50 questions · timed · auto-graded
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
| (a) 5 cm | (b) 25 cm | (c) 10 cm | (d) 20 cm |
(c) 10 cm
Curie temperature is the temperature above which
|
(a) A paramagnetic material becomes ferromagnetic |
|
(b) A ferromagnetic material becomes paramagnetic |
| (c) A paramagnetic material becomes diamagnetic |
|
(d) A ferromagnetic material becomes diamagnetic |
(b) A ferromagnetic material becomes paramagnetic
In a vibration magnetometer, the time period of a bar magnet oscillating in horizontal component of earth's magnetic field is 2 sec. When a magnet is brought near and parallel to it, the time period reduces to 1 sec. The ratio H/F of the horizontal component H and the field F due to magnet will be
| (a) 3 | (b) 1/3 |
(c) 
|
(d) 1/
|
(b) 1/3
Two short magnets placed along the same axis with their like poles facing each other repel each other with a force which varies inversely as
| (a) Square of the distance | (b) Cube of the distance |
| (c) Distance | (d) Fourth power of the distance |
(d) Fourth power of the distance
The magnetic moment of atomic neon is
| (a) Zero | (b) μB/2 | (c) μB | (d) 3μB/2 |
(a) Zero
Demagnetisation of magnets can be done by
| (a) Rough handling | (b) Heating |
| (c) Magnetising in the opposite direction | (d) All the above |
(d) All the above
A ferromagnetic material is heated above its curie temperature. Which one is a correct statement
| (a) Ferromagnetic domains are perfectly arranged |
| (b) Ferromagnetic domains becomes random |
| (c) Ferromagnetic domains are not influenced |
| (d) Ferromagnetic material changes itself into diamagnetic material |
(b) Ferromagnetic domains becomes random
If a diamagnetic substance is brought near north or south pole of a bar magnet, it is
| (a) Attracted by the poles |
| (b) Repelled by the poles |
|
(c) Repelled by the north pole and attracted by the south pole |
|
(d) Attracted by the north pole and repelled by the south pole |
(b) Repelled by the poles
The material of permanent magnet has
| (a) High retentivity, low coercivity | (b) Low retentivity, high coercivity |
| (c) Low retentivity, low coercivity | (d) High retentivity, high coercivity |
(d) High retentivity, high coercivity
The permanent magnet is made from which one of the following substances
| (a) Diamagnetic | (b) Paramagnetic | (c) Ferromagnetic | (d) Electromagnetic |
(c) Ferromagnetic
Temperature above which a ferromagnetic substance becomes paramagnetic is called
| (a) Critical temperature | (b) Boyle's temperature |
| (c) Debye's temperature | (d) Curie temperature |
(d) Curie temperature
The number of turns and radius of cross-section of the coil of a tangent galvanometer are doubled. The reduction factor K will be
| (a) K |
(b) 2K |
(c) 4K |
(d) K/4 |
(a) K
The time period of a bar magnet suspended horizontally in the earth's magnetic field and allowed to oscillate
| (a) Is directly proportional to the square root of its mass |
| (b) Is directly proportional to its pole strength |
| (c) Is inversely proportional to its magnetic moment |
| (d) Decreases if the length increases but pole strength remains same |
(a) Is directly proportional to the square root of its mass
At two places A and B using vibration magnetometer, a magnet vibrates in a horizontal plane and its respective periodic time are 2 sec and 3 sec and at these places the earth's horizontal components are HA and HB respectively. Then the ratio between HA and HB will be
| (a) 9 : 4 | (b) 3 : 2 | (c) 4 : 9 | (d) 2 : 3 |
(a) 9 : 4
Lines which represent places of constant angle of dip are called
