JEE Questions for Physics Magnetism And Matter Quiz 6 - MCQExams.com

Three similar bar magnets are placed to form an equilateral triangle as shown in Fig. The magnetic moment of each magnet is M. What is the magnetic moment of the system?
Physics-Magnetism and Matter-78032.png
  • M
  • Zero
  • 2 M
  • M/2
A uniform magnetic needles is suspended from its centre by a thread. Its upper end is now loaded with a mass of 50 milligram, and the needle becomes horizontal. If the strength of each pole is 98.1 ab amp-cm and g = 981 cm/s2, then the vertical component of earth’s magnetic induction is
  • 0.50 gauss
  • 0.25 gauss
  • 0.005 gauss
  • 0.05 gauss
A magnet 20 cm long with its poles concentrated at its ends is placed vertically with its north pole on the table. At a point due 20 cm south (magnetic) of the pole, a neutral point is obtained. If H = 0.3 gauss, then the pole strength of the magnet is approximately
  • 185 ab-amp cm
  • 185 amp.m
  • 18.5 ab-amp cm
  • 18.5 amp m
An iron rod of length L and magnetic moment M is bent in the form of a semicircle. Now its magnetic moment will be
  • M
  • 2)
    Physics-Magnetism and Matter-78036.png

  • Physics-Magnetism and Matter-78037.png
  • Mπ
Unit of magnetic flux density (or magnetic induction) is
  • Tesla
  • Weber/metre2
  • Newton/ampere-metre
  • All of these
Magnetic intensity for an axial point due to a short bar magnet of magnetic moment M is given by

  • Physics-Magnetism and Matter-78039.png
  • 2)
    Physics-Magnetism and Matter-78040.png

  • Physics-Magnetism and Matter-78041.png

  • Physics-Magnetism and Matter-78042.png
A magnetic dipole is placed in a uniform magnetic field. The net magnetic force on the dipole
  • Is always zero
  • Depends on the orientation of the dipole
  • Can never be zero
  • Depends on the strength of the dipole
If a magnet of pole strength m is divided into four parts such that the length and width of each part is half that of initial one, then the pole strength of each part will be
  • m/4
  • m/2
  • m/8
  • 4m
The distance of two points on the axis of a magnet from its centre is 10 cm and 20 cm respectively. The ratio of magnetic intensity at these points is 12.5 : 1. The length of the magnet will be
  • 5 cm
  • 25 cm
  • 10 cm
  • 20 cm
Ratio of magnetic intensities for an axial point and a point on broad side-on position at equal distance d from the centre of magnet will be or The magnetic field at a distance d from a short bar magnet in longitudinal and transverse positions are in the ratio
  • 1 : 1
  • 2 : 3
  • 2 : 1
  • 3 : 2
The magnetism of magnet is due to
  • The spin motion of electron
  • Earth
  • Pressure of big magnet inside the earth
  • Cosmic rays
The magnetic field at a point x on the axis of a small bar magnet is equal to the field at a pointy on the equator of the same magnet. The ratio of the distance of x and y from the centre of the magnet is
  • 2–3
  • 2–1/3
  • 22
  • 21/3
A magnet of magnetic moment 20 C.G.S. units is freely suspended in a uniform magnetic field of intesity 0.3 C.G.S. units. The amount of work done in deflecting it by an angle of 30° in C.G.S. units is
  • 6
  • 2)
    Physics-Magnetism and Matter-78049.png

