A rectangular coil of area A, having number of turns N is rotated

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 Multiple Choice QuestionsMultiple Choice Questions

311.

A narrow beam of protons and deuterons, each having the same momentum, enters a  region of uniform magnetic field directed perpendicular to their direction of momentum. The ratio of the radii of the circular paths described by them is

  • 2 : 5

  • 3 : 2

  • 2 : 3

  • 1 : 1


312.

A horizontal overhead power line carries a current of 90 A in east to west direction. The magnitude and direction of the magnetic field due to the current 1.5 m below the line is

  • 2.5 x 10-5 T towards north

  • 3 x 10-5 T towards east

  • 1.2 x 10-5 T towards south

  • 1 x 10-5 T towards west


313.

A galvanometer has a resistance of 30 Q. It gives full scale deflection with a current of 2mA. Calculate, the value of the resistance needed to convert it into an ammeter of range 0 − 0.3 A. The value of the resistance needed to convert galvanometer into ammeter

  • 0.2 Ω

  • 0.3 Ω

  • 0.4 Ω

  • 0.52 Ω


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314.

A rectangular coil of area A, having number of turns N is rotated at f revolutions per second in a uniform magnetic field B. The maximum emf induced in the coil is

  • 2 πfNB

  • 2fNBA

  • 2 πfBA

  • 2 πfNBA


D.

2 πfNBA

The maximum emf induced in the coil is given by

    e = NBA (2πf) sin 90° = NBA (2πf) × 1

       = NBA (2πf) 


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315.

An electron having mass 9.1 x 10-31 kg moves in a circular path of radius 0.4 m with velocity 105 m/s in a magnetic field. The strength of magnetic field is

  • 1.56 × 10-5 T

  • 1.62 × 10-4 T

  • 1.42 x 10-6 T

  • 1.88 × 10-5 T


316.

A current of 0.4 A is passed through the coil of galvanometer having 500 turns and each turn has an average area of 3 x 10-4 m2 . If a torque of 2 Nm is required for this coil carrying some current to set it parallel to a magnetic field then the strength of magnetic field will be

  • 31 T

  • 33.34 T

  • 32 T

  • 40 T


317.

A galvanometer has a resistance of 4 Ω and a full scale deflection is produced by 12 mA current. What resistance must be connected in series with it to enable it to read 1.2 V ?

  • 45 Ω

  • 96 Ω

  • 80 Ω

  • 40 Ω


318.

An iron rod of volume 10-4 m3 and relative permeability 1000 is placed inside a long solenoid having 5 turns/cm. If a current of 5.0 A is passed through the solenoid, then magnetic moment of the rod is

  • 20 A-m2

  • 25 A-m2

  • 30 A-m2

  • 35 A-m2


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319.

In a uniform magnetic field, an π-shaped metal frame is located perpendicular to the plane of the conductor and varying with time at the rate (dB /dt)=0.20 T/s. A conducting connector starts moving with an acceleration a = 30 cm/s along the parallel bars of the frame. The length, l of the conductor is equal to 44 cm. If at the moment t = 0, the loop area and magnetic induction are equal to zero, then the emf induced in the loop t = 1s after the beginning of motion is

  • 6 × 10-4 V

  • 8 × 10-2 V

  • 6 × 10-2 V

  • 12 × 10-3 V


320.

A toroid having 200 turns carries a current of 1A. The average radius of the toroid is 10 cm. The magnetic field at any point in the open space inside the toroid is

  • 4 × 10-3 T

  • 0.5 × 10-3 T

  • 0

  • 3 × 10-3 T


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