PhysicsPhysics QuestionsMagnetism And Matter Questions for CBSE Class 12th

Magnetism And Matter Questions for CBSE Class 12th

  1. A rod of cross sectional area 10 cm 2 is placed with its length parallel to a magnetic field of intensity 1000 A/m the flux through the rod is 10 4 weber. Then the permeability of material of rod is
  2. A bar magnet of magnetic moment 5 Am 2 is suspended in a uniform magnetic field of strength 2T making an angle 60 o with the direction of the field. The potential energy of the magnet in that position is
  3. A magnetizing force of 360 Am –1 produces a magnetic flux density of 0.6 T in a ferromagnetic material. The susceptibility of the material is
  4. A bar magnets of length 1 cm has point A & B along its axis at distances of 12 cm & 24 cm on the opposite sides. Ratio of magnetic fields at these points will be:
  5. A solenoid has case of a material with relative permeability 500 and its winding carry a current of 1A. The number of turns of the solenoid is 5000 per meter. The magnetization of the material is nearly
  6. A short bar magnet of magnetic moment 0.8 JT -1 is placed in a uniform magnetic field of 0.32 T . The magnet is in stable equilibrium. When the potential energy is
  7. A thin magnetic iron rod of length 30 cm is suspended in a uniform magnetic field. Its time period of oscillation is T second. It is broken into three equal parts perpendicular to axis. The time period of oscillation of one part when suspended in the same magnetic field is
  8. Two magnetic poles one of which is three times as strong as the other exert on each other a force equal to 3 × 10 − 3 N when separated by a distance of 10cm . The strengths of each pole in Am
  9. Which of the following statements is correct about hard and soft magnetic materials
  10. Calculate the moment of couple required to keep a bar magnet of magnetic moment 2 × 10 2 Am 2 in a uniform field of induction 0.36 T at an angle of 30 o with the direction of uniform field.
  11. A bar magnet of moment 2 A-m 2 is free to rotate about a Vertical axis passing through its centre. The magnet is released form rest from east west direction. The K.E of the magnet as it takes north-south direction is (B H = 25 × 10 –6 T)
  12. The torque required to keep a magnet of length 20 cm at 30º to a uniform field is 2×10 –5 N-m. The magnetic force on each pole is
  13. At magnetic equator, total intensity of Earth’s magnetic field is I E and at poles it is I P . They are related as
  14. A thin bar magnet of length ‘l’ and magnetic moment ‘M’ is bent at the mid point so that the two parts are at right angles. The new magnetic length and magnetic moment are respectively
  15. The mass of an iron rod is 80 gm and its magnetic moment is 10 Am 2 . If the density of iron is 8 gm/c.c. Then the value of intensity of magnetization will be
  16. A bar magnet of magnetic moment 10 Am 2 has a cross sectional area of 2.5 × 10 –4 m 2 . If the intensity of magnetization of the magnet is 10 6 A/m, then the length of magnet is
  17. The line of force in a magnetic field represents the direction at each point that a magnetic needle placed at the point takes up. Do they also represent the direction of the force on a moving charge at each point?
  18. A dip needle lies initially in the magnetic meridian when it shows an angle of dip ‘ θ ‘ at the place. The dip circle is rotated through an angle ‘ x ‘ in the horizontal plane and then it shows an angle of dip θ 1 . Then, tan θ 1 / tan θ is
  19. If a magnet is suspended at an angle of 30 0 to the magnetic meridian the dip needle makes an angle of 60 0 with the horizontal. The real dip is
  20. The magnetic susceptibility of a material of a rod is 599, permeability of vacuum is 4 π × 10 − 7  henry/m . Absolute permeability of the material of the rod in henry per meter is
  21. A bar magnet made of steel has a magnetic moment of 1.2 A m 2 and a mass of 4.0 × 10 − 3 k g . If the density of steel is 12 .0 × 10 3 k g / m 3 . The intensity of magnetization of the magnet is × 10 6 Am -1
  22. The magnitude of magnetic field due to a dipole of magnetic moment 3.14 A m 2 at a point 1 m away from it in a direction making an angle of 60 0 with the dipole axis is 7 2 . n × 10 − 8 T . Then the value of ‘n ’ is
  23. An iron rod of volume 10 – 3 m 3 and relative permeability 1000 is placed as core in a solenoid with 10 turns/cm. If a current of 0.5 A is passed through the solenoid, then the magnetic moment of the rod will be:
  24. Two short bar magnets of length 1cm each have magnetic moments 1.20 Am 2 and 1.00 Am 2 , respectively. They are placed on a horizontal table parallel to each other with their N poles pointing towards the south. They have a common magnetic equator and are separated by a distance of 20.0cm. The value of the resultant horizontal magnetic induction at the mid-point O of the line joining their centers is close to (horizontal component of earth’s magnetic induction is 3.6 × 10 − 5 W b / m 2 )
  25. A bar magnet of magnetic moment 10  Am 2 has a cross sectional area of 2.5 × 10 − 4  m 2 . If the intensity of magnetization of the magnet is 10 6  A / m , the length of magnet is
  26. The magnet suspended in uniform magnetic field is heated so as to reduce its magnetic moment by 19%. By doing this, the time period of the magnet will
  27. Find the resultant magnetic moment for the following arrangement
  28. Some equipotential surfaces of the magnetic scalar potential are shown in the figure. Magnetic field at a point in the region is
  29. Two points A and B are located at distances 20cm and 30 cm from the centre of a short bar magnet on its axial line. The ratio of magnetic induction at A and B is
