CBSE Questions for Class 12 Medical Physics Magnetism And Matter Quiz 8 - MCQExams.com

In the above figure, tube A contains copper fillings and tube B contains aluminum fillings. If a strong magnet is brought close to the two tubes as shown in the figure, then 
(A) Centre of gravity of the tube A move towards the right
(B) Centre of gravity of tube B move towards the right
396836.JPG
  • Only A is true
  • Only B is true
  • Both A and B are true
  • Neither A nor B is true
The force experienced by a pole of strength 200 A m placed along a perpendicular bisector, 20 cm away from the centre of a bar magnet of length 5 cm and pole strength 200 A m is _____ N.
  • 350 x $$10^{-9}$$
  • 375 x $$10^{-4}$$
  • 400 x $$10^{-4}$$
  • 325 x $$10^{-4}$$
Alloys of ferromagnetic materials ___________.
  • are always ferromagnetic in nature
  • need not be ferromagnetic in nature
  • are always diamagnetic in nature
  • are always antiferromagnetic in nature
The product of pole strengths of two magnetic poles separated by a distance is 100 $$A^2m^2$$ and the force between them is 20 N. Find the force if the poles are replaced by another pair of poles whose product of the pole strengths is 320 $$A^2m^2$$ and are maintained at the same distance
  • 12 N
  • 48 N
  • 52 N
  • 64 N
A paramagnetic substance when placed in an externally applied non-uniform magnetic field tends to ___________.
  • increase the applied field
  • decrease the applied field
  • vary the applied field
  • change the applied field
A bar magnet of dipole moment M is initially perpendicular to a magnetic field of intensity B. The angle by which the magnet should be rotated so that the torque acting on it is half the maximum torque is ______
  • $$30^0$$
  • $$45^0$$
  • $$60^0$$
  • $$90^0$$
An emf is induced in an axle of a moving train, due to _____
  • The horizontal component of the earth's magnetic field
  • The vertical component of the earth's magnetic field
  • Both 1 and 2
  • None of the above
Magnetism is a property present in ___________.
  • Only a few materials
  • Only ferromagnetic material
  • Only paramagnetic material
  • All materials
Magnetic lines of force due to a current in a circular conductor are
  • Parallel to the plane of the coil.
  • Perpendicular to the plane of the coil at the centre only.
  • Perpendicular to the plane of the coil everywhere.
  • Parallel to the plane of the coil at the centre only.
Domain formation is the necessary feature of 
  • ferromagnetism
  • diamagnetism
  • paramagnetism
  • all of these
Liquid oxygen remains suspended between two pole forces of a magnet because it is:
  • diamagnetic
  • paramagnetic
  • ferromagnetic
  • antiferromagnetic
The magnetic susceptibility of an ideal diamagnetic substance is
  • -1
  • 0
  • +1
  • $$\infty$$
Which one of the following statement is not correct about the magnetic field?
  • Inside the magnet the linesgo from north pole to south pole of the magnet
  • Tangents, to the magnetic lines give the direction of the magnetic field
  • The magnetic lines form a closed loop
  • Magnetic lines of force do not cut each other
A coil having 200 turns each of area 0.2 $$m^2$$ is kept in a magnetic field whose induction changes from 0.8 T to 1.2 T in 2s. The induced emf is _____V.
  • 8
  • 2
  • 12
  • 20
 Identify the incorrect statement from the following.
  • The temperature of the magnet is increased its molecules vibrate more violently.
  • Magnetic strength of a magnet decreases with increasing temperature.
  • $$760^o$$C is the Curie point of iron.
  • None
Mark the correct difference between a permanent magnet and an electromagnet.
  • Permanent magnet does not require any external electric supply to produce the field. But their magnetic field is normally weaker than that of an electromagnet.
  • Hence, permanent magnets are relatively bulky in size compared to electromagnets.
  • The applications of permanent magnet in the field of engineering are quite limited.
