Kilogram has New defination

Background:   After 130 years The Definition of Kilogram has changed. On the day of “World Metrology Day” The General Conference on Weights and Measures organised by  “International Bureau of Weights and Measures” (BPIN) which was held at Paris, France adopt the resolution to redefined the Four out of Seven Base units such as Kilogram, Kelvin, Mole and Ampere. The proposal was agreed by 60 Countries to assure the future stability of the SI and open the opportunity for the use of new technologies, including quantum technologies, to implement the definitions. 

1. Why such changes needed ?

Ans: "Using the fundamental constants we observe in nature as a foundation for important concepts, such as mass and time, means that we have a stable foundation from which to advance our scientific understanding, develop new technologies and address some of society's greatest challenges," said Martin Milton, Director, International Bureau of Weights and Measures (BIPM). 

2. What will happen ?

Ans: The unit of Kilogram joined a bunch of other units such as second, metre, ampere, kelvin, mole and candela that will no longer be compared with physical objects as standards of reference. The change comes after nearly 130 years. In 1889 a platinum-iridium cylinder was used to define how much mass one kilogram represented. Now, a more abstract definition of the kilogram has been adopted in terms of fundamental constants, namely, the Planck’s constant H.

3. Historical Prospect:

The definition of the kilogram for more than 130 years old since 1889  the International Prototype of the Kilogram (IPK), also called “Le Grand K” a cylinder of a platinum alloy stored at the International Bureau of Weights and Measures (BIPM) in France, will now be retired and It will be replaced by the Planck constant -- the fundamental constant of quantum physics. While the stability of the IPK could only be confirmed by comparisons with identical copies, a difficult and potentially inaccurate process, the Planck constant is ready for use everywhere and always. 

4. What is Kibble Balance and how it measure ?

Ans: Bryan Kibble at the U.K.’s National Physical Laboratory (NPL), who conceptualized it in 1975, the Kibble balance is an exquisitely accurate weighing machine. Like any balance, it is designed to equalize one force with another: In this case, the weight of a test mass is exactly offset by a force produced when an electrical current is run through a coil of wire immersed in a surrounding magnetic field. The surrounding field is provided by a large permanent magnet system or an electromagnet. The moveable coil, once electrified, becomes an electromagnet with a field strength proportional to the amount of current it conducts. When the coil's field interacts with the surrounding magnetic field, an upward force is exerted on the coil. The magnitude of that force is controlled by adjusting the current.