  30. The angle of dip at a place on the earth gives.
  31. A short bar magnet of magnetic moment 2 Am 2 and moment of inertia 6 × 10 2 kg / m 2 is freely suspended such that the magnetic axial line is in the direction of magnetic meridian. If the magnet is displaced by very small angle ( 3 o ), the angular acceleration is y × 10 – 6 rad / s 2 . Find y. (Magnetic induction of earth’s horizontal field = 4 × 10 – 4 T )
  32. A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by 60 0 is W. Now the torque required to keep the magnet in this new position is
  33. A dip needle is suspended at an angle of 30 o to the magnitude meridian. It makes an angle of 45 o with the horizontal. The real dip is
  34. Temperature above which Ferro magnetic substances becomes paramagnet is called
  35. When a piece of ferromagnetic substances is put in a uniform magnetic field, the flux density inside it is four times the flux density away from the piece. The magnetic permeability of the material is
  36. In figure, the magnetic needle has magnetic moment 6 . 7 x 10 – 2 A m 2 and moment of inertia 7 . 5 x 10 – 6 k g m 2 . It perform10 complete oscillations in 6.70s. What is the magnitude of the magnetic field? ………………. T.
  37. The figure gives experimentally measured B Vs H variation in a ferromagnetic material. The retentivity, co-ercivity respectively of the material are:
  38. In a certain place on the surface of earth, angle of dip in a vertical plane ‘P’ is 30 0 . At the same place, angle of dip in another vertical plane ‘Q’ which is perpendicular to the plane. ‘P’, is 60 0 . Then true angle of dip at that place is
  39. The ratio of magnetic moments of two short magnets which give null deflection in Tan B position at 24 cm and 18 cm from the centre of a deflection magnetometer is
  40. A paramagnetic substance of susceptibility 3 × 10 − 4 is placed in a magnetic field intensity of 6 × 10 − 4 A . m − 1 . Then the intensity of magnetization in the units of A − m − 1 is
  41. The susceptibility of magnesium at 300   K is 1.2 × 10 − 5 . The temp is 800 ×   t   K , the susceptibility is 1.8 × 10 − 5 . Then the value of ‘ t ‘ is
  42. The magnetic moment of the assumed dipole at the earth’s centre is 7 .0 × 10 22 A m 2 . The magnetic field B at the geomagnetic poles of the earth is P × 10 14 R 3 (The radius of earth is ‘R’), then the value of ‘P ’ is
  43. What is the resultant magnetic field induction at the third corner, if two unlike poles, each of strength ‘m’ are placed at the two corners of an equilateral triangle of side ‘a’
  44. M and 3 M are the magnetic dipole moments of two bar magnets which are joined to form a cross (+) structure. The combination is suspended freely in a uniform magnetic field . In the equilibrium position ,the angle between the bar magnet of magnetic moment M and the uniform magnetic field is
  45. A bar magnet of magnetic moment 2 A m 2 is free to rotate about a vertical axis passing through its centre. The magnet is released from rest from east-west position. Then the K.E of the magnet as it takes North-South position is ———– Take : B H = 25 μ T
  46. A magnetic dipole is placed under the effect of two magnetic fields inclined at 75 0 to each other one of the fields has a magnetic induction of 1 . 5 X 10 – 2 T . The magnet comes to rest at an angle of 30 ° with the direction of this field, the magnitude of the other field is
  47. When a short bar magnet is kept in TanA position on a deflection magnetometer, the magnetic needle Oscillates with a frequency ‘ f ‘ and the deflection produced is 45 0 . If the bar magnet is removed the frequency of oscillation of that needle is
  48. A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through 60 0 .What is the torque needed to maintain the needle in that position?