  • All
A strong bar magnet placed vertically above a horizontal wooden board. The magnetic lines of force will be
  • only in horizontal plane around the magnet.
  • only in vertical plane around it magnet.
  • in horizontal as well as vertical plane around the magnet.
  • in all the planes around the magnet.
Which of the following materials which lack permanent magnetic dipoles ?
  • diamagnetic
  • ferromagnetic
  • semimagnetic
  • none of the above
The temperature, at which a ferromagnetic material entirely loses its magnetic properties, is referred as
  • non magnetic point
  • curie point
  • van revolt point
  • none
Why the applications of permanent magnet in the field of engineering are quite limited?
  • The field of these magnets are not everlasting.
  • They also lose their magnetism, if they get subjected to physical shock or vibration.
  • Their magnetic field is normally weaker.
  • All
Why is an electromagnet more advantageous?
  • It produces a strong magnetic field
  • The magnitude of the magnetic field can be easily changed
  • Reversing the current changes the polarity of the magnet
  • All of the above
Inside the magnet, the direction of field lines is from
  • north to south pole
  • south to north pole
  • depends on position on the earth
  • none
A piece of material moves very slowly towards a pole of magnet. The material must be _____________.
  • Diamagnetic
  • Ferromagnetic
  • Paramagnetic
  • Ferrimagnetic
A magnetic substance is kept in a magnetic field, it will be thrown out of the field if it is a __________ substance.
  • paramagnetic
  • ferromagnetic
  • diamagnetic
  • antiferromagnetic
If the magnet is cut into four equal parts such that their lengths and breadths are equal. Pole strength of each part is:
  • m
  • m/2
  • m/4
  • m/8
Two isolated point poles of strength $$30 \ Am^{2}$$ and $$60 \ Am^{2}$$ are placed at a distance of $$0.3\ m$$. The force of repulsion is:
  • $$\displaystyle 2\times { 10 }^{ -3 }N$$
  • $$\displaystyle 2\times { 10 }^{ -4 }N$$
  • $$\displaystyle 2\times { 10 }^{ 5 }N$$
  • $$\displaystyle 2\times { 10 }^{ -5 }N$$
Which of the following is true regarding dimagnetic substances (symbols have their usual meaning)?
  • $${ \mu }_{ r }>1,{ \chi }_{ m }>1$$
  • $${ \mu }_{ r }>1,{ \chi }_{ m }<1$$
  • $${ \mu }_{ r }<1,{ \chi }_{ m }<0$$
  • $${ \mu }_{ r }<1,{ \chi }_{ m }>0$$
If the liquid in a U - tube rises to high level in the limb placed between poles of an electromagnet, then the liquid is:
  • non - magnetic
  • diamagnetic
  • paramagnetic
  • ferromagnetic
The magnetic susceptibility is negative for:
  • diamagnetic material only
  • paramagnetic material only
  • ferromagnetic material only
  • paramagnetic and ferromagnetic materials
Two short bar magnets with magnetic moments $$400\ abA$$$$\displaystyle { cm }^{ 2 }$$ and $$800\ abA$$$$\displaystyle { cm }^{ 2 }$$ are placed with their axis in the same straight line with similar poles facing each other and with their centres at $$20\ cm$$ apart from each other. Then the force of repulsion is:

Disclaimer: No option as $$0.08\ dyne$$ was given in the original paper.
  • $$12\ dyne$$
  • $$6\ dyne$$
  • $$0.08\ dyne$$
  • $$150\ dyne$$
The strength of the magnetic field of an electromagnet :
  • is always greater than that of a permanent magnet
  • is always less than that of a permanent magnet
  • can be adjusted
  • none of the above
Once the applied electric current is removed, the electromagnet :
  • retains its magnetism
  • loses its magnetism
  • gets magnetized in opposite direction
  • none of the above
All of the following magnets pictured have magnetic field lines like the ones pictured in the diagram above. For which one are the poles correctly labeled?
