Tag: measurements and units

Questions Related to measurements and units

The dimensional formula for magnetic flux is:

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

  1. $(ML^2T^{-2}A^{-1})$

  2. $(ML^3T^{-2}A^{-2})$

  3. $(M^0L^{-2}T^{2}A^{-2})$

  4. $(ML^2T^{-1}A^{2})$

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Correct Option: A
Explanation:

The magnetic flux if given by

$\phi=BAcos\theta$
If $cos\theta=1$
The maximum magnetic flux, $\phi=BA$. . . . . .(1)
where, $B=$ magnetic field
$A=area$ 
The dimensional formula for magnetic field,
$F=qvB$
where, $v=$ velocity
$q=$ charge,
$B=$ magnetic field
$[B]=\dfrac{M^1 L^1T^{-2}}{[A^1 T^1][L^1T^{-1}]}$
$[B]=[M^1L^0T^{-2}A^{-1}]$
for area, $[A]=[M^0 L^2 T^0]$
The dimensional formula for magnetic flux,
$[\phi]=[M^1L^0 T^{-2}A^{-1}].[M^0L^2T^0]$
$[\phi]=[M^1L^2T^{-2}A^{-1}]$
The correct option is A.

The SI unit of gravitational potential is :

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

  1. Joule/kg

  2. Joule$^2$/kg

  3. kg/Joule

  4. Joule/kg$^2 $

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Correct Option: A
Explanation:

The gravitational potential at a point is the potential energy associated with a unit mass due to its position in the gravitational field of another body. Gravitational potential is the amount of work done in bringing a body of unit mass from infinity to that point.
Gravitational potential (V) $=\dfrac{Work done}{Mass}=\dfrac{W}{m}$
Gravitational potential  is a scalar quantity and the  SI unit is $J/kg$. 

Siemen is the SI unit of

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

  1. resistivity

  2. resistance

  3. conductivity

  4. conductance

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Correct Option: D
Explanation:

Conductance, $G=\dfrac {1}{resistance}=mho(\Omega^{-1})$ or Siemens (S)


Unit for conductivity is $\mu S/cm$

Which of the following unit is not a fundamental unit:

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

  1. Meter

  2. Litre

  3. Second

  4. Kilogram

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Correct Option: B
Explanation:

Litre is not a fundamental unit.

The SI unit of $ \dfrac{1}{2 \pi \sqrt{LC}}$ is equivalent to that of :

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

  1. time period

  2. frequency

  3. wavelength

  4. wave number

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Correct Option: B
Explanation:

The angular frequency of current oscillations in an LC circuit is given by $\omega =\dfrac{1}{\sqrt {LC}}$ and $\omega = 2\pi f$.
$\Rightarrow f= \dfrac{1}{2\pi \sqrt{LC}}$ and the unit is equivalent to that of frequency.

The SI unit of coefficient of mutual inductance of a coil is

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

  1. henry

  2. volt

  3. farad

  4. weber

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Correct Option: A
Explanation:

The henry (symbolized H) is the Standard International ( SI ) unit of coefficient of mutual inductance of a coil .

The S.I. unit of pole strength is

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

  1. $Am^2$

  2. $Am$

  3. $Am^{-1}$

  4. $Am^{-2}$

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Correct Option: B
Explanation:

Pole strength, $m=\displaystyle \frac {Magnetic \ moment}{2l}=\frac {Am^2}{m}=Am$

Rate of energy dissipation is measured in 

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

  1. Watt

  2. Joule

  3. Weber

  4. Joule / coulomb

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Correct Option: B

The units of fundamental physical quantities are known as ________ units.

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

  1. Derived

  2. Absolute

  3. Supreme

  4. Fundamental

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Correct Option: D
Explanation:

The units of fundamental physical quantities are known as fundamental units.

Which of the following does not has fundamental unit?

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

  1. Mass

  2. Time

  3. Force

  4. Electric current

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Correct Option: C
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.