  49. A long bar magnet of time period T is cut in to four equal parts by cutting it perpendicular to both length and breadth. The time period of each part is
  50. A magnet is suspended in the magnetic meridian with un twisted wire. The upper end of the wire is rotated through 180 0 to deflect the magnet by 30 0 from magnetic meridian. Now this magnet is replaced by another magnet. Now the upper end of the wire is rotated through 270 0 to deflect the magnet 30 0 from the magnetic meridian. The ratio of the magnetic moments of the two magnets is
  51. The period of oscillation of a thin magnet at a place is T. When it is stretched to double its length and its pole strength is reduced to 1 4 of its initial value, then its period of oscillation is
  52. The magnetic potential at a point of a distance 40 cm from an isolated pole is 10 – 5 Tm . Then Magnetic moment in A m 2 is
  53. A short bar magnet of magnetic moment 20 Am 2 has a cross sectional area of 1 . 5 × 10 – 4 m 2 . If the intensity of magnetisation of the magnet is 10 5 A / m , the length of the magnet is
  54. When a thin bar magnet of magnetic moment M is bent in the form of S shape with the arms of equal length as shown in figure, then its new magnetic moment is
  55. Two short magnets of magnetic moment 1000 Am 2 are placed as shown at the corners of a square of side 10cm the net magnetic indication at P is
  56. A magnetic needle is oscillating in earth’s horizontal field B H with a time period of 0.5 sec. A dip needle of same magnetic dipole moment, mass and geometry oscillator in earth’s vertical field B V with a time period of 1 sec. Then angle of dip at that place is
  57. Which of the following magnetic materials have negative susceptibility ?
  58. Magnetic materials used for making permanent magnets (P) and magnets in a transformer (T) have different properties of the following, which property best matches for the type of magnet required?
  59. Two short bar magnets of equal dipole moment M are placed at angle 60º, the magnetic field at point P is (P is on the bisector of the angle between two magnets and d is very large)
  60. A ferromagnetic material is placed in an alternating magnetizing field. Area enclosed by the B-H curve is 8 c m 2 . If volume of the ferromagnetic material is 200 m 3 and 1 c m 2 area is equivalent to 10 – 5 Joule, then what is the total lost energy in 1000 cycles?
  61. At a point on the surface of earth true dip measured by a dip needle is 45 o . Now the plane of the dip needle is rotated through an angle of θ and the new dip measured by the dip needle is 60 o . Then θ is
  62. A paramagnetic substance in the form of a cube with sides 1 cm has a magnetic dipole moment of 20 × 10 − 3  J / T , when a magnetic intensity of 6 × 10 3   A / m is applied. Its magnetic susceptibility is
  63. The angle of dip at a certain place on earth is 30 o and the magnitude of earth’s horizontal component of magnetic field is 0.82G. Then vertical component of magnetic field at that place on earth is
  64. Two magnets have their lengths in the ratio 2 : 3 and their pole strengths in the ratio 3 : 4. The ratio of their magnetic moment is
  65. The force experienced by a magnetic pole of strength m kept at a distance of d from the centre of a short magnet of magnetic moment M on its equatorial line is
  66. If three identical bar magnets each of magnetic moment ‘M’ are arranged in the form of an equilateral triangle such that unlike poles are in contact. The resultant magnetic moment is
  67. The magnetic induction and the intensity of magnetic field inside an iron core of an electromagnet are 1 Wbm –2 and 150 Am –1 respectively. The relative permeability of iron is : μ 0 = 4 π x 10 – 7 Henry / m
  68. Two short magnets each of moment M are placed one over the other at right angles. The resultant magnetic induction at a point ‘P’, that lies at a distance ‘d’ from the common centre is
  69. Two identical isolated poles are separated by a distance of 3mm along a vertical line are at equilibrium. If the mass of each pole 50gr-wt Then pole strength of each is
  70. The magnetic needle of a vibration magnetometer makes 12 oscillations per minute in the horizontal component of earth’s magnetic field. When an external short bar magnet is placed at some distance along the axis of the needle in the same line it makes 15 oscillations per minute. If the poles of the bar magnet are inter changed, the number of oscillations it makes per minute is
  71. In an uniform field the magnetic needle completes 10 oscillations in 92 seconds. When a small magnet is placed in the magnetic meridian 10 cm due north of needle with north pole towards south completes 15 oscillations in 69 seconds. The magnetic moment of magnet (B H = 0.3 G) is
  72. A magnet makes 12 oscillation per minute at a place where horizontal component of earth’s field is 6.4 × 10 –3 T. It is found to require 8 seconds per oscillation at another place X. The vertical component of earth’s field at X, where resultant field makes angle 60 0 with horizontal is —×10 –4 T
  73. An iron rod is subjected to cycles of magnetisation at the rate of 50Hz. Given the density of the rod is 8 × 10 3 kg/m 3 and specific heat is 0.11 × 10 –3 cal/ kg 0 C. The rise in temperature per minute, if the area enclosed by the B – H loop corresponds to energy of 10 –2 J is (Assume there is no radiation losses)
  74. A short magnet oscillates in vibration magnetometer with a frequency 10 Hz where horizontal component of earth’s magnetic field is 12 μ T. A downward current of 15 A is established in the vertical wire placed 20 cm west of the magnet. New frequency is
  75. A magnet of magnetic moment 50 i ^ Am 2 is placed along the x-axis in a magnetic field B = 0 . 5 i ^ + 3 . 0 j ^ T . The torque acting on the magnet is
  76. A very long magnet of pole strength 16 A-m is placed vertically with its one pole on the table. At what distance from the pole, there will be a neutral point on the table. (B H = 4 × 10 –5 Wbm –2 )
  77. Two isolated north poles of pole strengths 16 A-m and 4 A-m are at 30 cm apart in air. The distance of neutral point from the weaker pole is
  78. A Dip circle lying initially in the magnetic meridian, the angle of dip is 45 o . Now dip circle is rotated through 30 o in the horizontal plane. The apparent angle of dip is
  79. A rod of ferromegnetic material with dimensions 10cm × 0.5cm × 2cm is placed in a magnetising field of intensity 2 ×10 5 A/m. The magnetic moment produced due it is 6 amp–m 2 . The value of magnetic induction will be —– 10 –2 T.