| (a) Isobaric lines | (b) Isogonic lines | (c) Isoclinic lines | (d) Isodynamic lines |
(c) Isoclinic lines
In two separate experiments the neutral points due to two small magnets are at a distance of r and 2r in broad side-on position. The ratio of their magnetic moments will be
| (a) 4 : 1 | (b) 1 : 2 | (c) 2 : 1 | (d) 1 : 8 |
(d) 1 : 8
The line on the earth's surface joining the points where the field is horizontal is
| (a) Magnetic meridian | (b) Magnetic axis | (c) Magnetic line | (d) Magnetic equator |
(d) Magnetic equator
Intensity of magnetic field due to earth at a point inside a hollow steel box is
|
(a) Less than outside |
(b) More than outside | (c) Same | (d) Zero |
(d) Zero
A magnet of magnetic moment M is rotated through 360° in a magnetic field H, the work done will be
| (a) MH | (b) 2MH | (c) 2πMH | (d) Zero |
(d) Zero
For ferromagnetic material, the relative permeability (
, versus magnetic intensity (H) has the following shape
|
(a)
|
(b)
|
(c)
|
(d)
|
(d)
The X – 1/T graph for an alloy of paramagnetic nature is shown in Fig. The curie constant is, then
|
(a) 57 K |
(b) 2.8 |
(c) 570 K |
(d) 17.5 |
(a) 57 K
A curve between magnetic moment and temperature of magnet is
|
(a)
|
(b)
|
(c)
|
(d)
|
(c)
Two identical bar magnets with a length 10 cm and weight 50 gm-weight are arranged freely with their like poles facing in a inverted vertical glass tube. The upper magnet hangs in the air above the lower one so that the distance between the nearest pole of the magnet is 3mm. Pole strength of the poles of each magnet will be
|
(a) 6.64 amp × m |
(b) 2 amp × m |
(c) 10.25 amp × m |
(d) None of these |
(a) 6.64 amp × m
The given figure represents a material which is
|
(a) Paramagnetic |
(b) Diamagnetic |
(c) Ferromagnetic |
(d) None of these |
(b) Diamagnetic
A bar magnet of length 3 cm has points A and B along its axis at distances of 24 cm and 48 cm on the opposite sides. Ratio of magnetic fields at these points will be
|
(a) 8 |
(b) 1/2 |
(c) 3 |
(d) 4 |
(a) 8
A uniform magnetic field, parallel to the plane of the paper existed in space initially directed from left to right. When a bar of soft iron is placed in the field parallel to it, the lines of force passing through it will be represented by
(b) Figure (B)
Answer
The magnetic field lines due to a bar magnet are correctly shown in
|
(a)
|
(b)
|
(c)
|
(d)
|
(d)
For substances hysteresis (B - H) curves are given as shown in figure. For making temporary magnet which of the following is best.
|
(a)
|
(b)
|
(c)
|
(d)
|
(d)
The relative permeability is represented by mr and the susceptibility is denoted by c for a magnetic substance. Then for a paramagnetic substance
|
(a) mr < 1, c < 0 |
(b) mr < 1, c > 0 |
(c) mr > 1, c < 0 |
(d) mr > 1, c > 0 |
(d) mr > 1, c > 0
Two identical thin bar magnets each of length l and pole strength m are placed at right angle to each other with north pole of one touching south pole of the other. Magnetic moment of the system is
|
(a) ml |
(b) 2ml |
(c) |
(d) |
(c) 
An iron rod of volume 
and relative permeability 1000 is placed inside a long solenoid wound with 5 turns/cm. If a current of 0.5 A is passed through the solenoid, then the magnetic moment of the rod is
|
(a) 10 |
(b) 15 |
(c) 20 |
(d) 25 |
(d) 25 
Which of the following statements are true about the magnetic susceptibility 
of paramagnetic substance
|
(a) Value of |
|
(b) |
|
(c) |
|
(d) |
(d) 
A magnetic needle is made to vibrate in uniform field H, then its time period is T. If it vibrates in the field of intensity 4H, its time period will be
| (a) 2T | (b) T/2 | (c) 2/T | (c) 2/T |
(b) T/2
