Multiple choice general knowledge math & puzzles The unit of energy in MKS system is Volt Erg Ohm Joule Reveal answer Fill a bubble to check yourself D Correct answer Explanation In the MKS (meter-kilogram-second) system, the unit of energy is the Joule. Volt is for potential difference, Ohm is for resistance, and Erg is the unit of energy in the CGS (centimeter-gram-second) system, not MKS.