  80. Two small magnets have their masses and lengths in the ratio 1:2. The maximum torques experienced by them in a uniform magnetic field are the same. For small oscillations, the ratio of their time periods is (Ignore width of magnet)
  81. Find the false statement.
  82. Which of the following is not a consequence of Gauss’s law?
  83. If ϕ 1 and ϕ 2 be the angles of dip observed in two vertical planes at right angles to each other and ϕ be the true angle of dip, then
  84. T o is time period of oscillation of the needle in uniform horizontal magnetic field (B H ) of the earth. If another magnetic field is applied perpendicular to B H such that the needle deflects by θ for its equilibrium. Now period of oscillation of the needle is T. The relation between T and T o is :
  85. Which of the following is the definition for magnetic meridian of Earth?
  86. At a place the value of H and V are 0.4 × 10 –4 T and 0.3 × 10 –4 T respectively. The resultant earth’s magnetic field is
  87. Needles N 1 , N 2 and N 3 are made of ferromagnetic, a para-magnetic and a diamagnetic substance respectively. A magnet when brought close to them will
  88. A magnetic needle oscillates in horizontal plane with a period T at a place where the angle of dip is 60 o . When the same needle is made to oscillate in a vertical plane coinciding with the magnetic meridian, its period will be
  89. At the magnetic poles of the earth, a compass needle will be
  90. Soft iron is used to manufacture electromagnets because their
  91. A magnet of dipole moment 2 Am 2 is deflected through 30 o from magnetic meridian. The required deflecting torque is (B H = 0.4 x 10 -4 T)
  92. When a bar magnet is placed at 90 o to a uniform magnetic field, it is acted upon by a couple which is maximum. For the couple to be half of the value, the magnet should be inclined to the magnetic field at an angle of
  93. A steel wire of length I has a magnetic moment M. It is bent in l-shape as shown in fig (2). The new magnetic moment is
  94. For substances hysteresis (B-H) curves are given in fig. (5). For making temporary magnet which would be the best
  95. A copper rod is suspended in a non-homogeneous magnetic field region. The rod when in equilibrium will align itself
  96. The correct I-H curve for paramagnetic material is represented by
  97. The property of retentivity of material is useful in the construction of
  98. Domain formation is the necessary feature of
  99. A magnetic needle, suspended horizontally by an unspun silk fibre, oscillates in the horizontal plane, because of a restoring force originating mainly from
  100. The area enclosed by a hysteresis loop is a measure of
  101. A current loop placed in a magnetic field behaves like a
  102. A dip circle is so set that it moves freely in the magnetic meridian. In this position, the angle of dip is 40 o . Now the dip circle is rotated so that the plane in which the needle moves makes an angle of 30 o with the magnetic meridian. In this position, the needle will dip by the angle
  103. A bar magnet of magnetic moment M is kept in a uniform magnetic field of strength B, making angle θ with its direction. The torque acting on it is
  104. A magnet of magnetic moment M is rotated through 360 o in a magnetic field H, the work done will be
  105. In hydrogen atom the electron is making 6.6 x 10 15 rev/sec. around the nucleus in an orbit of radius o .528 A o . The magnetic moment (Am 2 ) will be
  106. If the area of I-H hysteresis loop and B-H hysteresis loop are denoted by A 1 and A 2 respectively, then
  107. The given figure (3) represents a material which is
  108. A neutral point in the magnetic field is a point where
  109. The materials suitable for making electromagnetic should have
  110. The work done in turning a magnet of magnetic moment M by angle of 90 o from the meridian, is n times the corresponding work done to turn in through an angle of 60 o . The value of n is given by
  111. A bar magnet of length 10 cm and having the pole strength equal to 10 -3 Wb is kept in a magnetic field having magnetic induction equal to 4 π x 10 -3 T. It makes an angle 30 o with the direction of magnetic induction. The value of the torque acting on the magnet is μ 0 = 4 π × 10 − 7 WbA − 1 m
  112. The time period of a freely suspended magnet is 4 sec. If it is broken in length into two equal parts and one part is suspended in the same way, then its time period in seconds will be
  113. The time period of oscillation of a magnet in vibration magnetometer is 1.5 second. The time period of oscillation of another magnet similar in size, shape and mass but having one-fourth magnetic moment than that of the first magnet oscillating at the same place will be
  114. A magnet when placed perpendicular to a uniform field of strength 10 -4 W/m 2 experiences a couple of moment 4 x 10 -5 N/m. The magnetic moment is
