Physics · Science General

Units and Measurement

998 Questions

Master the fundamentals of physics with these practice questions on units and measurement. The topics include fundamental SI units, derived quantities, and specific units for power, force, and light. These questions are essential for building a strong foundation for competitive exams.

SI fundamental unitsUnits of powerDerived quantities unitsThermal energy unitsVolume measurement unitsElectric current units

Units and Measurement Questions

Multiple choice standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

Units of Planck's constant in CGS system are:

  1. Erg per second

  2. Second per erg

  3. Erg second

  4. Erg per second per second
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Planck's constant, symbolized h, relates the energy in one quantum (photon) of electromagnetic radiation to the frequency of that radiation.  In the centimeter-gram-second (CGS) or small-unit metric system, it is equal to approximately $6.626176\times 10^{-27}\,$Erg Second.

Multiple choice standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

The ratio of SI unit to CGS unit of G is

  1. $10^{3}$
  2. $10^{2}$
  3. $10^{-2}$
  4. $10^{-3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
SI unit of G is  $\dfrac{N m^2}{kg^2}$.
CGS unit of G is  $\dfrac{dyne \ cm^2}{gm^2}$
We know that  $1 \ N = 10^5 \ dyne$ and $1 \ m = 10^2 \ cm$ and $1 \ kg = 10^3 \ gm$
So ratio of SI unit to CGS unit   $ = \dfrac{\dfrac{N  \ m^2}{kg^2}}{\dfrac{dyne \ cm^2}{gm^2}} = \dfrac{\dfrac{10^5 \ dyne \ (10^2 \ cm)^2}{(10^3 \ gm)^2}}{\dfrac{dyne \ cm^2}{gm^2}} = 10^3$
Correct answer is option A.
Multiple choice physics moving charges and magnetism field due to a current carrying conductor magnetic field due to a straight current carrying conductor magnetic field lines due to current

SI unit of permittivity of free space is:

  1. Farad

  2. Weber
  3. ${ C }^{ 2 }{ N }^{ -1 }{ m }^{ -2 }$
  4. ${ C }^{ 2 }{ N }^{ -1 }{ m }^{ -1 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Coulombic force between two charges is given by

F=1/4π€ (q'.q″/r²)

From here, the SI UNIT of permittivity comes out is

= coulomb²/Newton-meter²

C²/N-m²

Multiple choice physics heat engine: second law of thermodynamics second law of thermodynamics the second law of thermodynamics second law of thermodynamic

Consider a new system of units in which c (speed of light in vacuum), h(Planck's constant) and G (gravitational constant) are taken as fundamental units. Which of the following would correctly represent mass in this new system?

  1. $\sqrt{\dfrac{hc}{G}}$
  2. $\sqrt{\dfrac{Gc}{h}}$
  3. $\sqrt{\dfrac{hG}{c}}$
  4. $\sqrt{hGc}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Consideration anew system of units in which speed of light in vaccum$=e$Plank's constant$=h$

Gravitational constant$=G$
Mass in the new system
$F=\cfrac{1}{2}mv^2=h\gamma$
Now,
Using the method of dimension we say that,
Here
${e}=LT^{-1}$
$[G]=M^{-1}L^3T^{-2}$
$[h]=M^1L^2T^{-2}$
Let, $mac^xG^0h^z$
By substituting the dimension of each quantity in both the sides
$M=(LT^{-1})^x(M^{-1}L^3T^{-2})^y(ML^2T^{-1})^z\M=(M^{y+z}L^{x+3y+2z}T^{x-2y-x})$
By equating the power of $M,L\quad and T$ in both the sides
$-y+z=1\x+3y+2z=0\-x-2y-z=0$
By solving the above equations
We get,
$x=\cfrac{1}{z},y=-\cfrac{1}{z},z=\cfrac{1}{z}$
So, $[m]=e^{1/2}G^{-1/2}h^{1/2}\ \quad=\sqrt{\cfrac{hc}{G}}$

Multiple choice physics measurements and units summary of si units fundamental quantities system of units

In International System of units, there are seven base quantities whose units are defined. Which physical quantity has a prefix with its unit?

  1. Mass

  2. Thermodynamic temperature

  3. Luminous intensity

  4. Amount of substance
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Unit of mass is kilogram and here, kilo is a prefix used in the unit. Thus mass is the physical quantity which has prefix with its unit.