A small bar magnet is placed with its north pole facing the magnetic north pole. The neutral points are located at a distance r from its centre. If the magnet is rotated by 180o, the neutral point shall be obtained at a distance of:
1. \(2r\)
2. \(\sqrt{2}r\)
3. \(2^{\frac{1}{3}}r\)
4. \(\frac{r}{2\sqrt{2}}\)
A neutral point is obtained at the centre of a vertical circular coil carrying current. The angle between the plane of the coil and the magnetic meridian is :
a) 0 (b) 45°
(c) 60° (d) 90°
A magnet of magnetic moment M is situated with its axis along the direction of a magnetic field of strength B. The work done in rotating it by an angle of 180o will be
(1) -MB
(2) +MB
(3) 0
(4) +2MB
A long magnetic needle 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:
1.
2.
3.
4. M, m
Two identical thin bar magnets each of length l and pole strength m are placed at the right angle to each other with the north pole of one touching south pole of the other. The magnetic moment of the system is :
1. ml
2. 2ml
3.
4.
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
1. 2.4N 2. 1.2N
3. 0.6N 4. 0.3N
Two equal bar magnets are kept as shown in the figure. The direction of the resultant magnetic field, indicated by arrowhead at the point P is: (approximately)
1. | 2. | ||
3. | 4. |
Two similar bar magnets P and Q, each of magnetic moment M, are taken. If P is cut along its axial line and Q is cut along its equatorial line, all the four pieces obtained have:
1. | equal pole strength |
2. | magnetic moment M/4 |
3. | magnetic moment M/2 |
4. | magnetic moment M |
A dip needle in a plane perpendicular to magnetic meridian will remain
(1) Vertical
(2) Horizontal
(3) In any direction
(4) At an angle of dip to the horizontal
If the angles of dip at two places are 30o and 45o respectively, then the ratio of horizontal components of earth's magnetic field at the two places will be:
(Assume net magnetic field to be equal at the two places)
1. √3 : √2
2. 1 : √2
3. 1 : √3
4. 1 : 2
The earth's magnetic field at a certain place has a horizontal component 0.3 Gauss and the total strength 0.5 Gauss. The angle of dip is
(1)
(2)
(3)
(4)
At a certain place, the horizontal component B0 and the vertical component V0 of the earth's magnetic field are equal in magnitude. The total intensity at the place will be
1. 2.
3. 4.
Two bar magnets with magnetic moments 2 M and M are fastened together at right angles to each other at their centres to form a crossed system, which can rotate freely about a vertical axis through the centre. The crossed system sets in earth’s magnetic field with magnet having magnetic moment 2M making an angle with the magnetic meridian such that
(a) (b)
(c) (d)
The angle of dip at a certain place is 30o. If the horizontal component of the earth’s magnetic field is H, the intensity of the total magnetic field is
1. 2.
3. 4.
A magnet is suspended in such a way that it oscillates in the horizontal plane. It makes 20 oscillations per minute at a place where dip angle is 30o and 15 oscillations per minute at a place where dip angle is 60o. The ratio of total earth's magnetic field at the two places is:
1.
2.
3. 4:9
4.
A bar magnet A of magnetic moment MA is found to oscillate at a frequency twice that of magnet B having identical size as magnet A, of magnetic moment MB when placed in a vibrating magneto-meter. We may say that
(1)
(2) MA = 8MB
(3) MA = 4MB
(4) MB = 8MA
A magnet of magnetic moment M oscillating freely in earth's horizontal magnetic field makes n oscillations per minute. If the magnetic moment is quadrupled and the earth's field is doubled, the number of oscillations made per minute would be
1. 2.
3. 4.