  115. The angle of dip is the angle
  116. The B-H curve (a) and (b) in fig are associated with
  117. The permanent magnet is made from which one of the following substances ?
  118. The work done in deflecting a magnet of magnetic moment ‘M through al angle ‘ θ ‘ in a field of strength ‘H’ is
  119. The variation of magnetic susceptibility ( χ ) with temperature for a diamagnetic substance is best represented by Fig
  120. A bar magnet when placed at an angle of 30 o to the direction of magnetic field induction of 5 x 10 -4 T, experiences a moment of couple 25 x 10 -6 Nm. If the length of the magnet is 5 cm, its pole strength is
  121. When a paramagnetic substance is placed in a magnetic field, the magnetic induction inside the substance
  122. A bar magnet is held perpendicular to a uniform field. If the couple acting on the magnet is to be halved by rotating it, the angle by which it is to be rotated is
  123. At a certain place, horizontal component of earth’s magnetic field is 3 times the vertical component. The angle of dip at the plane is
  124. The temperature at and above which a ferromagnetic material becomes paramagnetic is called
  125. Magnets A and B are geometrically similar but the magnetic moment of A is twice that of B. If T 1 and T 2 be the time periods of the oscillation when their poles and unlike poles are kept together respectively, then T 1 T 2 will be
  126. A magnetised wire of magnetic moment M and length I is bent in the form of a semi-cycle of radius r. The new magnetic moment is
  127. If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferro-magnetic material are denoted by μ d , μ p and μ f respectively, then
  128. Two magnets of moment m and 2m are tied at an angle of 60 o to each other. The magnetic moment of the combination will be
  129. Which of the following statements is incorrect about hysteresis ?
  130. The length of magnet is large compared to its width and breadth. The time period of its oscillation in a vibration magnetometer is 2 s. The magnet is cut along its length into three equal parts and three parts are then placed on each other with their like poles together. The time period of this combination will be
  131. The magnetic field at a point ‘P’ on the axial line of a short bar magnet is 5 μT ,due South. Now the magnet is turned through 90 0 in anti clockwise direction. Then, the magnetic field at the same point ‘P’ would be
  132. Two poles separated by 10 cm experiences a force of 5 mN. Find the force between them when the distance is doubled and the pole strengths are doubled
  133. The restoring torque for a magnet oscillating in the vibration magnetometer is provided by
  134. Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic dipole moment m . Which configuration has highest net magnetic dipole moment?
