The figure illustrates how B , the flux density, inside a sample of unmagnetized ferromagnetic material varies with B 0 , the magnetic flux density, in which the sample is kept. For the sample to be suitable for making a permanent magnet -

OQ should be large and OR should be small

OQ should be small and OR should be large

A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It

will become rigid showing no movement

will stay in north-south direction only

will stay in east-west direction only

Curie temperature is the temperature above which:

Ferromagnetic material becomes paramagnetic material.

Paramagnetic material becomes diamagnetic material.

Paramagnetic material becomes ferromagnetic material.

Ferromagnetic material becomes diamagnetic material.

Above Curie temperature:

a ferromagnetic substance becomes paramagnetic.

a paramagnetic substance becomes diamagnetic.

a diamagnetic substance becomes paramagnetic.

a paramagnetic substance becomes ferromagnetic.

Physics - Magnetism Matter - Quiz-3

The variation of magnetic susceptibility $(χ)$ with temperature for a diamagnetic substance is best represented by

The variation of magnetic susceptibility $(χ)$ with absolute temperature T for a ferromagnetic material is

The relative permeability $(μ_{r})$ of a ferromagnetic substance varies with temperature (T) according to the curve

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A
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B
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C
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D

Some equipotential surfaces of the magnetic scalar potential are shown in the figure. The magnetic field at a point in the region is: (X-axis read in cm)

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$10^{- 4} T$
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$2 \times 10^{- 4} T$
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$0.5 \times 10^{- 4} T$
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None of these

The figure illustrates how B, the flux density, inside a sample of unmagnetized ferromagnetic material varies with B₀, the magnetic flux density, in which the sample is kept. For the sample to be suitable for making a permanent magnet -

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OQ should be large and OR should be small
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OQ and OR should both be large
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OQ should be small and OR should be large
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OQ and OR should both be small

The variation of the intensity of magnetisation (I) with respect to the magnetising field (H) in a diamagnetic substance is described by the graph

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OD
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OC
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OB
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OA

A current-carrying loop is placed in a uniform magnetic field in four different orientations, I, II, III & IV. The decreasing order of potential energy is:

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I > III > II > IV
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I > II >III > IV
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I > IV > II > III
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III > IV > I > II

A 250-turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85 $μ$ A and subjected to a magnetic field of strength o.85 T. Work done for rotating the coil by $180^{\circ}$ against the torque is

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9.1 $μ J$
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4.55 $μ J$
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2.3 $μ$ $J$
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1.5 $μ J$

If $θ_{1} a n d θ_{2}$ be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip $θ$ is given by

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$c o t^{2} θ = c o t^{2} θ_{1} + c o t^{2} θ_{2}$
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$\tan^{2} θ = \tan^{2} θ_{1} + \tan^{2} θ_{2}$
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$c o t^{2} θ = c o t^{2} θ_{1} - \tan^{2} θ_{2}$
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$\tan^{2} θ = \tan^{2} θ_{1} - \tan^{2} θ_{2}$

A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in the equilibrium state. The energy required to rotate it by $60^{\circ}$ is W. Now the torque required to keep the magnet in this new position is:

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$\frac{W}{\sqrt{3}}$
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$\sqrt{3} W$
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$\frac{\sqrt{3} W}{2}$
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$\frac{2 W}{\sqrt{3}}$

The magnetic susceptibility is negative for

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paramagnetic material only
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ferromagnetic material only
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paramagnetic and ferromagnetic materials
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diamagnetic material only

The following figures show the arrangement of bar magnet in different configurations. Each magnet has magnetic dipole moment m. Which configuration has the highest net magnetic dipole moment?

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(d)
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(b)
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(c)
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(a)

A bar magnet of length L and magnetic dipole moment M is bent in the form of an are as shown in figure. The new magnetic dipole moment will be

(1)M

(2)3M/π

(3)2/πM

(4)M/2

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1
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2
0%
3
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4

A magnetic needle suspended parallel to a

magnetic field requires $\sqrt{3}$ J of work to turn

it through $60 °$ . The torque needed to maintain

the needle in this position will be

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$2 \sqrt{3}$ J
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3 J
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$\sqrt{3}$ J
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$\frac{3}{2}$ J

There are four light-weight-rod samples; A, B, C, D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted:

(i) A is feebly repelled

(ii) B is feebly attracted

(iii) C is strongly attracted

(iv) D remains unaffected

Which one of the following is true?

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C is of a diamagnetic material
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D is of a ferromagnetic material
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A is of a non-magnetic material
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B is of a paramagnetic material

A short bar magnet of magnetic moment 0.4 JT^–1 is placed in a uniform magnetic field of 0.16 T. The magnet is in stable equilibrium when the potential energy is:

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– 0.64 J
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zero
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– 0.82 J
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– 0.064 J

A vibration magnetometer placed in a magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of 2s in earth's horizontal magnetic field of 24 $μ$ T. When a horizontal field is 18 $μ$ T is produced opposite to the earth's field by placing a current-carrying wire, the new time period of the magnet will be

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() 1s
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() 2s
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() 3s
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() 4s

Electromagnets are made of soft iron because soft iron has :

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low retentivity and high coercive force
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high retentivity and high coercive force
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low retentivity and low coercive force
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high retentivity and low coercive force

The magnetic moment of a diamagnetic atom is:

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much greater than one.
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one.
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between zero and one.
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equal to zero.

Two identical bar magnets are fixed with their centres at a distance d apart. A stationary charge Q is placed at P in between the gap of the two magnets at a distance D from the centre O as shown in the figure.

The force on the charge Q is:

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zero.
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directed along with OP.
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directed along with PO.
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directed perpendicular to the plane of the paper.

If a diamagnetic substance is brought near the north or the south pole of a bar magnet, it is

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repelled by both the poles
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repelled by the north pole and attracted by the south pole
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attracted by the north pole and repelled by the south pole
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attracted by both the poles

A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in the equilibrium state. The energy required to rotate it by 60^o is W. Now the torque required to keep the magnet in this new position is:

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$\frac{W}{\sqrt{3}}$
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$\sqrt{3} W$
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$\frac{\sqrt{3} W}{2}$
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$\frac{2 W}{\sqrt{3}}$

A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from

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the current source
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the magnetic field
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the lattice structure of the material of the rod
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the induced electric field due to the changing magnetic field.

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Practice Physics Quiz Questions and Answers

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Practice Physics Quiz Questions and Answers

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