SI Units Practice Questions
20 free SI Units practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following is one of the seven fundamental base units in the International System of Units (SI)?
- A Newton
- B Joule
- C Kelvin
- D Watt
Correct answer: Kelvin
The Kelvin is the SI base unit for thermodynamic temperature. The other options provided—Newton, Joule, and Watt—are derived units based on combinations of the fundamental units.
The SI unit 'Candela' is used to measure which physical quantity?
- A Luminous intensity
- B Magnetic flux
- C Electric charge
- D Amount of substance
Correct answer: Luminous intensity
The candela measures the luminous intensity in a given direction of a light source. it is a base unit that describes the power emitted by a light source in a particular beam.
Which derived SI unit is used to express pressure or stress?
- A Tesla
- B Pascal
- C Henry
- D Weber
Correct answer: Pascal
The Pascal (Pa) is the SI unit for pressure, defined as one Newton per square meter. It is named after the French mathematician and physicist Blaise Pascal.
In the SI system, the 'Mole' is defined as the unit for which of the following?
- A Mass of an atom
- B Density of a liquid
- C Amount of substance
- D Molecular weight
Correct answer: Amount of substance
The mole is the SI base unit for the amount of substance. It contains exactly 6.02214076 x 10^23 elementary entities, such as atoms or molecules.
What is the equivalent of 1 Watt in terms of other SI units?
- A 1 Joule per second
- B 1 Newton per meter
- C 1 Ampere per volt
- D 1 Joule-second
Correct answer: 1 Joule per second
The Watt is the SI unit of power, defined as the rate of energy transfer. One Watt is equal to one Joule of work performed per second.
Which SI prefix represents a factor of 10^-9?
- A Micro
- B Pico
- C Nano
- D Femto
Correct answer: Nano
The prefix 'nano-' denotes a factor of one billionth, or 10^-9. It is commonly used in fields like nanotechnology and electronics to describe very small scales.
The unit 'Hertz' (Hz) measures the frequency of periodic phenomena. What is its fundamental SI dimension?
- A m/s
- B s^-1
- C kg/s
- D m^-2
Correct answer: s^-1
Hertz is defined as the number of cycles per second. Therefore, its dimension is the reciprocal of time, expressed as s^-1.
Which of these is the SI unit for measuring electrical capacitance?
- A Ohm
- B Farad
- C Coulomb
- D Siemens
Correct answer: Farad
The Farad (F) is the SI unit of capacitance, representing the ability of a body to store an electrical charge. One Farad is defined as one Coulomb per Volt.
Which SI unit is used to measure magnetic flux density?
- A Weber
- B Tesla
- C Henry
- D Lux
Correct answer: Tesla
The Tesla (T) is the SI derived unit of magnetic flux density or magnetic induction. One Tesla is equal to one Weber per square meter.
The Joule (J) is the SI unit for energy. Which of the following is also measured in Joules?
- A Applied force
- B Mechanical power
- C Work done
- D Momentum
Correct answer: Work done
Work and energy are physically equivalent and share the same SI unit, the Joule. Work is defined as force applied over a distance (Newton-meters).
What is the standard SI unit for Plane Angle?
- A Degree
- B Steradian
- C Radian
- D Gradian
Correct answer: Radian
The Radian is the SI unit for measuring plane angles. While degrees are commonly used in everyday life, the Radian is the mathematically preferred unit in the SI system.
Which unit is used to measure the 'inductance' of an electrical conductor?
- A Henry
- B Weber
- C Tesla
- D Ohm
Correct answer: Henry
The Henry (H) is the SI derived unit of electrical inductance. It is named after the American scientist Joseph Henry, who discovered self-inductance.
The 'Becquerel' (Bq) is the SI unit for which physical quantity?
- A Absorbed radiation dose
- B Radioactive activity
- C Dose equivalent
- D Luminous flux
Correct answer: Radioactive activity
The Becquerel measures the activity of a quantity of radioactive material. One Becquerel is defined as the activity wherein one nucleus decays per second.
What does the SI prefix 'Tera' represent?
- A 10^9
- B 10^12
- C 10^15
- D 10^18
Correct answer: 10^12
The prefix 'tera-' indicates a factor of one trillion, or 10^12. It is frequently used in computing to describe data storage capacities, such as terabytes.
Which of the following is the SI unit for electric potential difference?
- A Ampere
- B Watt
- C Volt
- D Coulomb
Correct answer: Volt
The Volt (V) is the derived SI unit for electric potential, electromotive force, and potential difference. It is defined as the potential difference across a conductor when one ampere of current dissipates one watt of power.
The 'Gray' (Gy) is the SI unit for which of the following?
- A Absorbed radiation dose
- B Illuminance
- C Radiation dose equivalent
- D Electric conductance
Correct answer: Absorbed radiation dose
The Gray (Gy) is the SI unit of absorbed radiation dose, measuring the energy deposited by ionizing radiation per unit mass of matter. One Gray equals one joule of radiation energy absorbed per kilogram. The Sievert measures the related but distinct quantity of radiation dose equivalent, which accounts for biological effectiveness.
Which unit is defined as the 'Luminous flux' emitted by a source?
- A Lux
- B Candela
- C Lumen
- D Nit
Correct answer: Lumen
The Lumen (lm) is the SI derived unit of luminous flux, a measure of the total amount of visible light emitted by a source. It differs from the candela, which measures intensity in a specific direction.
What is the SI unit for the coefficient of dynamic viscosity?
- A Pascal-second
- B Newton-second
- C Centipoise
- D Centistoke
Correct answer: Pascal-second
The SI unit for dynamic viscosity is the Pascal-second (Pa·s). While the Poise is often used in older texts, the Pascal-second is the standard unit within the International System.
Which of these is the base SI unit for Mass?
- A Gram
- B Milligram
- C Kilogram
- D Tonne
Correct answer: Kilogram
The kilogram (kg) is the only SI base unit that includes a prefix. It was originally defined by a physical prototype but is now defined in terms of the Planck constant.
The 'Siemens' (S) is the SI unit for measuring which property?
- A Electric resistance
- B Electric conductance
- C Magnetic permeability
- D Capacitive reactance
Correct answer: Electric conductance
Siemens is the SI unit for electrical conductance, which is the reciprocal of electrical resistance. Therefore, one Siemens is equal to one divided by one Ohm (A/V).