Tag: magnetic flux density

Questions Related to magnetic flux density

A square loop of side 12 cm and resistance 0.60$\Omega$ is placed vertically in the east-west plane. A uniform magnetic field of 0.1 T is setup across the plane in north-east direction. The magnetic field is decreased to zero in 0.6 s at a steady rate. The magnitude of current during this time interval is

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

  1. $1.42 \times 10^{-3} A$

  2. $2.67 \times 10^{-3} A$

  3. $3.41\times 10^{-3} A$

  4. $4.21 \times 10^{-3} A$

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Correct Option: B
Explanation:

Here, Area $A=l^2=(12cm)^2=1.4\times 10^{-2} m^2$
$R=0.60\omega, B _1=0.10 T,\theta=45^0$
$B _2=0,dt=0.6$ s
Initial flux,
$\phi _1=B _1Acos\theta$
      $=0.10\times1.4\times10^{-2}\times cos 45^0$
      $=9.8\times 10^{-4}$

final flux, $\phi _2$=0
Induced emf,$E=\dfrac{| d\phi |}{dt}=\dfrac{|\phi _2-\phi _1|}{dt}$
                      $E=\dfrac{|9.8\times 10^{-4}|}{0.6}s\\,\,\,\,\,=1.6\times10^{-3}V$
Current, $I=\dfrac{E}{R}=\dfrac{1.6\times\times 10^{-3}}{0.6}=2.67 \times 10^{-3}$

When the normal to a coil points in the direction of magnetic field (B), then flux is 

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

  1. a scalar quantity

  2. a vector quantity

  3. neither scalar nor vector

  4. uncertain

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Correct Option: A
Explanation:

Dot product of field and area vectors is flux . $\Phi=B.dS$, and we know dot product of two vectors is a scalar quantity.
Therefore, flux is scalar.

Current $i _0$ is being carried by an infinite wire passing through origin along the direction $\hat{i} + \hat{j} + \hat{k}$. Find magnetic field due to the wire at point $(1 m, 0, 0)$.

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

  1. $\dfrac{(\mu _0 i)}{(2 \pi)} T$

  2. $\dfrac{(\mu _0 i)}{(\sqrt{2} \pi)} T$

  3. $\dfrac{(\mu _0 i)}{(4 \pi)} T$

  4. $\dfrac{(\sqrt{3} \mu _0 i)}{(2 \sqrt{2} \pi)} T$

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Correct Option: D

A charge q is placed at the centre of a cylinder of radius R and length 2R. Then electric flux through the curved surface of the cylinder is 

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

  1. $\cfrac { q }{ 2 { \epsilon } _{ 0 } } $

  2. $\cfrac { q }{ 4 { \epsilon } _{ 0 } } $

  3. $\cfrac { q }{ \sqrt { 2 } { \epsilon } _{ 0 } } $

  4. $\cfrac { q }{ 2\sqrt { 2 } { \epsilon } _{ 0 } } $

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Correct Option: C

A Point source generates 10 J of light energy in 2 s. The luminous flux of source is: 

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

  1. 5 lumen

  2. 10 lumen

  3. 50 lumen

  4. none of these

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Correct Option: A
Explanation:

The luminous flux of source is the rate at which light energy flows from the source:

luminous flux =10 J/ 2 s= 5 lumen.
so the correct option is A.

A cyclotron in which protons are accelerated has a flux density 1.57T. The variation of frequency of electric field is (in Hz) 

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

  1. $4.8 \times 10 ^ { 8 }$

  2. $8.4 \times 10 ^ { 8 }$

  3. $2.5 \times 10 ^ { 7 }$

  4. $4.8 \times 10 ^ { 6 }$

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Correct Option: C

The electric field potential in space has the form $V(x,y,z)=-2xy+3yz^{-1}$. The electric field intensity $\vec E$ magnitude at the point (-1,1,2) is

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

  1. $2 \sqrt{86} units$

  2. $2\sqrt{163} units$

  3. $\sqrt{163} units$

  4. $ \sqrt{86} units$

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Correct Option: A

An iron rod of volume ${ 10 }^{ -4 }{ m }^{ 3 }$ and relative permeability 1000 is placed inside a long solenoid would with. 5 turn ism. If a current of 0.5 A is passed through the solenoid, then the magnetic moment of the rod is:

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

  1. 10 ${ Am }^{ 2 }$

  2. 15 ${ Am }^{ 2 }$

  3. 20 ${ Am }^{ 2 }$

  4. 25 ${ Am }^{ 2 }$

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Correct Option: D

Unit of magnetic flux density is 

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

  1. $weber/metre$

  2. $weber$

  3. $weber/m^{2}$

  4. $ampere/m$

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Correct Option: C

Current in a circular coil having negligible resistance and inductance 0.1 H is increasing at the rate of $1 As^{-1}$. The power generated in the coil when the magnetic flux linked with it is 0.1 Wb will be:-

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

  1. 0.05 W

  2. 0.1W

  3. 1 W

  4. 10 W

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Correct Option: B