Tag: summary of si units

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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. <span>$=m^2 s^{-1}V^{-1}$</span>

  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  $kg \ m^2s^{3}A^{-1}$.

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

Find the unit of the following derived quantities: 
(a) Force [Hint: Force = Mass $\times$ acceleration]
(b) Pressure $\left[Hint: Pressure =\frac{force}{Area}\right]$

  1. <span>$kg\,m\,s^{-2}$ and&nbsp;</span>$kg\,m^{-1}\,s^{-2}$

  2. $kg\,m\,s^{-1}$ and $Kg\,m^{-2}\,s^{-1}$

  3. <span>&nbsp;</span>$ N$&nbsp;and&nbsp;$ Pa$

  4. None of these
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation
Force   $F = ma$
So, unit of force is  $kg \ m/s^2$
Newton $(N)$ is also the unit of force.
Pressure   $P = \dfrac{F}{A}$
Unit of pressure   $ = \dfrac{kg \ m/s^2}{m^2} = kg \ m^{-1}s^{-2}$
Also, pressure is measured in Pascal $(Pa)$.
Multiple choice physics dynamics - explaining motion system of unit summary of si units system of units

If 1 kg wt = 10 N, the value of gravitational intensity will be 

  1. $\displaystyle 10{ m }/{ { s }^{ 2 } }$

  2. $\displaystyle \frac { 1 }{ 10 } { m }/{ { s }^{ 2 } }$

  3. $\displaystyle 1{ m }/{ { s }^{ 2 } }$

  4. $\displaystyle \frac { 1 }{ 100 } { m }/{ { s }^{ 2 } }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If $1\,kg\,wt=10\,N=F$

Then gravitational intensity is given by,
$g=\dfrac Fm$
$=\dfrac{10 }{1}=10 m/s^2$