  • Physics-Magnetism and Matter-78050.png
  • 3
A bar magnet having centre O has a length of 4 cm. Point P1 is in the broad side-on and P2 is in the end side-on position with OP1 = OP2 = 10 metres. The ratio of magnetic intensities H at P1 and P2 is
  • H1 : H2 = 16 :100
  • H1 : H2 = 1 : 2
  • H1 : H2 = 2 :1
  • H1 : H2 = 100 :16
The magnetic field due to a short magnet at a point on its axis at distance X cm from the middle point of the magnet is 200 gauss. The magnetic field at a point on the neutral axis at a distance X cm from the middle of the magnet is
  • 100 gauss
  • 400 gauss
  • 50 gauss
  • 200 gauss
Which of the following is the most suitable material for making permanent magnet
  • Steel
  • Soft iron
  • Copper
  • Nickel
In the case of bar magnet, lines of magnetic induction
  • Start from the north pole and end at the south pole
  • Run continuously through the bar and outside
  • Emerge in circular paths from the middle of the bar
  • Are produced only at the north pole like rays of light from a bulb
A magnet of length 0.1 m and pole strength 10–4 Am is kept in a magnetic field of 30 WB/m2 at an angle 30°. The couple acting on it is…. × 10–4 Nm.
  • 7.5
  • 3.0
  • 1.5
  • 6.0
The field due to a magnet at a distance R from the centre of the magnet is proportional to
  • R2
  • R3
  • 1/R2
  • 1/R3
A uniform magnetic field parallel to the plane of the paper exists in space initially directed from left ro right. When a bar of soft iron is placed in the field paralled to it, the lines of force passing through it will be represented by
Physics-Magnetism and Matter-78054.png
  • Figure (A)
  • Figure (B)
  • Figure (C)
  • Figure (D)
Points A and B are situated perpendicular to the axis of a 2 cm long bar magnet at large distances X and 3X from its centre on opposite sides. The ratio of the magnetic fields at A and B will be approximately equal to
  • 1 : 9
  • 2 : 9
  • 27 : 1
  • 9 : 1
Two short magnets with their axes horizontal and perpendicular to the magnetic meridian are placed with their centres 40 cm east and 50 cm west of magnetic needle. It the needle remains undeflected, the ratio of their magnetic moments M1 : M2 is
  • 4 : 5
  • 16 : 25
  • 64 : 125
  • 2 : √5
If a bar magnet of magnetic moment M is freely suspended in a uniform magnetic field of strength B, the work done in rotating the magnet through an angle θ is
  • MB(1 – sin θ)
  • MB sin θ
  • MB cos θ
  • MB(1 – cos θ)
Two small bar magnets are placed in a line with like poles facing each other at a certain distance d apart. If the length of each magnet is negligible as compared to d, the force between them will be inversely proportional to
  • d
  • d2

  • Physics-Magnetism and Matter-78057.png
  • d4
A magnet of magnetic moment M is situated with its axis along the direction of a magnetic field of strength B. The work done is rotaing it by an angle of 180° will be
  • –MB
  • +MB
  • 0
  • +2MB
Two identical short bar magnets, each having magnetic moment of 10 Am2, are arranged such that their axial lines are perpendicular to each other and their centres be along the same straight line in a horizontal plane. If the distance between their centres is 0.2 m, the resultant magnetic induction at a point midway between them is (µ0 = 4π × 10–7 Hm–1)

  • Physics-Magnetism and Matter-78060.png
  • 2)
    Physics-Magnetism and Matter-78061.png

  • Physics-Magnetism and Matter-78062.png

  • Physics-Magnetism and Matter-78063.png
A bar magnet of length 10 cm and having the pole strength equal to 10–3 weber is kept in a magnetic field having magnetic induction (B) equal to 4 π × 10–3tesla. It makes an angle of 30° with the direction of magnetic induction. The value of the torque acting on the magnet is
  • 2π × 10–7N × m
  • 2 π × 10–5 N × m
  • 0.5 N × m
  • 0.5 × 102 N × m (µ0 =4 π × 10–7 weber/amp × m)
Magnetic field intensity is defined as
  • Magnetic moment per unit volume
  • Magnetic induction force acting on a unit magnetic pole
  • Number of lines of force crossing per unit area
  • Number of lines of force crossing per unit volume
If the magnetic flux is expressed in weber, then magnetic induction can be expressed in
  • Weber/m2
  • Weber/m
  • Weber-m
  • Weber-m2
A magnetic needle is kept in a non-uniform magnetic field. It experiences
  • A force and torque
  • A force but not a torque
  • A torque but not a force
  • Neither a torque nor a force
0:0:1


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