What are the 7 main SI units?
2 Answers
The seven main SI (International System of Units) units are:
1. **Meter (m)** - unit of length
2. **Kilogram (kg)** - unit of mass
3. **Second (s)** - unit of time
4. **Ampere (A)** - unit of electric current
5. **Kelvin (K)** - unit of temperature
6. **Mole (mol)** - unit of amount of substance
7. **Candela (cd)** - unit of luminous intensity
These units form the foundation for measuring various physical quantities.
1. **Meter (m)** - unit of length
2. **Kilogram (kg)** - unit of mass
3. **Second (s)** - unit of time
4. **Ampere (A)** - unit of electric current
5. **Kelvin (K)** - unit of temperature
6. **Mole (mol)** - unit of amount of substance
7. **Candela (cd)** - unit of luminous intensity
These units form the foundation for measuring various physical quantities.
The seven main SI (International System of Units) base units form the foundation of the metric system. Each unit corresponds to a fundamental physical quantity. Here they are:
1. **Meter (m)** - **Unit of Length**
The meter is the base unit for measuring length. It is defined as the distance traveled by light in a vacuum in \(1/299,792,458\) of a second.
2. **Kilogram (kg)** - **Unit of Mass**
The kilogram is the base unit for mass. It is defined as the mass of the International Prototype of the Kilogram, a platinum-iridium cylinder kept at the International Bureau of Weights and Measures (BIPM).
3. **Second (s)** - **Unit of Time**
The second is the base unit for time. It is defined based on the radiation period of the cesium-133 atom, specifically \(9,192,631,770\) periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.
4. **Ampere (A)** - **Unit of Electric Current**
The ampere is the base unit for electric current. It is defined as the constant current which, if maintained in two straight parallel conductors of infinite length, of negligible cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to \(2 \times 10^{-7}\) newtons per meter of length.
5. **Kelvin (K)** - **Unit of Thermodynamic Temperature**
The kelvin is the base unit for thermodynamic temperature. It is defined as the fraction \(1/273.16\) of the thermodynamic temperature of the triple point of water.
6. **Mole (mol)** - **Unit of Amount of Substance**
The mole is the base unit for the amount of substance. It is defined as the amount of substance that contains as many elementary entities (such as atoms, molecules, ions, etc.) as there are in \(0.012\) kilograms of carbon-12.
7. **Candela (cd)** - **Unit of Luminous Intensity**
The candela is the base unit for luminous intensity. It is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency \(540 \times 10^{12}\) hertz and that has a radiant intensity in that direction of \(1/683\) watt per steradian.
These base units are used to derive other units of measure, making them fundamental to scientific and engineering disciplines.
1. **Meter (m)** - **Unit of Length**
The meter is the base unit for measuring length. It is defined as the distance traveled by light in a vacuum in \(1/299,792,458\) of a second.
2. **Kilogram (kg)** - **Unit of Mass**
The kilogram is the base unit for mass. It is defined as the mass of the International Prototype of the Kilogram, a platinum-iridium cylinder kept at the International Bureau of Weights and Measures (BIPM).
3. **Second (s)** - **Unit of Time**
The second is the base unit for time. It is defined based on the radiation period of the cesium-133 atom, specifically \(9,192,631,770\) periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.
4. **Ampere (A)** - **Unit of Electric Current**
The ampere is the base unit for electric current. It is defined as the constant current which, if maintained in two straight parallel conductors of infinite length, of negligible cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to \(2 \times 10^{-7}\) newtons per meter of length.
5. **Kelvin (K)** - **Unit of Thermodynamic Temperature**
The kelvin is the base unit for thermodynamic temperature. It is defined as the fraction \(1/273.16\) of the thermodynamic temperature of the triple point of water.
6. **Mole (mol)** - **Unit of Amount of Substance**
The mole is the base unit for the amount of substance. It is defined as the amount of substance that contains as many elementary entities (such as atoms, molecules, ions, etc.) as there are in \(0.012\) kilograms of carbon-12.
7. **Candela (cd)** - **Unit of Luminous Intensity**
The candela is the base unit for luminous intensity. It is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency \(540 \times 10^{12}\) hertz and that has a radiant intensity in that direction of \(1/683\) watt per steradian.
These base units are used to derive other units of measure, making them fundamental to scientific and engineering disciplines.