Tag: physics

Questions Related to physics

MKS system means

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. Millimeter, kilometre, seconds

  2. Metre, kilogram, seconds

  3. Millisecond, kilolitre, seconds

  4. Milligram, kilogram, seconds

Show answer
Correct Option: B
Explanation:

In MKS system,M stands for metre (length),K stands for kilogram(mass) and S stands for seconds(time).

Units of Planck's constant in CGS system are:

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. Erg per second

  2. Second per erg

  3. Erg second

  4. Erg per second per second

Show answer
Correct Option: C
Explanation:

Planck's constant, symbolized h, relates the energy in one quantum (photon) of electromagnetic radiation to the frequency of that radiation.  In the centimeter-gram-second (CGS) or small-unit metric system, it is equal to approximately $6.626176\times 10^{-27}\,$Erg Second.

If force (F), work (W) and velocity (V) are taken as fundamental quantities then the dimensional formula of time (T) is

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. $\left[ { W }^{ 1 }{ F }^{ 1 }{ V }^{ 1 } \right] $

  2. $\left[ { W }^{ 1 }{ F }^{ 1 }{ V }^{ -1 } \right] $

  3. $\left[ { W }^{ -1 }{ F }^{ -1 }{ V }^{ -1 } \right] $

  4. $\left[ { W }^{ 1 }{ F }^{ -1 }{ V }^{ -1 } \right] $

Show answer
Correct Option: D
Explanation:
We know,

$[W]=ML^2T^{-2}$

$[F]=MLT^{-2}$

$[V]=LT^{-1}$

Let,
$W^aF^bV^c=M^0L^0T$

$a+b=0$

$2a+b+c=0$, $a+c=0$

$-2a-2b-c=1$

$c=-1,a=1,b=-1$

Hence , $[T]=[WF^{-1}V^{-1}]$

Option $\textbf D$ is the correct answer

The ratio of SI unit to CGS unit of G is

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. $10^{3}$

  2. $10^{2}$

  3. $10^{-2}$

  4. $10^{-3}$

Show answer
Correct Option: A
Explanation:
SI unit of G is  $\dfrac{N m^2}{kg^2}$.
CGS unit of G is  $\dfrac{dyne \ cm^2}{gm^2}$
We know that  $1 \ N = 10^5 \ dyne$ and $1 \ m = 10^2 \ cm$ and $1 \ kg = 10^3 \ gm$
So ratio of SI unit to CGS unit   $ = \dfrac{\dfrac{N  \ m^2}{kg^2}}{\dfrac{dyne \ cm^2}{gm^2}} = \dfrac{\dfrac{10^5 \ dyne \ (10^2 \ cm)^2}{(10^3 \ gm)^2}}{\dfrac{dyne \ cm^2}{gm^2}} = 10^3$
Correct answer is option A.

Which of the following represents the magnitude of a temperature correctly?

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. 10 k

  2. 10 Kelvins

  3. 10 Ks

  4. 10 K

Show answer
Correct Option: D
Explanation:
Temperature is measured in Kelvin which is represented by $K$
Thus, $10 \ K$ is the correct representation of temperature.

1 Newton $=$

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. $10^4 dyne$

  2. $10^5 dyne$

  3. $10^6dyne$

  4. $10^7 dyne$

Show answer
Correct Option: B
Explanation:
S.I. unit of force is Newton and CGS unit of force is done.

We know $F=ma$
so, force can be expresses in S.I. Units as $Kg m s^{-2}$
and dyne can be expressed as $gcms^{-2}$
1 Newton= $kg ms^{-2}$ 
                 =$10^3 g*10^2 cms  s^{-2}$
                 =$10^5 g cm s^{-2}$
                 =$10^5 dyne$

A magnetic pole of pole strength 9.2 A m. is placed in a field of induction 50x10$^{-6}$ Tesla. The force experienced by the pole is :

electrostatic and magnetic analogy magnetism and matter magnetic effects of current and magnetism physics

  1. 46N

  2. 46$\times$10$^{-4}$N

  3. 4.6$\times$10$^{-4}$N

  4. 460N

Show answer
Correct Option: C
Explanation:

$m=9.2Am$
$B=50\times 10^{-6}T$
$F=B\times m$
$F=9.2\times 50\times 10^{-6}$
    $=4.6\times 10^{-4}N$

Two equal poles repel each other with a force of 10$^{-3}$ N. When placed 2cm apart in air, the pole strength of each is (in amp-m).

electrostatic and magnetic analogy magnetism and matter magnetic effects of current and magnetism physics

  1. 4$\pi $

  2. 2

  3. 4

  4. 2$\pi $

Show answer
Correct Option: B
Explanation:

$F=10^{-3}N$
$d=2cm$
$m _{1}=m _{2}=m$
$F=\dfrac{\mu _{0}m _{1}m _{2}}{4\pi d^{2}}$

$10^{-3} = \dfrac{10^{-7}\times m^{2}}{(2\times 10^{-2})^2}$
$m=2Am$

Force between two identical bar magnets whose centres are  $r meters $ apart is $4.8 N,$ when their axis are in the same line. If the separation is increased to $2r$ meters, the force between them is reduced to:

electrostatic and magnetic analogy magnetism and matter magnetic effects of current and magnetism physics

  1. 2.4 N

  2. 1.2 N

  3. 0.6 N

  4. 0.3 N

Show answer
Correct Option: B
Explanation:

$F=\dfrac{\mu _{0}m _{1}m _{2}}{4\pi d^{2}}$
$F\propto \dfrac{1}{d^{2}}$
$Fd^{2}=Constant$
$F _{1}d _{1}^{2}=F _{2}d _{2}^{2}$
$4.8\times r^2=F _{2}(2r)^2$
$F _{2}=1.2  N$

The magnetic induction at a distance d from the magnetic pole of the unknown strength m is B. If an identical pole is now placed at a distance of 2d from the first pole, the force between the two poles is          

electrostatic and magnetic analogy magnetism and matter magnetic effects of current and magnetism physics

  1. mB

  2. $\frac{mB}{2}$

  3. $\frac{mB}{4}$

  4. 2mB

Show answer
Correct Option: C
Explanation:
$B=\dfrac{\mu _{0}m}{4\pi d^{2}}$
$r=2d$
$F=\dfrac{\mu _{0}m _{1}m _{2}}{4\pi r^{2}}$
$F=\dfrac{\mu _{0}\times m\times m}{4\pi (d)^{2}}$
$F=\dfrac{\mu _{0}m^{2}}{4\pi \times 4d^{2}}$
$F=\dfrac{mB}{4}N$