What are the 7 units of measurement?
2 Answers
The seven base units of measurement in the International System of Units (SI) are fundamental in defining all other measurements. Here they are:
1. **Meter (m)** - **Length**: The meter is the SI unit for length. It is defined as the distance light travels in a vacuum in \( \frac{1}{299,792,458} \) seconds. It serves as the foundation for measuring distance and dimensions.
2. **Kilogram (kg)** - **Mass**: The kilogram is the SI 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. This unit is essential for measuring the amount of matter in an object.
3. **Second (s)** - **Time**: The second is the SI unit for time. It is defined based on the vibrations of cesium atoms in a cesium atomic clock, specifically as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the cesium-133 atom.
4. **Ampere (A)** - **Electric Current**: The ampere is the SI unit for electric current. It is defined by the flow of electric charge through a conductor, where one ampere is equivalent to one coulomb of charge passing through a point per second.
5. **Kelvin (K)** - **Temperature**: The kelvin is the SI unit for thermodynamic temperature. It is defined based on the Boltzmann constant, with 0 Kelvin being absolute zero (the theoretical point where all molecular motion ceases). One kelvin is the fraction \( \frac{1}{273.16} \) of the thermodynamic temperature of the triple point of water.
6. **Mole (mol)** - **Amount of Substance**: The mole is the SI unit for the amount of substance. It is defined as containing exactly \( 6.02214076 \times 10^{23} \) elementary entities (e.g., atoms, molecules, ions), known as Avogadro's number.
7. **Candela (cd)** - **Luminous Intensity**: The candela is the SI unit for luminous intensity. It is defined based on the light emitted by a source in a specific direction, with a luminous intensity of one candela corresponding to the emission of one lumen per steradian.
These units form the basis for scientific measurement and are used to express all physical quantities. Each of these units can be combined to form derived units for other measurements, such as force (newton), energy (joule), and pressure (pascal).
1. **Meter (m)** - **Length**: The meter is the SI unit for length. It is defined as the distance light travels in a vacuum in \( \frac{1}{299,792,458} \) seconds. It serves as the foundation for measuring distance and dimensions.
2. **Kilogram (kg)** - **Mass**: The kilogram is the SI 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. This unit is essential for measuring the amount of matter in an object.
3. **Second (s)** - **Time**: The second is the SI unit for time. It is defined based on the vibrations of cesium atoms in a cesium atomic clock, specifically as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the cesium-133 atom.
4. **Ampere (A)** - **Electric Current**: The ampere is the SI unit for electric current. It is defined by the flow of electric charge through a conductor, where one ampere is equivalent to one coulomb of charge passing through a point per second.
5. **Kelvin (K)** - **Temperature**: The kelvin is the SI unit for thermodynamic temperature. It is defined based on the Boltzmann constant, with 0 Kelvin being absolute zero (the theoretical point where all molecular motion ceases). One kelvin is the fraction \( \frac{1}{273.16} \) of the thermodynamic temperature of the triple point of water.
6. **Mole (mol)** - **Amount of Substance**: The mole is the SI unit for the amount of substance. It is defined as containing exactly \( 6.02214076 \times 10^{23} \) elementary entities (e.g., atoms, molecules, ions), known as Avogadro's number.
7. **Candela (cd)** - **Luminous Intensity**: The candela is the SI unit for luminous intensity. It is defined based on the light emitted by a source in a specific direction, with a luminous intensity of one candela corresponding to the emission of one lumen per steradian.
These units form the basis for scientific measurement and are used to express all physical quantities. Each of these units can be combined to form derived units for other measurements, such as force (newton), energy (joule), and pressure (pascal).
The seven fundamental units of measurement, as defined by the International System of Units (SI), are:
1. **Meter (m)** – **Length**
- The meter is the base unit for measuring length or distance. It is defined as the distance light travels in a vacuum in \( \frac{1}{299,792,458} \) of a second.
2. **Kilogram (kg)** – **Mass**
- The kilogram is the base unit for measuring mass. It is defined by the mass of the International Prototype of the Kilogram, a platinum-iridium cylinder kept at the International Bureau of Weights and Measures.
3. **Second (s)** – **Time**
- The second is the base unit for measuring time. It is defined as the duration of 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)** – **Electric Current**
- The ampere is the base unit for measuring electric current. It is defined by the constant current that, if maintained in two straight parallel conductors of infinite length and negligible cross-section, would produce a force between them of \(2 \times 10^{-7}\) newtons per meter of length.
5. **Kelvin (K)** – **Temperature**
- The kelvin is the base unit for measuring thermodynamic temperature. It is defined by setting the fixed numerical value of the Boltzmann constant to \(1.380649 \times 10^{-23}\) when expressed in the unit \(J \cdot K^{-1}\) (joules per kelvin).
6. **Mole (mol)** – **Amount of Substance**
- The mole is the base unit for measuring 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)** – **Luminous Intensity**
- The candela is the base unit for measuring luminous intensity. It is defined as the luminous intensity in a given direction of a source that emits monochromatic radiation of frequency \(5.4 \times 10^{14}\) Hz and that has a radiant intensity in that direction of \(1/683\) watt per steradian.
These units are the foundation of the SI system and are used worldwide to provide consistent and accurate measurements in science, industry, and everyday life.
1. **Meter (m)** – **Length**
- The meter is the base unit for measuring length or distance. It is defined as the distance light travels in a vacuum in \( \frac{1}{299,792,458} \) of a second.
2. **Kilogram (kg)** – **Mass**
- The kilogram is the base unit for measuring mass. It is defined by the mass of the International Prototype of the Kilogram, a platinum-iridium cylinder kept at the International Bureau of Weights and Measures.
3. **Second (s)** – **Time**
- The second is the base unit for measuring time. It is defined as the duration of 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)** – **Electric Current**
- The ampere is the base unit for measuring electric current. It is defined by the constant current that, if maintained in two straight parallel conductors of infinite length and negligible cross-section, would produce a force between them of \(2 \times 10^{-7}\) newtons per meter of length.
5. **Kelvin (K)** – **Temperature**
- The kelvin is the base unit for measuring thermodynamic temperature. It is defined by setting the fixed numerical value of the Boltzmann constant to \(1.380649 \times 10^{-23}\) when expressed in the unit \(J \cdot K^{-1}\) (joules per kelvin).
6. **Mole (mol)** – **Amount of Substance**
- The mole is the base unit for measuring 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)** – **Luminous Intensity**
- The candela is the base unit for measuring luminous intensity. It is defined as the luminous intensity in a given direction of a source that emits monochromatic radiation of frequency \(5.4 \times 10^{14}\) Hz and that has a radiant intensity in that direction of \(1/683\) watt per steradian.
These units are the foundation of the SI system and are used worldwide to provide consistent and accurate measurements in science, industry, and everyday life.