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The International System of Units (SI) is primarily known by its English abbreviation, 'ISU'.
Answer: False
Explanation: The source states the international abbreviation is SI, derived from its French name, Système international d'unités.
The SI system holds official status in only a few select countries, primarily those involved in scientific research.
Answer: False
Explanation: The SI system holds official status in nearly every country, making it a global standard for science, technology, industry, and commerce.
The International Bureau of Weights and Measures, abbreviated BIPM, is responsible for coordinating the SI system.
Answer: True
Explanation: The source confirms that the International Bureau of Weights and Measures (BIPM) coordinates the SI system, working alongside the CGPM and CIPM.
An official SI diagram illustrates derived units in the outer ring and base units in the inner ring.
Answer: False
Explanation: The source material describes a diagram where the SI base units are in the outer ring and the SI defining constants are in the inner ring.
The General Conference on Weights and Measures (CGPM) was established by the Metre Convention of 1875 to define and standardize a new measurement system.
Answer: True
Explanation: The source states that the General Conference on Weights and Measures (CGPM) was established by the Metre Convention of 1875 to define and standardize a new measurement system.
The International System of Quantities (ISQ) defines the physical quantities that are measured using SI units.
Answer: True
Explanation: The source states that the International System of Quantities (ISQ) defines the physical quantities and equations that provide the context for the SI units.
The SI system is regulated by a single international organization, the BIPM.
Answer: False
Explanation: The SI system is regulated by three international organizations: the General Conference on Weights and Measures (CGPM), the International Committee for Weights and Measures (CIPM), and the International Bureau of Weights and Measures (BIPM).
The 'SI Brochure' is a document published by the ISO that collects all decisions and recommendations concerning SI units.
Answer: False
Explanation: The 'SI Brochure' is published by the BIPM (International Bureau of Weights and Measures), not the ISO (International Organization for Standardization).
What is the international abbreviation for the International System of Units?
Answer: SI
Explanation: The source material identifies the international abbreviation for the Système international d'unités as SI.
In which sectors is the SI system primarily employed?
Answer: Science, technology, industry, and everyday commerce
Explanation: The source states that the SI system is employed broadly in science, technology, industry, and everyday commerce, with official status in nearly every country.
Which organization coordinates the SI system?
Answer: The International Bureau of Weights and Measures (BIPM)
Explanation: The source identifies the International Bureau of Weights and Measures (BIPM) as the organization that coordinates the SI system.
According to the diagram mentioned in the source, what is depicted in the inner ring of the SI system illustration?
Answer: SI defining constants
Explanation: The source describes a diagram where the SI defining constants are depicted in the inner ring, with the base units in the outer ring.
What does the International System of Quantities (ISQ) define?
Answer: The quantities and equations that provide the context for defining SI units
Explanation: The ISQ defines the physical quantities and the equations relating them, which provides the necessary context for the definitions of the SI units used to measure them.
Which international body is responsible for publishing the 'SI Brochure'?
Answer: The International Bureau of Weights and Measures (BIPM)
Explanation: The source specifies that the 'SI Brochure', which contains all decisions and recommendations on SI units, is published by the BIPM.
The SI system consists of nine base units that can be combined to form coherent derived units.
Answer: False
Explanation: The SI system is comprised of seven, not nine, base units.
The kilogram (kg) is the SI base unit for mass, and the candela (cd) is the SI base unit for luminous intensity.
Answer: True
Explanation: The source lists the kilogram (kg) as the base unit for mass and the candela (cd) as the base unit for luminous intensity among the seven SI base units.
The International System of Units is fundamentally defined by a set of seven defining constants, each with a specific exact numerical value.
Answer: True
Explanation: The source confirms that the SI is defined by a set of seven defining constants, whose numerical values are fixed exactly when expressed in their corresponding SI units.
The magnitudes of all SI units are defined by declaring that the seven defining constants have approximate numerical values.
