Tag: measurements and units

Quizzes (10) Questions (257)

Questions Related to measurements and units

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

The dimensions of ratio of magnetic flux $(\phi)$ and permeability $(u)$ are:

  1. $[M^0 L^1 A^1 T^0]$
  2. $[M^0 L^{-3} T^0 A^1]$
  3. $[M^0 L^{-1} T^1 A^{-1}]$
  4. $[M^0 L^2 T^0 A^1]$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Magnetic flux $= B.A.$
Permatibility $= \dfrac{B}{H} = \dfrac{J}{A.M}$

$= \dfrac{BA}{B/H}$

$= \dfrac{BAH}{B} = AH$

$= [L^2] [AC^{-1}]$

$= [M^o LAT^o]$

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

The solid angle subtended at any point inside the surface due to small area ds is given by 

  1. $r^2ds \cos \theta$
  2. $\dfrac{ds \cos \theta }{r^2}$
  3. $\dfrac{ds\cos \theta }{r}$
  4. $\dfrac{r^2}{ds \cos \theta}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The solid angle $\Omega=\dfrac{A}{r^2}$

where, $A=$ area
When solid angle subtended at any point inside the surface due to small area $ds$
$A=ds$ $cos\theta$
Solid angle $\Omega=\dfrac{dscos\theta}{r^2}$
The correct option is B.

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

The SI unit of electron mobility is  :

  1. ${M^2}{S^{ - 1}}V - 1$
  2. $=m^2 s^{-1}V^{-1}$
  3. $m{s^{ - 1}}V$
  4. ${m^2}{s^{ - 2}}V$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Electron mobility:- It is the ratio of velocity to electric field.

$\mu=\dfrac{v _e}{E}$. . . . . . .(1)
SI unit of velocity, $v _e$ $=m/s$
SI unit of electric field, $E$ $=V/m$
From equation (1),
SI unit of electron mobility is $=\dfrac{m/s}{V/m}$
$=m^2/Vs$
$=m^2 s^{-1}V^{-1}$

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

The dimensional formula of a physical quantity is $\displaystyle { M }^{ 1 }{ L }^{ 2 }{ T }^{ 3 }{ I }^{ -1 }$ .What is its SI unit?

  1. $\displaystyle { kg\quad m }^{ 2 }{ s }^{ 3 }{ A }^{ -1 }$
  2. $\displaystyle { kg\quad m }^{ 2 }{ s }^{ 2 }{ A }$
  3. $\displaystyle { kg\quad ms }^{ -3 }{ A }^{ 2 }$
  4. $\displaystyle { kg}^{2}{ m }^{ 2 }{ s }^{ 3}{ A }^{ -1 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

SI unit of $M$ is $kg$, that of $L$ is $m$, $T$ is $s$ and $I$ is $A$.
So, SI unit of $[M^1L^2T^{3}I^{-1}]$ is  $kg \ m^2s^{3}A^{-1}$.