## Specific gravity

The specific gravity of a substance is the ratio of the substance’s density to the density of water. The density of water is 1 gram per cubic centimeter (1 g/cm3), so the specific gravity of a substance is simply its density in grams per cubic centimeter divided by 1. For example, the density of gold … Read more

## Permeability of free space (a vacuum)

The permeability of free space (a vacuum) is a measure of the ease with which a magnetic field can penetrate a material. It is a ratio of the magnetic flux density (B) to the magnetic field strength (H). The SI unit of permeability is the henry per meter (H/m). The permeability of free space is … Read more

## Candela (cd)

The candela is the SI unit of luminous intensity, or the power emitted by a light source in a particular direction. It is equal to one lumen per steradian. The candela is often used to measure the brightness of light sources, such as lamps and LEDs. It is also used in photometry, for measuring the … Read more

## Siemens (mho)

The Siemens (mho) is the unit of electrical conductance. It is the reciprocal of electrical resistance and is represented by the symbol “S”. One Siemens is equal to one ampere per volt. What has a unit of mho? A mho is a unit of electrical conductance. It is the reciprocal of an ohm, and is … Read more

## Radiant intensity

Radiant intensity is a measure of the power of electromagnetic radiation per unit area. It is a measure of the intensity of radiation from a point source in a particular direction. Radiant intensity is usually measured in watts per square metre (W/m2). How do you calculate radiant intensity? Radiant intensity is a measure of the … Read more

## Gravitational constant

The gravitational constant is an empirical physical constant involved in the calculation of the force of gravity, particularly its inverse-square law. In SI units, the gravitational constant is equal to 6.674×10-11 m3 kg-1 s-2. The gravitational constant is denoted by the letter G. The gravitational constant is a key parameter in the mathematical description of … Read more

## InterNIC (Internet Network Information Center)

The InterNIC is a non-profit organization that was created to provide internet-related information and services to the public. It is responsible for managing the .com, .net, and .org domains, as well as providing other services such as Whois and DNS. Who owns InterNIC? InterNIC is owned by ICANN, which is a nonprofit organization. What is … Read more