Need for Measurement of a Physics Quantity

Measurement is a process by which we can weigh or measure any physical quantity of material using equipment and instruments. Measurements of physics quantity can be expressed by a unit known as numerical. By measuring a physics quantity, we can define the property of the material. We can measure mass, weight, and different physical properties like distance, speed, mass, pressure, force, momentum, and energy. Measurement is the system by which we can compare the physical quantity with a unit. When we measure with the help of a formula, it is called indirect measurements. 

Physical quantities.

Every day, we deal with measurements. When we buy vegetables, we ask the vendor to measure the vegetables and pay accordingly. For example, 3kgs cucumber and 500gm coriander; these numbers are associated with measurement. These quantities are known as physical quantities. 

A physical quantity is a property of a material that can be measured. Anything that can be measured in this physical world is called physical quantity. Suppose we calculate the length of a table, where the length is a physical quantity. The mass of any object can be measured, where mass is the physical quantity. There are many physical quantities in this world.

All the physical quantities have two factors, a numerical and a unit, through which we can express the measurement. We study an immense number of phenomena and objects in physics. These can range from the tiny diameter of the atomic nucleus to the universe. The numerical provides much more understanding of physical quantity. 

Since physical quantities can be a minute or extremely large, the unit plays a significant role while writing the expression of the given measurements. Although there are many units, the International System of Units or the SI system was developed to prevent confusion. It would have been tough to measure if an internationally accepted system were absent. For example, measuring the room’s length can be expressed in metres, centimetres, and feet. These units can be converted into each other, and thus, without such a well-defined system, it could be difficult to express the quantity. 

Two forms of fundamental quantity. 

The physical quantity independent of any other physical quantity is called fundamental quantity. The fundamental quantity is also known as the base quantity, and they are used to express other quantities. This quantity can be broken and further used to determine other various physical quantities. Some of the fundamental quantities are:-

• Length
• Time
• Electric current
• Mass
• Temperature
• Luminous intensity
• Amount of substance

The units which are associated with fundamental quantity are known as fundamental units. These are base units that can be achieved from the other units and are defined using the International System of Units. 

The two fundamental units are:-

1. Metre:- Metre is represented by m. It is the fundamental unit of length. The metre is the distance light travels through a vacuum in 1/299792458 seconds. One metre is about 39.37 inches. One metre was early defined as the quantity that is 1650763.73 times the wavelength of a high emitting in a vacuum due to the transition of electrons from 2p10 to 5d5 state in krypton-86. In 1983 the general assembly of weights and measures adopted a new definition of the metre. This definition was expressed in terms of the velocity of light. Presently, metre can be defined as the distance covered by a ray of light in a vacuum during the time duration equal to 1/299792458 per second. 
2. Kilogram:- Kilogram is represented as kg. It is a fundamental unit of electric current. In the early days, 1 kilogram was defined as the mass of the cylinder composed of platinum-iridium alloy maintained by the international bureau of weight and measures. In recent times it has fixed the value of Planck’s constant. 

Different fundamental physical quantities.

The measurement of a material or a particle that can be easily measured is known as fundamental physical quantities. The quantities that can not be measured or calculated physically but can be derived mathematically are known as physical quantities. Many different fundamental physical quantities can be measured using physical fundamentals in physics. Some of the different fundamental physical quantities are as follows:-

• Length 
• Mass
• Temperature 
• Time
• Amount of substance 
• Solid angle
• Plane angle

The last two units are subsidiaries in the SI unit system but are regarded as dimensionless. The current can also be calculated if we know the number of charges that are flowing from the conductor. But it is easy to calculate the current by using an instrument called an ammeter and then counting the number of charges flowing in the circuit. And thus, a current is considered a fundamental physical quantity. 

Conclusion 

Measurement is a process by which we can weigh or measure any physical quantity. Measurement of a physical quantity can be expressed by a unit known as numerical. By measuring a physical quantity, we can define the property of the material. A physical quantity is a property of a material that can be measured. If we measure the room in length, length is a physical quantity. All physical quantities have two factors: numerical and unit. An independent physical quantity, which is independent of any other physical quantity, is called fundamental quantity. The measurement of a material or a particle that can be easily measured is known as fundamental physical quantities.