A galvanometer of resistance 20 Ω is to be converted i

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 Multiple Choice QuestionsMultiple Choice Questions

91.

Two long straight wires are set parallel to each other. Each carries a current in the same direction and the separation between them is 2 r. The intensity of the magnetic field mid-way between them is

                   

  • μ0ir

  • 4μ0ir

  • Zero

  • μ0i4r


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92.

A galvanometer of resistance 20 Ω is to be converted into an ammeter of range 1 A. If a current of 1 mA produces full scale deflection, the shunt required for the purpose is

  • 0.01 Ω

  • 0.05 Ω

  • 0.02 Ω

  • 0.04 Ω


C.

0.02 Ω

S = IgGI - Ig = 10-3 × 201 - 1 × 10-3 = 0.02 Ω


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93.

A magnetic needle is kept in a non-uniform magnetic field. It experiences

  • force and torque

  • a force but not a torque

  • a torque but not a force

  • neither a force nor a torque


94.

A wire in the form of a circular loop of one turn carrying a current produces a magnetic field B at the centre. If the same wire is looped into a coil of two turns and carries the same current, the new value of magnetic induction at the centre is

  • 3B

  • 5B

  • 4B

  • 2B


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95.

To send 10% of the main current through a moving coil galvanometer of resistance 99 ohm, the shunt required is

  • 10 ohm

  • 9.9 ohm

  • 9 ohm

  • 11 ohm


96.

A charged particles moves along the line AB which lies in the same plane of a circular loop of conducting wire as shown in the figure. Then

            

  • no current will be induced in the loop

  • the current induced in the loop will change its direction as the charged particle passes by

  • the current induced will be anti-clockwise

  • the current induced will be clockwise


97.

A magnet N-S is suspended from a spring and when it oscillates, the magnet moves in and out of the coil C. The coil is connected to a galvanometer G. Then, as the magnet oscillates

              

  • G shows no deflection

  • G shows deflection to the left and right but the amplitude steadily decreases.

  • G shows deflection to the left and right with constant amplitude.

  • G shows deflection on one side.


98.

The maximum current that can be measured by a galvanometer of resistance 40 Ω, is 10 mA. It is converted into a voltmeter that can read upto 50 V. The resistance to be connected in series with the galvanometer (in ohms) is

  • 2010

  • 4050

  • 5040

  • 4960


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99.

A rectangular coil of 300 turns has an average area of 25 cm x 10 cm . The coil rotates with a speed of 50 cps in uniform magnetic field of strength 4 × 10-2 T about an axis perpendicular to the field. The peak value of the induced emf is (in volt)

  • 300 π

  • 3000 π

  • 3 π

  • 30 π


100.

A vertical circular coil ofradius 0.1 m and having 10 turns carries a steady current. When the plane of the coil is normal to the magnetic meridian, a neutral point is observed at the centre of the coil. If BH = 0314 × 10-4 T, the current in the coil is

  • 0.5 A

  • 0.25 A

  • 2 A

  • 1 A


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