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 (sometimes referred to as Density) is a useful diagnostic attribute when trying to determine the mineral species of an unknown mineral specimen. But textbooks usually describe testing specific gravity using a laboratory balance scale that few of us have in our homes.