Is it 0.5 ampere or 0.5 amperes? [closed]

It should be "0.5 amperes" and "0.5 hours". It is a rule in English that for any value other than 1, the units should be written in the plural form if they are being spelled out. If you are using abbreviations for units, however, they should remain singular in spelling (e.g. "0.5 A" not "0.5 As").