JEE Questions for Physics Magnetism And Matter Quiz 7 - MCQExams.com

The magnetic induction in air at a distance d from an isolated point pole of strength m unit will be

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  • 2)
    Physics-Magnetism and Matter-78068.png
  • md
  • md2
A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through 60°. The torque required to maintain the needle in this position will be

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  • 2)
    Physics-Magnetism and Matter-78071.png

  • Physics-Magnetism and Matter-78072.png

  • Physics-Magnetism and Matter-78073.png
A long magnetic neddle of length 2L, magnetic moment M and pole strength m units is broken into two pieces at the middle. The magnetic moment and pole strength of each piece will be

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  • 2)
    Physics-Magnetism and Matter-78076.png

  • Physics-Magnetism and Matter-78077.png

  • Physics-Magnetism and Matter-78078.png
Two identical thin bar magnets each of length l and pole strength m are placed at right angle to each other with north pole of one touching south pole of the other. Magnetic moment of the system is
  • ml
  • 2ml
  • √2 ml
  • 1/2 ml
A small bar magnet has a magnetic moment 1.2 A-m2. The magnetic field at a distance 0.1 m on its axis will be: (µ0 = 4 π × 10–4 T-m/A)
  • 1.2 × 10–4 T
  • 2.4 × 10–4 T
  • 2.4 × 104 T
  • 1.2 × 104 T
What happens to the force between magnetic poles when their pole strength and the distance between them are both doubled
  • Force increases to two times to previous value
  • No change
  • Force decreases to half the previous value
  • Force increase to four times the previous value
The magnetic potential at a point on the axial line of a bar magnet of dipole moment M is V. What is the magnetic potential due to a bar magnet of dipole moment M/4 at the same point
  • 4 V
  • 2 V

  • Physics-Magnetism and Matter-78083.png

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A small bar magnet of moment M is placed in a uniform field H . If magnet makes an angle of 30° with field, the torque acting on the magnet is
  • MH
  • 2)
    Physics-Magnetism and Matter-78086.png

  • Physics-Magnetism and Matter-78087.png

  • Physics-Magnetism and Matter-78088.png
Two small magnets each of magnetic moment 10 A-m2 are placed in end-on position 0.1 m apart from their centres. The force acting between them is
  • 0.6 × 107 N
  • 0.06 × 107N
  • 0.6 N
  • 0.06 N
Magnetic lines of force
  • Always intersect
  • Are always closed
  • Tend to crowd far away from the poles of magnet
  • Do not pass through vacuum
Rate of change of torque τ with deflection θ is maximum for a magnet suspended freely in a uniform magnetic field of induction B, when
  • θ = 0oN
  • θ = 45oN
  • θ = 60oN
  • θ = 90oN
A magnet of magnetic moment M is rotated through 360° in a magnetic field H. The work done will be
  • MH
  • 2MH
  • 2πMH
  • Zero
The work done in turning a magnet of magnetic moment ‘M’ by an angle of 90° from the meridian is \'n\' times the corresponding work done to turn in through an angle of 60°, where \'n\' is given by
  • 1/2
  • 2
  • 1/4
  • 1
Force between two identical bar magnets whose centres are r metre apart is 4.8 N, when their axes are in the same line. If separation is increased to 2r, the force between them is reduced to
  • 2.4 N
  • 1.2 N
  • 0.6 N
  • 0.3 N
A bar magnet of magnetic moment 104J/T is free to rotate in a horizontal plane. The work done in rotating the magnet slowly from a direction parallel to a horizontal magnetic field of 4 × 10–5 T to a direction 60° from the field will be
  • 0.2 J
  • 2.0 J
  • 4.18 J
  • 2 × 102J
Magnetic lines of force due to a bar magnet do not intersect because
  • A point always has a single net magnetic field
  • The lines have similar charges and so repel each other
  • The lines always diverge from a single point
  • The lines need magnetic lenses to be made to intersect
A permanent magnet
  • Attracts all substances
  • Attracts only magnetic substances
  • Attracts magnetic substances and repels all non-magnetic substances
  • Attracts non-magnetic substances and repels magnetic substances
Two equal bar magnets are kept as shown in the figure. The direction of resultant magnetic field, indicated by arrow head at the point P is (approximately)
Physics-Magnetism and Matter-78096.png

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  • 2)
    Physics-Magnetism and Matter-78098.png

  • Physics-Magnetism and Matter-78099.png

  • Physics-Magnetism and Matter-78100.png
A short bar magnet placed with its axis at 30o with a uniform external magnetic field of 0.16 tesla experiences a torque of magnitude 0.032 joule. The magnetic moment of the bar magnet will be
  • 0.23 joule/tesla
  • 0.40 joule/tesla
  • 0.80 joule/tesla
  • Zero
The magnetic field due to a small magnetic dipole of magnetic moment M, at distance r from the centre on the equatorial line is given by (in M.K.S. system)

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  • 2)
    Physics-Magnetism and Matter-78104.png

  • Physics-Magnetism and Matter-78105.png

  • Physics-Magnetism and Matter-78106.png
A straight wire carrying current i is turned into a circular loop. If the magnitude of magnetic moment associated with it in M.K.S. unit is M, the length of wire will be

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  • 2)
    Physics-Magnetism and Matter-78109.png

  • Physics-Magnetism and Matter-78110.png

  • Physics-Magnetism and Matter-78111.png
For protecting a sensitive equipment from the external magnetic field, it should be
  • Placed inside an aluminum case
  • Placed inside an iron case
  • Wrapped with insulation around it when passing current through it
  • Surrounded with fine copper sheet
If a piece of metal was thought to be magnet, which one of the following observations would offer conclusive evidence
  • It attracts a known magnet
  • It repels a known magnet
  • Neither (a) nor (b)
  • It attracts a steel screw driver
The magnet can be completely demagnetized by
  • Breaking the magnet into small pieces
  • Heating it slightly
  • Dropping it into ice cold water
  • A reverse field of appropriate strength
A current loop placed in a magnetic field behaves like a
  • Magnetic dipole
  • Magnetic substance
  • Magnetic pole
  • All are true
A magnet when placed perpendicular to a uniform field of strength 10–4 Wb/m2 experiences a maximum couple of moment 4 × 10–5 N/m. What is its magnetic moment
  • 0.4 A × m2
  • 0.2 A × m2
  • 0.06 A × m2
  • 0.04 A × m2
Weber/m2 is equal to
  • Volt
  • Henry
  • Tesla
  • All of these
Two magnets, each of magnetic moment ‘M’ are placed so as to form a cross at right angles to each other. The magnetic moment of the system will be
  • 2 M
  • √2 M
  • 0.5 M
  • M
Two like magnetic poles of strength 10 and 40 SI units are separated by a distance 30 cm. The intensity of magnetic field is zero on the line joining them
  • At a point 10 cm from the stronger pole
  • At a point 20 cm from the stronger pole
  • At the mid-point
  • At infinity
The intensity of magnetic field is H and moment of magnet is M. The maximum potential energy is
  • MH
  • 2 MH
  • 3 MH
  • 4 MH
0:0:1


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