  135. If the length of a bar magnet increases, then A) magnetic induction on the axial line decreases B) magnetic induction on the equatorial line increases
  136. The magnetic susceptibility is negative for
  137. The time period of a magnet ( when behaving like a compound pendulum) is T. The bar magnet is cut into 4 equal parts by cutting it normal to its length. The time period of each of them in the same field is
  138. At a point A on the earth’s surface the angle of dip, δ = + 25 ° . At a point B on the earth’s surface the angle of dip, δ = – 25 ° . We can interpret that
  139. A magnet oscillating in a horizontal plane has a time period of 2 sec at a place where the angle of dip is 30 o and 3 second at another place where the angle of dip is 60 o . The ratio of resultant magnetic fields at these two places is
  140. The susceptibility of diamagnetic material
  141. A bar magnet of length ‘ l ‘ and magnetic dipole moment ‘M’ is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be
  142. A magnet of magnetic moment ‘M’ is rotated through 2 π radians in a magnetic field of induction B. The work done is
  143. A bar magnet of magnetic moment M is placed at right angles to a magnetic induction B. If a force F is experienced by each pole of the magnet, the length of the magnet will be
  144. A short bar magnet of magnetic moment 20 A m 2 has cross sectional area of 1 . 5 × 10 – 4 m 2 . If the intensity of magnetization of the magnet is 10 5 A/m. The length of magnet is
  145. If θ 1 and 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
  146. Two blocks A and B of masses 3 m and m respectively are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in figure. The magnitudes of acceleration of A and B immediately after the string is cut, are respectively
  147. An iron rod of susceptibility 599 is subjected to a magnetising field of 1200 A m – 1 . The permeability of the material of the rod is μ 0 = 4 π × 10 − 7 T   m   A − 1
  148. Isogonic lines on a magnetic map will have
  149. Soft iron is used as core in transformer because. It has
  150. The force between two poles is reduced to ‘x’ newtons when their original separation is increased ‘n’ times, it is increased to ‘y’ newtons when their separation is made 1 n th of their original value. The relation between ‘x’ and ‘y’ is
  151. A magnet of length 0.1 m and pole strength 50 Am is kept in a magnetic field 4 × 10 – 5 T at an angle 30 0 to it. The couple acting on it is
  152. The relations amongst the three elements of earth’s magnetic field, namely horizontal component H, vertical component V and dip δ are, ( B E = total magnetic field)
  153. Two reasons for using soft iron as the material for electromagnets…..
  154. Select the correct option:
  155. Dimensional formula for pole strength of a magnet is
  156. When a magnet is suspended at an angle of 30 0 with magnetic meridian, it makes an angle of 45 0 with horizontal. The true dip at that place is
  157. A magnet of length L and Moment M is cut into two halves perpendicular to its axis. One piece A is bent into a semicircle of radius R and is joined to the other piece at the poles as shown. The moment of the resulting magnet is,
  158. The pole strength of a bar magnet is 48 Am and the distance between its poles is 25cm. The moment of the couple by which it can be placed at an angle of 30 0 with the uniform magnetic field of flux density 0.15 N/Am will be.
  159. A magnet of magnetic moment 50 i ^ A m 2 is placed along the X-axis in a magnetic field B   =   ( 0.5 i ^   +   3.0 j ^ ) T . The torque acting on the magnet is
  160. A bar magnet of length 3cm has points A and B along its axis at distance of 24cm and 48cm on the opposite sides. Ratio of magnetic fields at these points will be
  161. The horizontal components of earth’s magnetic field at a place is 0 . 3 × 10 – 4 T. If the angle of dip is 60 0 , what is the total earth’s magnetic field?
  162. Two magnets A and B are identical and these are arranged as shown in the figure. The (short magnets are considered) ratio of distance d 1 and d 2 will be,
  163. The horizontal component of the earth’s magnetic field is 0.22G and total magnetic field is 0.4G. The angle of dip is
  164. A bar magnet has a Coercivity 4 × 10 3 A m – 1 . It is desired to demagnetize it by inserting it inside a solenoid 12cm long and having 50 turns. The current that should be sent through the solenoid is
  165. The susceptibility of a ferromagnetic material is K at 27 0 C . At what temperature will its susceptibility be K/2,
  166. Time period of oscillations with a standard rectangular bar magnet the time period of a vibration magnetometer is 4 seconds. The bar magnet is cut parallel to its length into four equal pieces. The time period is, when one piece is used (in seconds) …………
  167. Force between two identical bar magnets whose centre are ‘r ’ meter apart is 6.4 N. When their axis are in the same line. If the separation is increased to ‘2r ’ meter, the force between them is reduced to
  168. A bar magnet has a magnetic moment of 100 Am 2 . The magnet is suspended in a magnetic field of 0.60 NA -1 m -1 . The torque required to rotate the magnet from its equilibrium position through an angle of 30 0 will be:
  169. The ratio of magnetic moments of two short magnets which gives null deflection in tan B position at 6 cm and 9 cm from the center of a deflection magnetometer is
  170. A solenoid has core of a material with relative permeability 501 , its winding carry a current of 1 A and the number of turns of solenoid is 500 per meter. The magnetization of the material is
  171. At a temp of 27 0 C the susceptibility of a ferromagnetic material is found to be χ . Its susceptibility at 327 0 C is
  172. Two identical magnetic dipoles of magnetic moments 1 . 0 A – m 2 each, placed at a separation of 2m with their axes perpendicular to each other, The resultant magnetic field at a point mid-way between the dipoles is
  173. A paramagnetic substance of susceptibility 2 × 10 − 4 is placed in a magnetic intensity of 4×10 -4 A-m -1 . Then the intensity of magnetization in the unit of A-m -1 is
  174. The values of saturation magnetization, retentivity and coercivity respectively from the following graph (between H and B) are
  175. At a temp of 300 K, the susceptibility of a ferromagnetic material is found to be χ . Its susceptibility at 450 K is χ 1 . Then χ 1 χ =
  176. The magnitude of magnetic field due to a dipole of magnetic moment 1.2 Am 2 at a point 1 m away from it in a direction making an angle of 60 0 with the dipole axis is
  177. The magnetic scalar potential due to a magnetic field at a point on its axis situated at a distance of 20 cm from its center is found to be 1.2 × 10 − 5  V . Then, the magnetic moment of the dipole is
  178. The susceptibility of magnesium at 300 K is 1.8 × 10 − 5 . At what temperature will be the susceptibility decreases to 1.2 × 10 − 5
  179. A bar magnet has a length of 8 cm. The magnet field at a point at a distance 3 cm from the center in the broadside on position (equatorial) is formed to be 4 × 10 − 6 T . Find the pole strength of the magnet.
