Question

metre scale of platinum and iridium scale is preserved at 0°c.​ ​
give reason

Answer 1

Answer:

I’m assuming you’re talking about the old standard meter bar kept in France. Like most materials, the metal alloy that the bar was made of expands with increasing temperature. If you want to know the actual length of a meter, you would need to take the length at a specific temperature. The people who created the bar decided that the best temperature would be 0 degrees, though I’m not sure of the logistical or scientific reasons why. By the way, because of the inherent problems of keeping a physical standard (corrosion, thermal expansion/contraction, etc.), the meter, like all units except the kilogram, is now defined as the distance light travels in 1/299792458 of a second in a vacuum. This way it will always be the same, even if the original meter bar is lost.