Two identical short bar magnets, each having magnetic moment M, are placed a distance of 2d apart with axes perpendicular to each other in a horizontal plane. The magnetic induction at a point midway between them is
(a) (b)
(c) (d)
The basic magnetization curve for a ferromagnetic material is shown in the figure. Then, the value of relative permeability is highest for the point :
1. P
2. Q
3. R
4. S
A superconductor exhibits perfect :
(1) Ferrimagnetism
(2) Ferromagnetism
(3) Paramagnetism
(4) Diamagnetism
Among the following properties describing diamagnetism identify the property that is wrongly stated
1. Diamagnetic material do not have permanent magnetic moment
2. Diamagnetism is explained in terms of electromagnetic induction
3. Diamagnetic materials have a small positive susceptibility
4. The magnetic moment of individual electrons neutralize each other
If a magnet is suspended at an angle 30o to the magnetic meridian, it makes an angle of 45o with the horizontal. The real dip is
(a)
(b)
(c)
(d)
The true value of angle of dip at a place is 60o, the apparent dip in a plane inclined at an angle of 30o with magnetic meridian is
(1)
(2)
(3)
(4)None of these
Two magnets A and B are identical and these are arranged as shown in the figure. Their length is negligible in comparison to the separation between them. A magnetic needle is placed between the magnets at point P which gets deflected through an angle under the influence of magnets. The ratio of distance d1 and d2 will be:
1.
2.
3.
4.
Two short magnets of equal dipole moments M are fastened perpendicularly at their centres (figure). The magnitude of the magnetic field at a distance d from the centre on the bisector of the right angle is :
1.
2.
3.
4.
The variation of magnetic susceptibility with temperature for a diamagnetic substance is best represented by
1.
2.
3.
4.
The relative permeability of a ferromagnetic substance varies with temperature (T) according to the curve:
1. A
2. B
3. C
4. D
The variation of the intensity of magnetisation (I) with respect to the magnetising field (H) in a diamagnetic substance is described by the graph
1. OD 2. OC
3. OB 4. OA
If be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip is given by
(1)
(2)
(3)
(4)
The magnetic susceptibility is negative for
1. paramagnetic material only
2. ferromagnetic material only
3. paramagnetic and ferromagnetic materials
4. diamagnetic material only
The following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic dipole. Which configuration has the highest net magnetic dipole moment?
1. | 2. | ||
3. | 4. |
A magnetic needle suspended parallel to a magnetic field requires J of work to turn it through . The torque needed to maintain the needle in this position will be
1. J
2. 3 J
3. J
4. 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?
1. C is of a diamagnetic material
2. D is of a ferromagnetic material
3. A is of a non-magnetic material
4. B is of a paramagnetic material
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:
1. | zero. |
2. | directed along with OP. |
3. | directed along with PO. |
4. | 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
1. repelled by both the poles
2. repelled by the north pole and attracted by the south pole
3. attracted by the north pole and repelled by the south pole
4. attracted by both the poles
A bar magnet having a magnetic moment of is free to rotate in a horizontal plane. A horizontal magnetic field exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction from the field is
(a) 0.6 J (b) 12 J
(c) 6 J (d) 2 J
Curie temperature is the temperature above which -
1. ferromagnetic material becomes paramagnetic material
2. paramagnetic material becomes diamagnetic material
3. paramagnetic material becomes ferromagnetic material
4. ferromagnetic material becomes diamagnetic material
Domain formation is the necessary feature of :
(1) ferromagnetism (2) diamagnetism
(3) paramagnetism (4) all of these
The magnetic susceptibility of a paramagnetic substance at -73C is 0.0060, then its value at -173C will be
1. 0.0030
2. 0.0120
3. 0.0180
4. 0.0045
The magnetic dipoles in a diamagnetic material are represented, for three situations. The three situations differ in the magnitude if a magnetic field applied to the material. In which situation the magnetisation of the material is the greatest :
1. A
2. B
3. C
4. equal in A,B and C
An iron rod of length L and magnetic moment M is bent in the form of a semicircle. Now its magnetic moment will be
1. M
2.
3.
4.
Time period of a freely suspended magnet does not depend upon
1. length of the magnet
2. pole strength of the magnet
3. horizontal component of earth's magentic field
4. length of the suspension thread
Relative permeability of iron is 5500, then its magnetic suceptibility will be -
1. 5501
2. 5499
3.
4. none of these
A current carrying coil is placed with its axis perpendicular to N-S direction. Let horizontal component of earth's magnetic field be and magnetic field inside the loop be H. If a magnet is suspended inside the loop, it makes angle with H. Then
1.
2.
3.
4.