Answer: False
Explanation: The magnitudes of all SI units are defined by declaring that the seven defining constants have specific *exact* numerical values, not approximate ones.
The second is defined based on the radiation corresponding to the transition between hyperfine levels of the caesium-133 atom.
Answer: True
Explanation: The source defines the second as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.
The metre is defined as the distance travelled by sound in vacuum in a specific fraction of a second.
Answer: False
Explanation: The metre is defined as the distance travelled by *light* in vacuum, not sound.
The kilogram is defined by setting the Planck constant to a specific value, given the definitions of the metre and the second.
Answer: True
Explanation: The source states that the kilogram is defined by fixing the Planck constant (h) to an exact numerical value, in conjunction with the definitions of the metre and second.
The ampere is defined based on the flow of a specific number of elementary charges per minute.
Answer: False
Explanation: The ampere is defined based on the flow of a specific number of elementary charges per *second*, not per minute.
The kelvin is defined by setting the fixed numerical value of the Avogadro constant.
Answer: False
Explanation: The kelvin is defined by setting the fixed numerical value of the *Boltzmann* constant, not the Avogadro constant.
When the mole is used, the elementary entities must be specified, such as atoms or molecules.
Answer: True
Explanation: The source explicitly states that when the mole is used, the elementary entities (e.g., atoms, molecules, ions) must be specified.
The candela is defined based on a source emitting monochromatic radiation of frequency 5.4 x 10¹² hertz.
Answer: False
Explanation: The candela is defined based on a source emitting monochromatic radiation of frequency 5.4 x 10¹⁴ hertz, not 5.4 x 10¹² hertz.
How many base units does the SI system comprise?
Answer: Seven
Explanation: The source consistently states that the SI system comprises seven base units.
Which of the following is the SI base unit for thermodynamic temperature?
Answer: Kelvin (K)
Explanation: The source identifies the kelvin (K) as the SI base unit for thermodynamic temperature.
Which of the following is NOT one of the seven SI defining constants?
Answer: The gravitational constant (G)
Explanation: The source lists the seven defining constants, which include the speed of light, the Planck constant, and the Avogadro constant, but not the gravitational constant.
How is the metre defined in the SI system?
Answer: As the distance travelled by light in vacuum in 1/299,792,458 of a second
Explanation: The definition of the metre is based on fixing the speed of light in vacuum (c) to 299,792,458 m/s, which means a metre is the distance light travels in vacuum in 1/299,792,458 of a second.
What is the definition of the ampere (A) in the SI system?
Answer: The flow of 1 / (1.602176634 × 10⁻¹⁹) times the elementary charge per second
Explanation: The ampere is defined by fixing the elementary charge (e) to 1.602176634 × 10⁻¹⁹ C. An ampere is an electric current of 1 coulomb per second, which corresponds to the flow of 1/e elementary charges per second.
What must be specified when the mole is used as an SI unit?
Answer: The elementary entities being referred to
Explanation: The source explicitly states that when the mole is used, the elementary entities (such as atoms, molecules, or ions) must be specified.
The SI system offers twenty-four prefixes to create non-coherent SI units that are always decimal multiples or sub-multiples of a coherent unit.
Answer: True
Explanation: The source confirms that the SI system provides twenty-four prefixes to form decimal multiples and sub-multiples, creating convenient non-coherent units for various applications.
A coherent derived unit is an SI unit that can be represented as a product of powers of the base units with a numerical multiplier of one.
Answer: True
Explanation: This is the correct definition of a coherent derived unit as provided in the source material, with metre per second (m/s) given as an example.
Only ten coherent derived units have been given special names and symbols in the SI system.
Answer: False
Explanation: The source states that twenty-two, not ten, coherent derived units have been given special names and symbols.
Metric prefixes are used to create units that are decimal multiples or sub-multiples for the same physical quantity.
