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 is the density of a substance relative to some reference substance: Vocabulary. density specific gravity. Specific gravity =. density of substancedensity of reference substance. Specific gravity was defined because it's convenient to have a unitless measure of density.The reference substance for solids and liquids is usually water at 4Â°C. At that temperature, water has a density of 1.0000 g/mL.pecific gravity is the density of a substance relative to some reference substance: Vocabulary. density specific gravity. Specific gravity =. density of substancedensity of reference substance. Specific gravity was defined because it's convenient to have a unitless measure of density.