An α-particle with a specific charge of 2.5 &time

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 Multiple Choice QuestionsMultiple Choice Questions

321.

An electric current passes through a long straight copper wire. At a distance 5 cm from the straight wire, the magnetic field is B. The magnetic field at 20 cm from the straight wire would be

  • B6

  • B4

  • B3

  • B2


322.

In a hydrogen atom, the electron is making 6.6 × 1015  rps in a circular path of radius 0.53 A. What is the magnetic induction produced at the centre of orbit ?

  • 6.3 T

  • 12.6 T

  • 18.9 T

  • 25.2 T


323.

A cell is connected between the points A and C of a circular conductor ABCD with O as centre and angle AOC = 60°. If B1 and B2 are the magnitudes of the magnetic fields at O due to the currents in ABC and ADC respectively, then ratio B1B2 is 

  • 1

  • 2

  • 5

  • 6


324.

An electron of mass m and charge q is travelling with a speed v along a circular path of radius r at right angles to a uniform of magnetic field B. If speed of the electron is doubled and the magnetic field is halved, then resulting path would have a radius of

  • r4

  • r2

  • 2r

  • 4r


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325.

A particle of charge -16 x 10-18 moving with velocity 10 ms-1 along the x-axis enters a region where a magnetic field of induction B is along the y-axis, and an electric field of magnitude 104 Vm-1 is along the negative z-axis. If the charged particle continues moving along the x-axis, then magnitude of B is

  • 10-3 Wbm-2

  • 103 Wbm-2

  • 105 Wbm-2

  • 1016 Wbm-2


326.

The ratio of voltage sensitivity (VS ) and current sensitivity (IS ) of a moving coil galvanometer is

  • 1G

  • 1G2

  • G

  • G2


327.

A galvanometer acting as a voltmeter should have

  • low resistance in series with its coil

  • low resistance in parallel with its coil

  • high resistance in series with its coil

  • high resistance in parallel with its coil


328.

In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will be a

  • helix

  • straight line

  • ellipse

  • circle


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329.

The coil in a tangent galvanometer is 16 cm in radius. If a current of 20 mA is to produce a deflection of 45°, then the number of turns wound on it, is (Take horizontal component of earth's magnetic field = 0.36 x 10-4 T  and µ0 = 4π x 10-7 WbA-1 m-1 )

  • 229

  • 458

  • 689

  • 916


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330.

An α-particle with a specific charge of 2.5 × 107 C-kg-1 moves with a speed of 2 × 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


C.

16 cm

      r = mvBqr  = vBqm = 2 × 1050.05 × 2.5 × 107        = 2 × 10712.5 × 107 = 20012.5 cm        = 16 cm


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