Answer: True
Explanation: The source confirms that metric prefixes systematically create units that are decimal (power-of-ten) multiples or sub-multiples of a coherent unit.
In a compound unit like g/cm³, the prefix 'c' in 'cm³' applies to the entire cubic metre.
Answer: False
Explanation: In a compound unit, the prefix applies only to the unit it is attached to. Therefore, cm³ is interpreted as (cm)³, or cubic centimetre, not centi-cubic-metre.
Multiples and sub-multiples of mass are named as if the gram were the base unit, despite the kilogram being the coherent base unit.
Answer: True
Explanation: Due to the historical nature of the kilogram having a prefix in its name, the source confirms that prefixes for mass are attached to 'gram' (e.g., milligram) rather than 'kilogram'.
According to the SI Brochure, unit names should always start with a capital letter to signify their importance.
Answer: False
Explanation: The SI Brochure specifies that unit names should be treated as common nouns and typically start with a lowercase letter, unless grammar dictates otherwise (e.g., at the start of a sentence).
US English uses 'metre' and 'litre', while International English uses 'meter' and 'liter'.
Answer: False
Explanation: The spelling is reversed: US English uses 'meter' and 'liter', while International English uses 'metre' and 'litre'.
Unit name variations like 'watt-peak' are acceptable in the SI system to provide additional context.
Answer: False
Explanation: Such variations are unacceptable because the SI mandates that information about the physical quantity must be presented separately and not mixed with the unit name.
The 2022 adoption of new metric prefixes extended the range of SI prefixes to cover decimal powers from 10⁻³⁰ to 10³⁰.
Answer: True
Explanation: The source confirms that in 2022, new prefixes including 'quetta' (10³⁰) and 'quecto' (10⁻³⁰) were adopted, extending the range of available prefixes.
Which of the following is an example of a coherent derived unit?
Answer: Metre per second (m/s)
Explanation: The kilogram, second, and candela are base units. The metre per second is a coherent derived unit, formed as a product of powers of base units with a multiplier of one.
How many coherent derived units have been given special names and symbols in the SI system?
Answer: Twenty-two
Explanation: The source states that twenty-two coherent derived units, such as the hertz, newton, and joule, have been given special names and symbols.
What is the rule for forming multiples and sub-multiples of mass in the SI system?
Answer: Multiples and sub-multiples are named as if the gram were the base unit
Explanation: Due to the historical anomaly of the base unit 'kilogram' containing a prefix, the rule is that prefixes are attached to 'gram' (e.g., milligram, mg) instead.
According to the SI Brochure, how should unit names generally be typeset in written text?
Answer: As common nouns, typically starting with a lowercase letter
Explanation: The SI Brochure specifies that unit names are treated as common nouns and should be typeset in the same style as surrounding text, usually starting with a lowercase letter.
What is the US English spelling for the SI unit of length?
Answer: Meter
Explanation: The source indicates that US English uses the spelling 'meter', while International English uses 'metre'.
What was the significance of the 2022 adoption of new metric prefixes by the BIPM?
Answer: It extended the range of SI prefixes to cover decimal powers from 10⁻³⁰ to 10³⁰
Explanation: The 2022 adoption of prefixes like 'quetta' (10³⁰) and 'quecto' (10⁻³⁰) extended the available range of decimal powers for forming SI units.
The primary motivation for the SI system was to standardize units across different countries, not to resolve inconsistencies within existing systems.
Answer: False
Explanation: The original motivation was to address the diversity and inconsistencies that had emerged within the centimetre-gram-second (CGS) systems of units.
The SI system was published in 1960 and was based on the centimetre-gram-second (CGS) system.
Answer: False
Explanation: The SI system, published in 1960, was based on the metre-kilogram-second (MKS) system of units, not the CGS system.
The CGS system formalized the concept of a 'coherent' system of units where base units combine to define derived units without extra factors.
Answer: True
Explanation: The source credits the CGS (centimetre-gram-second) system with formalizing the concept of a 'coherent' system of units.
