Tag: physics

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

Which of the following does not has fundamental unit?

  1. Mass

  2. Time

  3. Force

  4. Electric current
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The fundamental units are defined arbitrarily and they are used to derive of others unit. Generally the most common fundamental units are mass, time, length and current.

As the unit of force can be derived from three fundamental units, mass, length and time so the force does not has fundamental unit.

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.