The force on a conductor of length l placed in a magnetic field o

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 Multiple Choice QuestionsMultiple Choice Questions

81.

The amplitude of the sinusoidially oscillating electric field of a plane wave is 60 V/m. Then the amplitude of magnetic field is

  • 2 × 102 T

  • 6 × 107 T

  • 6 × 102 T

  • 2 × 10-7 T


82.

An α-particle with a specific charge of 2.5 × 107 C kg-1 moves with a speed of 2 x 105 ms-1 in a perpendicular magnetic field of 0.05 T. Then the radius of the circular path described by it is

  • 8 cm

  • 4 cm

  • 16 cm

  • 2 cm


83.

A cyclotron can be used to accelerate

  • α-particles

  • β-particles

  • neutrons

  • neutrino


84.

A straight conductor of length l carrying a current I, is bent in the form of a semicircle. The magnetic field (in tesla) at the centre of the semicircle is

  • π2Il × 10-7

  • πIl × 10-7

  • πll2 × 10-7

  • πl2l × 10-7


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85.

Which of the following graphs represents variation of magnetic field B with distance r for  straight long wire carrying current ? 


86.

The force between two magnetic poles is F. If the distance between the poles and pole strengths of each pole are doubled, then the force experienced is

  • 2 F

  • F2

  • F4

  • F


87.

A magnet of length 0.1 m and pole strength 10-4 A-m is kept in a magnetic field of 30 Wb/m2 at an angle 30°. The couple acting on it is 

  • 7.5 × 10-4 Nm

  • 3.0 × 10-4 Nm

  • 1.5 × 10-4 Nm

  • 6.0 × 10-4 Nm


88.

A circular coil carrying a current has a radius R. The ratio of magnetic induction at the centre of the coil and at a distance equal to 3R from the centre of the coil on the axis is

  • 1 : 1

  • 1 : 2

  • 8 : 1

  • 1 : 8


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89.

The force on a conductor of length l placed in a magnetic field of magnitude B and carrying a current I is given by (θ is the angle, the conductor makes with the direction of B)

  • F = I l B sin θ

  • F = I2 l B2 sin θ

  • F = I l B cos θ

  • F = I2lB sin θ


A.

F = I l B sin θ

F = I l B sin θ


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90.

A needle made of bismuth is suspended freely in a magnetic field. The angle which the needle makes with the magnetic field is

  • 45°

  • 90°

  • 180°


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