Giovanni Giorgi resolved the difficulty of expressing electrical units by advocating for a fifth base unit.
Answer: False
Explanation: Giovanni Giorgi advocated for a *fourth* base unit for an electrical quantity to be added to the existing three base units of length, mass, and time.
The MKSA system was approved in 1946 after electric current, with the unit 'ampere', was chosen as the fourth base unit.
Answer: True
Explanation: The source confirms that electric current (ampere) was chosen as the fourth base unit, leading to the MKSA (metre-kilogram-second-ampere) system, which was approved in 1946.
The 10th CGPM in 1954 defined an international system that included five base units.
Answer: False
Explanation: The 10th CGPM in 1954 defined an international system with six base units: metre, kilogram, second, ampere, degree Kelvin, and candela.
The mole was added as the seventh base unit to the SI system in 1971.
Answer: True
Explanation: The source states that after the SI was formally adopted in 1960, the mole was added as the seventh base unit in 1971.
The International Prototype of the Kilogram (IPK) was problematic because its mass was observed to be increasing over time.
Answer: False
Explanation: The problem with the IPK was the observed divergence in mass between it and its official copies, indicating an inherent instability, not a consistent increase in its own mass.
After the 2019 redefinition, the SI is defined by fixing the numerical values of seven defining constants.
Answer: True
Explanation: The source confirms that the 2019 redefinition established that the SI is defined by fixing the numerical values of seven fundamental defining constants.
The distinction between base units and derived units was abolished after the 2019 SI redefinition.
Answer: False
Explanation: The distinction between base and derived units was retained because it is considered useful, historically well-established, and corresponds to the standards for the International System of Quantities (ISQ).
What was the primary motivation behind the development of the SI system?
Answer: To address the diversity and inconsistencies within the centimetre-gram-second (CGS) systems
Explanation: The source states that the original motivation for the SI was to resolve the diversity and inconsistencies of units that had emerged within the CGS systems.
When was the SI system formally published?
Answer: 1960
Explanation: The source specifies that the SI system was formally adopted and published by the 11th CGPM in 1960.
What principle did the CGS (centimetre-gram-second) system formalize?
Answer: The concept of a 'coherent' system of units
Explanation: The source credits the CGS system with formalizing the concept of a 'coherent' system, where derived units are formed from base units without extra numerical factors.
When was the mole added as the seventh base unit to the SI system?
Answer: 1971
Explanation: The source states that the mole was added as the seventh base unit in 1971, after the initial adoption of the SI in 1960.
What was the primary issue with the International Prototype of the Kilogram (IPK) that led to the 2019 redefinition of the SI?
Answer: It was the only physical artifact defining a base unit and showed instability compared to its copies
Explanation: The key problem was the observed mass divergence between the IPK and its copies, indicating an instability in the physical artifact that undermined the precision of the entire system.
What was the fundamental change in how the SI system is defined after the 2019 redefinition?
Answer: It is defined by fixing the numerical values of seven defining constants
Explanation: The 2019 redefinition shifted the SI's foundation from a set of base units (some tied to artifacts) to a system where all units are constructed from seven fundamental constants with fixed numerical values.
Why is the distinction between base units and derived units still maintained in the SI system after the 2019 redefinition?
Answer: It is considered useful, historically well-established, and corresponds to the ISQ standards
Explanation: Despite all units now being derivable from constants, the base/derived distinction is retained for its utility, historical continuity, and alignment with the International System of Quantities (ISQ).
The coherent SI unit for density is kilogram per cubic metre (kg/m³).
Answer: True
Explanation: The source lists kilogram per cubic metre (kg/m³) as the coherent SI unit for both density and mass concentration.
The coherent SI unit for energy, work, or amount of heat is the watt (W).
Answer: False
Explanation: The coherent SI unit for energy, work, or amount of heat is the joule (J). The watt (W) is the unit for power.
