Tag: magnetic flux

Questions Related to magnetic flux

State whether the following two statements are true or false
(i) Li has the same units as that of magnetic flux.
(ii) Li has the units volt-second and magnetic flux has the units coulomb-ohm.

physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

  1. T T

  2. F F

  3. T F

  4. F T

Show answer
Correct Option: C
Explanation:

$\begin{array}{l} \left( 1 \right) This\, \, is\, \, True\, \, because\, \, \phi =Li \ \left( 2 \right) This\, \, is\, \, False\, \, because \ v=L\left( { \dfrac { { di } }{ { dt } }  } \right)  \ \Rightarrow L=\dfrac { v }{ q }  \ \Rightarrow Li=\dfrac { v }{ B }  \ Hence, \ option\, \, C\, \, is\, correct\, \, answer. \end{array}$

The ratio of magnetic inductions at the centre of a circular coil of radius a and on its axis at a distance equal to its radius, will be -

physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

  1. $\frac { 1 }{ \sqrt { 2 } } $

  2. $\frac { \sqrt { 2 } }{ 1 } $

  3. $\frac { 1 }{ 2\sqrt { 2 } } $

  4. $\frac { 2\sqrt { 2 } }{ 1 } $

Show answer
Correct Option: C

The sun delivers ${10^3}W/{m^2}$ of electromagnetic flux to the earth's surface. The solar energy incident on the roof in $1$houre will be 

physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

  1. $5.76 \times {10^8}J$

  2. $5.76 \times {10^7}J$

  3. $5.76 \times {10^6}J$

  4. $5.76 \times {10^5}J$

Show answer
Correct Option: C

Light with an energy flux of $18 w/cm^2$ falls on a non-reflecting surface at normal incidence. If the surface has an area of $20 cm^2$. Find the average force exerted on the surface during a 30 minute time

physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

  1. $1.2 \times 10 ^ { - 6 } N$

  2. $2 .4\times 10 ^ { - 6 } N$

  3. $2.16 \times 10 ^ { - 3 } \mathrm { N }$

  4. $1.5\times 10 ^ { - 6 } N$

Show answer
Correct Option: A
Explanation:

The total energy falling on the surface is $U = \left( {18W/c{m^2}} \right) \times \left( {20c{m^2}} \right) \times \left( {30 \times 60} \right) = 6.48 \times {10^5}J$

therefore$,$ the total momentum delivered is 
$P = \dfrac{U}{c} = \dfrac{{\left( {6.48 \times {{10}^5}J} \right)}}{{\left( {3 \times {{10}^8}\,m/s} \right)}} = 2.16 \times {10^{ - 3}}\,kgm/s$
The average force exerted on the surface is 
$F = \dfrac{p}{t} =  = \dfrac{{2.16 \times {{10}^{ - 3}}}}{{0.18 \times {{10}^4}}} = 1.2 \times {10^{ - 6}}N$
Hence,
option $(A)$ is correct answer.

The electric field in a certain region is $\left( 10\hat { i } +5\hat { j }  \right) \times { 10 }^{ 4 }N/C$. What is the flux due to this field over an area of $\left( 3\hat { i } +3\hat { j }  \right) \times { 10 }^{ -2 }{ m }^{ 2 }$ in ${ Nm }^{ 2 }/C?$

physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

  1. $4.5\times { 10 }^{ 3 }$

  2. $3.5\times { 10 }^{ 3 }$

  3. $2.5\times { 10 }^{ 3 }$

  4. $1.5\times { 10 }^{ 3 }$

Show answer
Correct Option: A

Current flowing through a long solenoid is varied. Then, magnetic flux density of the magnetic field inside varies ::

physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

  1. inversely with $I$

  2. inversely with ${ I }^{ 2 }$

  3. directly with $I$

  4. directly with ${ I }^{ 2 }$

Show answer
Correct Option: C

A wire of length $'\ell '$ is used to make a circular coil of 'n' no. of turns. A current 'I' passes through the coil. If twice the length of wire is used now to make the coil with turns of same radius, making same current flow through it, the magnetic field at the centre of coil will become.

physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

  1. 1.5 times than earlier

  2. 0.5 time than earlier

  3. 2 times than earlier

  4. 4 time than earlier

Show answer
Correct Option: B

The magnetic flux linked with a coil is given by the equation $ \phi = 5t^2 + 3t + 6 $. The induced e.m.f. in the coil in the fourth second will be 

physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

  1. 20 V

  2. 40 V

  3. 10 V

  4. 80 V

Show answer
Correct Option: C

A closely wound flat circular coil of 25 turns of wire has diameter of =f 10 cm and carries a current of 4 amperes. determine the magnetic flux density at the centre of the coil:-

physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

  1. $ 1.679 \times 10^{-5} T $

  2. $ 2.028 \times 10^{-4} T $

  3. $ 1.257 \times 10^{-3} T $

  4. $ 1.512 \times 10^{-6} T $

Show answer
Correct Option: C

The magnetic flux linked with a coil, in webers, is given by the equation $\phi =4t^{2}-3t+7$. Then the magnitude of induced emf at 2 sec will be....

physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

  1. 15 v

  2. 19 v

  3. 17 v

  4. 21 v

Show answer
Correct Option: C