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.
Solids and Metals-Specific Gravities. The Specific Gravity-SG-is a dimensionless unit defined as the ratio of density of the material to the density of water at a specified temperature. It is common to use the density of water at 4 oC (39 oF) as reference-at this point the density of water is at the highest.