Yes, COULOMBS is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, U 1, L 1, O 1, M 3, B 3, S 1.

Is it a valid word?

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

a unit of electrical charge equal to the amount of charge transferred by a current of 1 ampere in 1 second
French physicist famous for his discoveries in the field of electricity and magnetism; formulated Coulomb's Law (1736-1806)

Also: c, ampere-second, charles augustin de coulomb.