Yes, OHM is a Scrabble word!

Letter values in Scrabble US: O 1, H 4, M 3.

Is it a valid word?

OHM is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a unit of electrical resistance equal to the resistance between two points on a conductor when a potential difference of one volt between them produces a current of one ampere
German physicist who formulated Ohm's law (1787-1854)

Also: georg simon ohm.