  180. The magnetic moment of the assumed dipole at the earth’s center is 8 × 10 22   A m 2 . The magnetic field B at the geomagnetic poles of the earth is P × 10 15 R 3 .(where R is Radius of earth). Then the value of ‘P’ is
  181. Two short bar magnets of magnetic moments ‘M’ each are arranged at the opposite corners of a square of side ‘d’ such that their corners coincide with the corners and their axes are parallel. If the like pole are in the same direction, the magnetic field at any of the other corners of the square is
  182. A compass needle placed at a distance ‘r’ from a short magnet in tan A position shows a deflection of 60 0 , if the distance is increased to r ( 3 ) 1 / 3 . Then the deflection of the compass needle is
  183. A dip needle vibrates in the vertical plane perpendicular to the magnetic meridian. The time period of vibration is found to be 2 second. The same needle is then allowed to vibrate in the horizontal plane and time period is again found to be 2 second. Then, the angle of dip is
  184. At a temperature of 333 0 C , the susceptibility of a ferromagnetic material is found to be ‘ χ ‘ . Its susceptibility at 30 0 C is
  185. Two long bar magnets are placed with their axes coinciding in such away that the north pole of the first magnet is 1.0 cm from the south pole of the second. If both the magnets have a pole strength of 40 Am. The force exerted by one magnet on the other is N
  186. A bar magnet of magnetic moment ‘M’ is bent in the form of an arc which makes angle 60 0 . The percentage change in magnetic moment is
  187. A bar magnet of length 0.1m has a pole strength of 50Am. The magnetic field at a distance of 0.2m from its centre on its equatorial line
  188. Two identical magnetic dipoles of magnetic moments 1 A m 2 each placed at separation of 2m with their axis perpendicular to each other. The resultant magnetic field at a point midway between the dipoles is
  189. Two short magnets each moment 10 Am 2 are placed in end- on position so that their centres are 0.1m apart. The force between them is
  190. At a place the values of B H and B V are 0 . 4 × 10 – 4 T and 0 . 3 × 10 – 4 T respectively, then the angle of dip is
  191. A magnetic needle is free to rotate in a vertical plane, which makes an angle of 60 0 with the magnetic meridian. If the needle stays in a direction making an angle of tan – 1 2 3 with the horizontal , what would be the dip at that place?
  192. A short bar magnet of magnetic moment 1 . 28 × 10 – 2 Am 2 is arranged in the magnetic meridian with its south pole pointing geographic north. If B H = 0 . 4 G , the distance between the two null points is
  193. Two short bar magnets of magnetic moments 0 . 125 Am 2 and 0 . 512 Am 2 are placed with their like poles facing each other. If the distance between the centres of the magnet is 0.26m , the distance of neutral point from the weaker bar magnet is ————–
  194. The force between the two poles is reduced to ‘ x ‘ newton, when their separation is increased to n times. From this value, it increases by ‘y’ newtons when their separation made 1 n t h of their original value. The relation between x and y is
  195. What is the magnetic field induction at the centre of line joining the two poles of a horse shoe magnet of poles strength ‘m’ and separated by a distance ‘a’ is
  196. A pivoted magnetic needle of length 2 l and pole strength ‘ m ‘ is at rest in magnetic meridian. It is held in equilibrium at an angle θ to a magnetic induction field B H by applying a force F at a distance ‘ r ‘ from the pivot along a direction perpendicular to the field, then F=?
  197. A short bar magnet produces magnetic fields of equal induction at two points; one on the axial line and the other on the equatorial line. What is the ratio of their distances?
  198. When a bar magnet is placed at 90 0 to a uniform magnetic field. It is acted upon by a couples which is maximum. For the couple to be half of the maximum value at what angle should the magnet be inclined to the magnetic field B
  199. A magnetic dipole is under the influence of two magnetic fields the angle between the two field directions is 60 0 and one of the fields has a magnitude of 1 . 2 X 10 – 2 T . If the dipole comes to stable equilibrium at an angle of 15 ° with this field, what is the magnitude of the other field?
