Two similar coils of radius R are lying concentrically with thei

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 Multiple Choice QuestionsMultiple Choice Questions

161.

The magnetic field at the centre of a current carrying loop of radius 0.1 m is 55 times that at a point along its axis. The distance of this point from the centre of the loop is

  • 0.1 m

  • 0.2 m

  • 0.05 m

  • 0.25 m


162.

A wire carrying currenti is shaped as shown. Section AB is a quarter circle of radius r. The magnetic field is directed

               

  • perpendicular to the plane of the paper and directed into the paper

  • at an angle π4to the plane of the paper

  • along the bisector of the angle ACB away from AB

  • along the bisector of ACB towards AB


163.

The wire loop formed by joining two semicircular sections of radii R1 and R2 and centre C, carries a current I as shown. The magnetic field at C has a magnitude

                 

  • μ0I2 1R1 - 1R2

  • μ0I4 1R1 - 1R2

  • μ0I2 1R1 + 1R2

  • μ0I4 1R1 + 1R2


164.

A particle of unit mass and specific charge s is thrown from the wall perpendicularly to a wall at a distance d from the wall with speed 'v'. The minimum magnetic field produced so that the particle does not touch the wall, is:

  • vsd

  • 2vsd

  • v2sd

  • v4sd


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165.

A long straight wire of radius a carries a steady current I. The current is uniformly distributed over its cross-section. The ratio of the magnetic fields B and B' at radial distances straight a over 2 and 2a respectively, from the axis of the wire is,

  • 1 half
  • 1

  • 4

  • 4

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166.

A magnetic needle suspended parallel to a magnetic field requires square root of 3 J of work to turn it through  60o. The torque needed to maintain the needle in this position will be

  • 2 square root of 3 space straight J
  • 3 J

  • square root of 3 space J
  • square root of 3 space J
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167.

The ratio of amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagating in vacuum is equal to

  • the speed of light in vacuum

  • the reciprocal of the speed of light in vacuum

  • the ratio of magnetic permeability to the electric susceptibility of vacuum

  • the ratio of magnetic permeability to the electric susceptibility of vacuum

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168.

Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2I, respectively. The resultant magnetic field induction at the centre will be

  • fraction numerator square root of 5 straight mu subscript straight o straight I over denominator 2 straight R end fraction
  • fraction numerator 3 straight mu subscript straight o straight I over denominator 2 straight R end fraction
  • fraction numerator straight mu subscript straight o straight I over denominator 2 straight R end fraction
  • fraction numerator straight mu subscript straight o straight I over denominator 2 straight R end fraction


A.

fraction numerator square root of 5 straight mu subscript straight o straight I over denominator 2 straight R end fraction

The magnetic field (B) at the centre of circular current carrying coil of radius R and current I,

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169.

An electric dipole of moment p is placed in an electric field of intensity E. The dipole acquires a position such that the axis of the dipole makes an angle θ with the direction of the field. Assuming that the potential energy of the dipole to be zero when θ =90o, the torque and the potential energy of the dipole will respectively be

  • pE sin θ, pE cos θ

  • pE sin θ,-2pE cos θ

  • pE sin θ, 2 pE cos θ

  • pE sin θ, 2 pE cos θ

684 Views

170.

A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced emf is

  • one per revolution

  • twice per revolution

  • four times per revolution

  • four times per revolution

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