ampere (A) for electric current
- Kelvin (K) for thermodynamic temperature
- Mole (mol) for the amount of substance
- Candela (cd) for luminous intensity
3. What is the main difference between fundamental and derived units? Provide an example.
The main difference lies in their origin. Fundamental units are the basic, independent units for the seven base quantities (like mass, length, time). Derived units, on the other hand, are created by combining these fundamental units through multiplication or division. For example, the unit of speed, metres per second (m/s), is a derived unit because it combines the fundamental units of length (metre) and time (second).
4. Why was it necessary to establish the International System of Units (SI) when other systems already existed?
The SI system was developed to create a single, globally recognised standard for science, technology, and commerce. Before SI, different countries and scientific communities used various systems like MKS (Metre-Kilogram-Second) and CGS (Centimetre-Gram-Second), leading to confusion and complex conversions. The SI system provides a coherent and rational set of units, simplifying international collaboration and preventing errors in data exchange.
5. How do the dimensions of a physical quantity differ from its units?
Dimensions describe the fundamental nature of a physical quantity, irrespective of the measurement system. They are expressed in terms of Mass (M), Length (L), and Time (T). Units are the specific standards used to measure that quantity. For instance, the dimensions of velocity are [L T⁻¹], indicating it is a measure of length per unit time. Its units can be metres per second (m/s), kilometres per hour (km/h), or feet per second (ft/s).
6. What is meant by an 'error' in measurement, and is a perfectly accurate measurement possible?
An 'error' in measurement refers to the uncertainty or the difference between the measured value and the true or actual value of a quantity. Every measurement is subject to some degree of error, which can arise from instrument limitations (systematic error) or unpredictable fluctuations (random error). Therefore, a perfectly accurate measurement with zero error is theoretically impossible to achieve in practice.
7. What is the importance of measurement in real-world applications like engineering and medicine?
Measurement is critical in many fields. In engineering, precise measurements ensure that structures are built to the correct dimensions for safety and functionality. In medicine, accurate measurements of substances are essential for creating effective and safe medications, and vital signs like temperature and blood pressure must be measured correctly for diagnosis and treatment.
8. What are supplementary units in the SI system?
Supplementary units are a special class of dimensionless units used alongside the seven base units in the SI system to describe geometrical quantities. The two supplementary units are:
- The radian (rad) for measuring a plane angle.
- The steradian (sr) for measuring a solid angle.