Time period for a magnet is T. If it is divided in four equal parts along its axis and perpendicular to its axis as shown then time period for each part will be
| (a) 4T | (b) T/4 | (c) T/2 | (d) T |
(c) T/2
Vibration magnetometer before use, should be set
| (a) In magnetic meridian | (b) In geographical meridian |
| (c) Perpendicular to magnetic meridian | (d) In any position |
(a) In magnetic meridian
The period of oscillation of a magnet in vibration magnetometer is 2 sec. The period of oscillation of a magnet whose magnetic moment is four times that of the first magnet is
| (a) 1 sec | (b) 4 sec | (c) 8 sec | (d) 0.5 sec |
(a) 1 sec
Two magnets of same size and mass make respectively 10 and 15 oscillations per minute at certain place. The ratio of their magnetic moments is
| (a) 4 : 9 | (b) 9 : 4 | (c) 2 : 3 | (d) 3 : 2 |
(a) 4 : 9
Time period of a freely suspended magnet does not depend upon
| (a) Length of the magnet |
| (b) Pole strength of the magnet |
| (c) Horizontal component of earth's magnetic field |
| (d) Length of the suspension thread |
(d) Length of the suspension thread
A cylindrical rod magnet has a length of 5 cm and a diameter of 1 cm. It has a uniform magnetisation of 5.30 × 103Amp/m3. What its magnetic dipole moment
(a) 1 
|
(b) 2.08
|
(c) 3.08
|
(d) 1.52
|
A small bar magnet A oscillates in a horizontal plane with a period T at a place where the angle of dip is 60o. When the same needle is made to oscillate in a vertical plane coinciding with the magnetic meridian, its period will be
(a) 
|
(b) T |
(c) 
|
(d) 2T |
Time period in vibration magnetometer will be infinity at
| (a) Magnetic equator | (b) Magnetic poles | (c) Equator | (d) At all places |
(b) Magnetic poles
Keeping dissimilar poles of two magnets of equal pole strength and length same side, their time period will be
| (a) Zero | (b) One second | (c) Infinity | (d) Any value |
(c) Infinity
Tangent galvanometer is used to measure
| (a) Steady currents | (b) Current impulses |
| (c) Magnetic moments of bar magnets | (d) Earth's magnetic field |
(a) Steady currents
Vibration magnetometer works on the principle of
| (a) Torque acting on the bar magnet |
| (b) Force acting on the bar magnet |
| (c) Both the force and the torque acting on the bar magnet |
| (d) None of these |
(a) Torque acting on the bar magnet
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
(a) 3
|
(b) 16 : 9
|
(c) 4 : 9 |
(d) 2
|
The time period of oscillation of a magnet in a vibration magnetometer is 1.5 seconds. The time period of oscillation of another magnet similar in size, shape and mass but having one-fourth magnetic moment than that of first magnet, oscillating at same place will be
| (a) 0.75 sec | (b) 1.5 sec | (c) 3 sec | (d) 6 sec |
(c) 3 sec
To compare magnetic moments of two magnets by vibration magnetometer, 'sum and difference method' is better because
|
(a) Determination of moment of inertia is not needed which minimises the errors |
| (b) Less observations are required |
| (c) Comparatively less calculations |
| (d) All the above |
(d) All the above
Vibration magnetometer is used for comparing
|
(a) Magnetic fields |
(b) Earth's field |
(c) Magnetic moments | (d) All of the above |
(d) All of the above
Magnetic moments of two bar magnets may be compared with the help of
| (a) Deflection magnetometer | (b) Vibration magnetometer |
| (c) Both of the above | (d) None of the above |
(c) Both of the above
A line passing through places having zero value of magnetic dip is called
|
(a) Isoclinic line |
(b) Agonic line |
(c) Isogonic line | (d) Aclinic line |
(d) Aclinic line
