What is a variable speed drive? A variable speed drive is a piece of equipment that regulates the speed and rotational force, or torque output, of an electric motor. The background and technology. There are millions of motors in use in industry and offices around the world.
The specific gravity for Obsidian is 2.35, it's refractive index is 1.48-1.51, and it's double refraction is None. History Obsidian is named after a Roman, Obsius.
Specific gravity (SG), defined as Ï milk /Ï water, is identified in a similar way, for example, SG2020 or SG420, where the superscript is the temperature at which the milk density was measured, and the subscript the temperature at which the density of water was determined.