A wire carrying currenti is shaped as shown. Section AB is a quar

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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


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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


A.

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

By Grip rule magnetc field due to straight segment of current at C = zero. Magnetic field due to quarter circle at

               C = μ0I8r

vertically down to the paper.


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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
523 Views

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
740 Views

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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

1929 Views

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