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Guidelines for Examination

 
 

3. Units used with the SI, and whose values in SI are obtained experimentally

The unified atomic mass unit is 1/12 of the mass of an atom of the nuclide 12C.

The electronvolt is the kinetic energy acquired by an electron passing through a potential difference of 1 volt in a vacuum.

Quantity

Unit

 

 

 

Name

Symbol

Value

Mass

unified atomic mass unit

U

1 u ≈ 1,6605655 x 10-27 kg

Energy

electronvolt

eV

1eV ≈ 1,6021892 x 10-19 J

 

The value of these units, expressed in SI units, is not known exactly.

The prefixes and their symbols listed in F‑II, Annex 21.3 may be used in conjunction with these two units and with their symbols.