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Magnetism Mcq
Quiz 9
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Q.1
The periods of oscillation of two magnets in the same field in the ratio 2:If their moment of inertia are equal, ratio of their magnetic moments is
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a) 1 : 2
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b) 1 : 4
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c)2 : 1
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d)4 : 1
Explanation
Answer:(b)
Q.2
When a magnet marked N - s is suspended in a horizontal position, so that it is free to rotate, the pole marked N shall point towards
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a) south pole of earth's magnet
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b) north pole of earth's magnet
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c) geographic N pole
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d) geographic S pole
Explanation
Answer: (a)
Q.3
The relative permeability of iron is of the order of ...
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a)1
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b) 104
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c)zero
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d)10-4
Explanation
Answer: (b)
Q.4
Curie's law state that
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a) magnetic susceptibility is inversely proportional to the absolute temperature
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b) magnetic susceptibility is inversely proportional the square root of the absolute temperature
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c)magnetic susceptibility is directly proportional to the absolute temperature
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d)magnetic susceptibility is independent of temperature
Explanation
Answer: (a)
Q.5
The permanent magnetic moment of atoms or molecules of a diamagnetic material is
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a) small
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b) large
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c)negative
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d)zero
Explanation
Answer:(d)
Q.6
The relation between magnetic susceptibility χm and relative permeability µr, is
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a) χm=µr
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b) χm - 1=µr
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c) χm + 1=µr
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d) χm=1- µr
Explanation
Answer: (c)
Q.7
If M is magnetic moment developed in the material having volume V, then intensity of magnetization is given by the expression
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a)MV
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b) M / V
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c)M √V
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d)M / √V
Explanation
Answer: (b)
Q.8
The relation between B, H and I in S.I. unit is
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a) B=µo ( H + I)
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b) B=H + 4π I
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c)H=µo ( B + I)
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d)none of these
Explanation
Answer: (a)
Q.9
A temparary magnet is made of
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a) cast iron
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b) steel
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c)soft iron
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d)stainless steel
Explanation
Answer:(c)
Q.10
Water is..
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a) diamagnetic
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b) paramagnetic
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c) ferromagnetic
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d) none of these
Explanation
Answer: (a)
Q.11
The relative permeability of a medium is 0.What is its magnetic susceptibility?
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a)0.925
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b) -0.925
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c)1.075
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d)-1.075
Explanation
use formula χm + 1=µrAnswer: (b)
Q.12
The moment of magnet ( 15cm ×2cm × 1cm) is 1.2 A-mWhat is its intensity of magnetization ?
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a) 4 × 104 A/m
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b) 2 × 104 A/m
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c)104 A/m
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d)none
Explanation
Intensity of magnetization=magnetic moment / volumeAnswer: (a)
Q.13
As magnetizing field on a ferromagnetic material is increased, its permeability..
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a) increases
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b) decreases
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c)remains constant
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d)can not say
Explanation
Answer:(b)
Q.14
Magnetic field do not interact with
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a) stationary charge
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b) moving electric charges
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c) stationary permanent magnet
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d) moving permanent magnets
Explanation
Answer: (a)
Q.15
Two identical thin bar magnets each of length l and pole strength m are placed at right angles to each other, with north pole of one touching south pole of the other , then the magnetic moment of the system is
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a)ml
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b) 2ml
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c)√2 ml
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d)ml/2
Explanation
Answer: (c)
Q.16
The ratio of magnetic potentials due to magnetic dipole in the end position to that in broad side on position for the same distance from it is
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a) zero
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b) ∞
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c)1
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d)2
Explanation
Answer: (b)
Q.17
A thin bar magnet of length 2l and breadth 2b pole strength p and magnetic moment M is divided into four equal parts with length and breadth of each part being half of original magnet. Then the pole strength of each part is
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a) p
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b) p/2
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c)p/4
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d)2p
Explanation
Answer:(b)
Q.18
In above question, magnetic moment of each part is
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a) M/4
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b) M
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c) M/2
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d) 2M
Explanation
Answer: (a)
Q.19
A circular loop is replaced by an equivalent magnetic dipole. then the equivalent magnetic dipole has a constant
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a)pole strength m of each pole
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b) length 2l of dipole
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c)product of m and 2l
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d)all of the above
Explanation
Answer: (c)
Q.20
In a bar magnet, the magnetic field lines...
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a) are not present
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b) depend upon the cross-section area of the magnet
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c)go from N-pole to s pole
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d)go from S-pole to N-pole
Explanation
Answer: (d)
Q.21
A magnetic needle hang using silk fiber oscillates in earth's magnetic field. If the temperature of this needle is raised beyond the curie temperature of the material of the needle, then [ CBSEB 2007]
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a)the periodic time of the oscillation will increase
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b) the periodic time of the oscillation will decrease
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c)the periodic time of the oscillation will not change
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d)the needle will stop oscillating
Explanation
Above Curie temperature the magnetic needle will become an ordinary piece of iron, so it will stop oscillating as no torque acts on it Answer:(d)
Q.22
Which of the following has negative magnetic susceptibility?
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a) Ferromagnetic substance
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b) Paramagnetic substance
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c) Diamagnetic substance
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d) None of above
Explanation
Answer: (c)
Q.23
Which of the following has negative magnetic susceptibility
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a)Ferromagnetic substance
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b) Paramagnetic substance
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c)Diamagnetic substance
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d)None of the above
Explanation
Answer: (c)
Q.24
Magnetization intensity for vacuum is ... [GSEB 2008]
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a) negative
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b) positive
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c)∞
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d)0
Explanation
Answer: (d)
Q.25
A bar magnet with dipole moment m is kept perpendicular to a uniform magnetic field B. If it is released in this situation and it rotates and makes an angle θ with the magnetic field, then the work done in this process is ....
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a)MB
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b)MB cosθ
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c)MBsinθ
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d)MB(1-cosθ)
Explanation
Answer:(b)
Q.26
The earth's magnetic field in a closed iron box is .... than the magnetic field outside the box
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a) more
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b) less
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c) equal
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d) zero
Explanation
Answer: (b)
Q.27
A bar magnet has magnetic dipole moment M. Its initial position is parallel to a uniform magnetic field. In this position, the torque and force acting on its are .....
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a)0,0
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b) M × B and MB
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c)M . B and MB
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d)None of these
Explanation
Answer: (a)
Q.28
If we place a bar magnet in the magnetic meridian with its north pole towards geographic north, the neutral point will be
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a) on the axis of magnet
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b) on the equatorial line of magnet
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c)at 45° with axial line
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d)at 45° with equatorial line
Explanation
Answer: (b)
Q.29
A bar magnet is suspended with unspun thread. It lies in the magnetic meridian. the upper end of the thread is turned through 150°. It turns the magnet by 30° with the magnetic meridian. through what angle should the upper end of thread be turned to rotate the magnet through 90°
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a)360°
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b) 330°
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c)300°
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d)270°
Explanation
First case:twist in thread δ1=150-30=120°Now restoring torque τ1=kδ1=MBsin30°Second case: τ2=kδ2=MBsin90° By taking ratio δ2 /δ1=sin90/sin30=2 ∴ δ2=2δ1=240° ∴ thread must be turned by 240+90=330° Answer:(b)
Q.30
Which of the following does not represent the unit for magneticdipole moment?
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a) Am2
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b) T/J
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c) J/T
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d) Nm/T
Explanation
Answer: (b)
0 h : 0 m : 1 s
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