JEE Physics - Magnetic effects of current and magnetism

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Question - 1

An electron is injected into a region of uniform magnetic field of induction with its velocity inclined to the field. The path of the electron is a

  • A circle
  • B parabola
  • C linear
  • D helix

Question - 2

The sensitiveness of a moving coil galvonometer can be increased by

  • A decreasing the area of the coil
  • B decreasing the number of turns in the coil
  • C increasing the area of the coil
  • D increasing the strength of the current

Question - 3

When a charged particle moves in a crossed electro-magnetic field with a velocity \(\vartheta \) without deviation, then

  • A \(\vartheta \) is constant and it is proportional to field
  • B \(\vartheta \) is constant and it is inversely proportional to field
  • C \(\vartheta \) is equal to ratio of electric field to magnetic field
  • D \(\vartheta \) is equal to ratio of magnetic field to electric field

Question - 4

A circular coil carrying current has magnetic induction B at its centre C. The radius of the coil is 3 cm. The distance of a point P from C, where the induction reduces to \(\frac { B }{ 8 } \) would be

  • A \(\sqrt { 3 } \)
  • B 2\(\sqrt { 3 } \)
  • C 3\(\sqrt { 3 } \)
  • D 9

Question - 5

Two infinite long wires at a distance of 1 m carry current of 1 mA in the same direction. Which one of the following is CORRECT?

  • A The given two wires repel each other
  • B Both wires experiences a force exactly equal to 2 X 10-7 Nm-1
  • C One of the two wires is replaced by an electron beam, then beam will not get deflected
  • D NONE OF THESE

Question - 6

A galvanometer can be used to measure voltage drop when it is connected with

  • A high resistance in series with it
  • B a high resistance in parallel with it
  • C a low resistance in series with it
  • D a low resistance in parallel with it

Question - 7

A ballistic galvanometer

  • A measure charge and it has small moment of inertia
  • B measures current and it has small moment of inertia
  • C measures charge and it has large moment of inertia
  • D measures current and it has large moment of inertia

Question - 8

A particle of charge q at a velocity \(\vartheta \)  moves in a circular path of radius r in a region of uniform magnetic field B. The work done by the magnetic field on the particle is

  • A zero
  • B equal to charge in kinetic energy
  • C \(2\pi q\vartheta Br\)
  • D \( q\vartheta Br\)

Question - 9

For a good voltmeter (moving coil type),

  • A both internal resistance and moment of inertia are large
  • B both internal resistance and moment of inertia is small
  • C internal resistance is large but moment of inertia is small
  • D internal resistance is small but moment of inertia is large

Question - 10

The electron of Bohr orbit of hydrogen atom revolves in its innermost orbit round the proton. The magnetic induction at the proton is of the order of

  • A 1 T
  • B 10 T
  • C 100 T
  • D 1000 T
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