What is the coherent SI unit for electric charge?
Answer: Coulomb (C)
Explanation: The source identifies the coulomb (C) as the coherent SI unit for electric charge.
Which of the following is the coherent SI unit for pressure or stress?
Answer: Pascal (Pa)
Explanation: The source identifies the pascal (Pa) as the coherent SI unit for pressure or stress.
What is the coherent SI unit for electrical resistance?
Answer: Ohm (Ω)
Explanation: The source identifies the ohm (Ω) as the coherent SI unit for electrical resistance.
What is the coherent SI unit for magnetic flux density?
Answer: Tesla (T)
Explanation: The source identifies the tesla (T) as the coherent SI unit for magnetic flux density.
What is the coherent SI unit for Celsius temperature?
Answer: Degree Celsius (°C)
Explanation: The source identifies the degree Celsius (°C) as the coherent SI unit for Celsius temperature, which is directly related to the base unit kelvin.
What is the coherent SI unit for absorbed dose or kerma?
Answer: Gray (Gy)
Explanation: The source identifies the gray (Gy) as the coherent SI unit for absorbed dose or kerma.
What is the coherent SI unit for volume?
Answer: Cubic metre (m³)
Explanation: The source identifies the cubic metre (m³) as the coherent SI unit for volume.
What is the coherent SI unit for current density?
Answer: Ampere per square metre (A/m²)
Explanation: The source identifies the ampere per square metre (A/m²) as the coherent SI unit for current density.
What is the coherent SI unit for dynamic viscosity?
Answer: Pascal-second (Pa·s)
Explanation: The source identifies the pascal-second (Pa·s) as the coherent SI unit for dynamic viscosity.
What is the coherent SI unit for thermal conductivity?
Answer: Watt per metre-kelvin (W/(m·K))
Explanation: The source identifies the watt per metre-kelvin (W/(m·K)) as the coherent SI unit for thermal conductivity.
What is the coherent SI unit for permittivity?
Answer: Farad per metre (F/m)
Explanation: The source identifies the farad per metre (F/m) as the coherent SI unit for permittivity.
The 'realisation' of an SI unit is the practical procedure for determining its value, distinct from its fundamental definition.
Answer: True
Explanation: The source distinguishes between the fundamental 'definition' of a unit (based on a constant) and its 'realisation' (the practical procedure to measure it).
The BIPM publishes 'mises en pratique' documents that describe the historical origins of SI units.
Answer: False
Explanation: 'Mises en pratique' documents describe the current best practical methods for *realizing* a unit's definition, not its historical origins.
One hectare is equivalent to 1000 square metres in SI units.
Answer: False
Explanation: One hectare (ha) is equivalent to 10,000 square metres (m²).
What is the purpose of 'mises en pratique' documents published by the BIPM?
Answer: To describe the current best practical methods for realizing SI unit definitions
Explanation: The source states that 'mises en pratique' (putting into practice) documents describe the current best practical methods for realizing a unit's definition.
Which of the following non-SI units is accepted for use with the SI system?
Answer: Litre
Explanation: The source lists the litre, along with units like the minute, hour, and tonne, as a non-SI unit accepted for use with the SI due to its widespread use.
What is the SI equivalent of one day (d)?
Answer: 86,400 seconds
Explanation: One day is defined as 24 hours, and since one hour is 3600 seconds, one day is equivalent to 24 x 3600 = 86,400 seconds.
How is one degree of angle (°) expressed in radians (rad), the SI derived unit for plane angle?
Answer: (π / 180) radians
Explanation: The source provides the conversion factor for one degree of angle as (π / 180) radians.
What is the SI equivalent of one tonne (t)?
Answer: 1 megagram (Mg)
Explanation: One tonne (t) is defined as 1000 kilograms (kg). Since 'mega' is the prefix for 10⁶, and a gram is 10⁻³ kg, 1000 kg is equal to 1 megagram (Mg).