Tag: summary of si units

Questions Related to summary of si units

SI unit of moment of couple is ____.

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

  1. $N m$

  2. $dyne \ cm$


  3. $N m^{-2}$

  4. none of the above

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Correct Option: A
Explanation:
Moment of couple is torque which is equal to the product of force applied to the distance.
Moment of couple   $\tau = rF$
SI unit of moment of couple is $Nm$

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

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

  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. $[M^0 L^2 T^0 A^1]$

Show answer
Correct Option: A
Explanation:

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

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

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

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

$= [M^o LAT^o]$

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

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

  1. $r^2ds \cos \theta$

  2. $\dfrac{ds \cos \theta }{r^2}$

  3. $\dfrac{ds\cos \theta }{r}$

  4. $\dfrac{r^2}{ds \cos \theta}$

Show answer
Correct Option: B
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.

Unit of density and relative density are same.

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

  1. True

  2. False

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Correct Option: B
Explanation:

Unit of density is $g/cm^3$ whereas relative density is unitless. Thus the given statement is false.

Hertz is the unit of

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

  1. wavelength

  2. amplitude

  3. frequency

  4. None of these

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Correct Option: C
Explanation:

Hertz is the fundamental unit of frequency.

The SI unit of electron mobility is  :

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

  1. ${M^2}{S^{ - 1}}V - 1$

  2. $=m^2 s^{-1}V^{-1}$

  3. $m{s^{ - 1}}V$

  4. ${m^2}{s^{ - 2}}V$

Show answer
Correct Option: B
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 $=\dfrac{m/s}{V/m}$
$=m^2/Vs$
$=m^2 s^{-1}V^{-1}$

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

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

  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. $\displaystyle { kg}^{2}{ m }^{ 2 }{ s }^{ 3}{ A }^{ -1 }$

Show answer
Correct Option: A
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  $kg \ m^2s^{3}A^{-1}$.

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

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

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

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

  3.  $ N$ and $ Pa$

  4. None of these

Show answer
Correct Option: A,C
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 $(Pa)$.

The S.I. unit of magnetic pole strength is_______

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

  1. $A.{ m }^{ 2 }$

  2. $A.{ m }^{ -1 }$

  3. A.m

  4. $A/{ m }^{ 2 }$

Show answer
Correct Option: C
Explanation:

Magnetic pole strength is the strength of a magnetic pole to attract magnetic materials towards itself . S.I. unit of magnetic pole strength is Ampere-meter $(A\,m)$.

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

physics dynamics - explaining motion system of unit summary of si units system of units

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

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

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

  4. $\displaystyle \frac { 1 }{ 100 } { m }/{ { s }^{ 2 } }$

Show answer
Correct Option: A
Explanation:

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

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