milligrams
Explanation:
The best unit to measure the mass of a grain of salt is the milligram.
This is about; a thousandth of a gram.
A grain of salt is a very small particle size that can still be visible with the eye.
It has a very low and small mass.
For substances like this, we use the milligram:
1000milligram = 1g
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Explanation:
this is a physical property
Answer:
b. 
Explanation:
As we know that the electric field due to infinite line charge is given as

here we can find potential difference between two points using the relation

now we have

now we have

now plug in all values in it


now we know by energy conservation


The answer is: Salt! :)
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