498276_dd6debcc14ee4c2d9237753749a17a18.png
A bar magnet has a coercivity of $$\displaystyle 4\times { 10 }^{ 3 }{ Am }^{ -1 }$$. It is placed inside a solenoid of length $$12\ cm$$ having 60 turns in order to demagnetize it, the amount of current that should be passed through the solenoid is:
  • $$16\ A$$
  • $$8A\ $$
  • $$4\ A$$
  • $$2\ A$$
Superconducting metal in superconducting state relative permeability of
  • zero
  • one
  • negative
  • more than one
Identify which is not a property of a ferromagnetic material.
  • It contains magnetic domains.
  • It has magnetic atoms.
  • It can become a permanent magnet.
  • It can be magnetized by a magnetic field.
  • It contains aluminum
The material used for permanent magnet has:
  • low retentivity, high coercivity
  • high retentivity, low coercivity
  • high retentivity, high coercivity
  • low retentivity, low coercivity
The magnet is strongest near the
  • Poles of the magnet
  • Ends of the magnet
  • Centre of the magnet
  • One quarter point from the poles of the magnet
Choose the correct statement for the following
  • Magnetic lines give direction of magnetic field while electric field lines do not
  • Electric lines give direction of electric field while magnetic field lines do not
  • Electric lines of force are closed curves but not magnetic lines of force
  • Magnetic field lines are closed curved but electric field lines are not
Which of the following can be used to lift giant industrial machines?
  • electromagnets
  • permanent magnets
  • both A and B
  • none of the above
The distance between two magnetic poles is doubled and their pole-strength is also doubled. The force between them
  • Increases to four times
  • Decreases by half
  • Remains unchanged
  • Increases to two times
The space around the magnet in which another magnetic pole placed experiences a magnetic force is _________.
  • Magnetic field
  • Magnetic moment
  • Polarized space
  • None of the above
The magnetic lines of force due to a bar magnet are
  • Curved lines
  • Curved closed loops
  • Concentric circles
  • Parallel and straight
State True or False.
Magnetic lines of force are curved lines.
  • True
  • False
The magnetic induction due to short bar magnet on its axial line at a distance '$$d$$' is '$$B$$'. What is the magnetic induction due to the same bar magnet on the same line at a distance (a) $${d}/{4}$$?    (b) $${4d}/{5}$$?
  • (a) $$32 B$$       (b) $${125}/{64} B$$
  • (a) $$64 B$$       (b) $${125}/{64} B$$
  • (a) $$32 B$$       (b) $${125}/{32} B$$
  • (a) $$64 B$$       (b) $${125}/{32} B$$
Two magnetic monopoles are kept apart by a distance '$$d$$'. The magnetic force acting on each pole is '$$F$$'. How much percentage must the distance between the magnetic poles be changed so that the magnetic force acting on each pole be $$4F$$.
  • Decreases by $$50$$%
  • Decreases by $$20$$%
  • Increased by $$50$$%
  • Increased by $$20$$%
The variation of magnetic susceptibility with the temperature of a ferromagnetic material can be ploted as :
Which of the following is represented by the area enclosed by a hysteresis loop (B-H curve) ?
  • Permeability
  • Retentivity
  • Heat energy lost per unit volume in the sample
  • Susceptibility
Choose the correct statement(s) from the following
  • At a neutral point, there cannot be any lines of force
  • Magnetic lines of force exist inside a magnetised material
  • Soft iron pieces are used as magnetic keepers
  • The magnetic moment of a magnet decreases on bending it into a semicircle
Two magnetic poles each of magnetic pole strength $$16 A m$$ are placed at a distance of $$2 m$$ apart. Find magnetic force acting on each pole.
  • $$4 \times {10}^{-7} N$$
  • $$16 \times {10}^{-7} N$$
  • $$32 \times {10}^{-7} N$$
  • $$64 \times {10}^{-7} N$$
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