18 Questions
Which of the following is NOT a base unit in the SI system?
Radian
What is the unit for plane angle in the SI system?
Radian
Which of these systems of units had the base units of foot, pound, and second?
FPS
What is the full form of the abbreviation 'SI'?
Système Internationale d' Unites
Which organization is responsible for developing and revising the SI system?
Bureau International des Poids et Measures (BIPM)
What is the SI unit for solid angle?
Steradian
What is the internationally accepted reference standard called?
Unit
Which system of units was not extensively used by scientists in earlier times?
SI system
What is the term used for units obtained for physical quantities other than base quantities?
Derived units
How are the units for derived quantities related to the base units?
They are expressed as combinations of base units
What do we need for expressing all physical quantities, even though their number appears large?
A limited number of units
Which term is used to refer to the complete set of both base and derived units?
System of units
What is the SI unit for plane angle?
Radian (rad)
Which of the following is a dimensionless quantity?
Both plane angle and solid angle
The SI unit for solid angle is:
Steradian (sr)
Which of the following is the SI base unit for length?
Metre (m)
Which of the following is NOT an SI base unit?
Radian
The SI base unit for time is defined in terms of:
The caesium-133 atom hyperfine transition frequency
Study Notes
Units and Measurement
- Plane angle is measured in radians (rad) and solid angle is measured in steradians (sr), both of which are dimensionless quantities.
SI Base Quantities and Units
- The SI unit of length is the metre (m), defined by the fixed numerical value of the speed of light in vacuum.
- The SI unit of mass is the kilogram (kg), defined by the fixed numerical value of the Planck constant.
- The SI unit of time is the second (s), defined by the fixed numerical value of the caesium frequency.
- The SI unit of electric current is the ampere (A), defined by the fixed numerical value of the elementary charge.
Historical Systems of Units
- The CGS system had centimetre, gram, and second as its base units.
- The FPS system had foot, pound, and second as its base units.
- The MKS system had metre, kilogram, and second as its base units.
International System of Units (SI)
- The SI system was developed by the Bureau International des Poids et Mesures (BIPM) in 1971 and revised in 2018.
- The SI system is internationally accepted and used in scientific, technical, industrial, and commercial work.
- There are seven base units in the SI system.
Units and Measurement
- A unit is a standard reference used to express the measurement of a physical quantity.
- A measurement result is expressed by a number accompanied by a unit.
- Base units are used to express fundamental or base quantities.
- Derived units are obtained by combining base units to express derived quantities.
- A complete set of base units and derived units is known as a system of units.
This quiz covers the units for plane angle and solid angle, which are radian (rad) and steradian (sr) respectively. Both of these units are dimensionless quantities. The quiz also includes descriptions of plane angle (dθ) and solid angle (dΩ), along with SI base quantities and units.
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