  200. The work done in turning a bar magnet normal to field direction from the direction of the field is 40 × 10 – 6 J . The kinetic energy attained by it when it reaches the field direction when released is —————
  201. Two small magnets each of magnetic moment 10 Am 2 are placed in axial position 0.1m part from their centres. What is the force acting between them?
  202. A bar magnet of magnetic moment M 1 is suspended by a wire in a magnetic field. The upper end of the wire is rotated through 180 0 , then the magnet rotated through 45 0 .under similar conditions another magnet of magnetic moment M 2 is rotated through 30 0 . Then find the ratio of M 1 and M 2
  203. A magnetic needle of pole strength 20 3 Am is pivoted at its centre. Its North pole is pulled eastward by a string. The horizontal force required to produce a deflection of 30 0 from magnetic meridian (take B H = 10 − 4 T )
  204. A bar magnet of moment of inertia I is vibrated in a magnetic field of induction 0 . 4 × 10 – 4 T . The time period of vibration is 12sec. The magnetic moment of the magnet is 120 Am 2 . The moment of Inertia of the magnet is ( in K g m 2 )
  205. Two small magnets have their masses and lengths in the ratio 1:2 . The maximum torques experienced by them in a uniform magnetic field are the same. For small oscillations, the ratio of their time periods is
  206. A cylindrical bar magnet ( radius = 1 cm , length = 10 cm ) has field intensity of 1000 A/m . The magnetic moment in the bar if permeability of its material is 6.3 × 10 − 4 H / m is ———-
  207. The magnetic scalar potential due to a magnetic dipole at a point on its axis situated at a distance of 20cm from its center is found to be 1.2 × 10 − 5 T m . The magnetic moment of the dipole is
  208. The plane of the dip circle is set in the geo-graphical meridian and the apparent dip is θ 1 . It is then set in a vertical plane perpendicular to the geo graphical meridian the apparent dip becomes θ 2 .The angle of declination α at that place is given by
  209. A magnet suspended so as to swing horizontally makes 50 vibrations per minutes at a place where dip is 30 ∘ , and 40 vibrations where dip is 45 ∘ . Compare the earth’s total fields at the two places.
  210. A Short bar magnet is placed in the magnetic meridian of the earth with north pole pointing north. Neutral points are found at a distance of 30cm from the magnet an the east west line drawn through the middle point of the magnet. The magnetic moment of the magnet in A m 2 is B H = 3 . 6 × 10 – 5 T
  211. Two short magnets of magnetic moments 0.8 A m 2 and 2.7 A m 2 are placed along the same straight line with their like poles towards each other. The distance between their centers is 40cm. The distance of the neutral point on their common axial line from the center of the stronger magnet is
  212. Example for artificial Magnets are
  213. When a thin bar magnet of Magnetic moment is bent into an arc of a circle subtending at an angle ‘ θ ’ radians at the centre of the circle. Then its new magnetic moment is given by
  214. What is the direction of Magnetic field induction? a) on the axial line b) on the equatorial line
  215. The Relation between force between the two poles in free space and medium
  216. The magnetic susceptibility is negative for
  217. The net magnetic flux through any closed surface is zero. Which of the following law encapsulates this statement.
  218. Curie temperature is the temperature above which
  219. What is the formula for the magnetic field induction at any general point ‘p’
  220. Curve between Magnetic moment and temperature of magnet is
  221. Susceptibility is small and positive for
  222. The substance best suited for preparing the core of an electro magnets is
  223. If the magnetic moment of the atoms of a substance is zero, the substance is called
  224. The area of B-H hysteresis loop is an indication of the
  225. The magnetic field due to a small dipole of a given magnetic dipole moment varies as inverse of the
  226. The time period of a freely suspended magnet does not depend upon
  227. A bar magnet of magnetic moment ‘M’ is freely suspended in a uniform magnetic field of strength ‘B’. The work done in rotating the magnet through angle θ is
  228. A magnetic dipole is free to rotate in a uniform magnetic field. For what orientation of the magnet with respect to the magnetic field. a) Torque is maximum b) Potential energy is maximum
  229. The dipole moment of a coil of area ‘A’ and no. of turns N and carrying current (i) will be
  230. What is the expression for the minimum potential energy of magnet
  231. If earth is considered as a short magnet with its centre coinciding with the centre of earth. Then the angle of dip ? at a place where the magnetic latitude ‘ λ ’ given by
  232. A magnet is placed with its north pole towards geomagnetic north pole. In it’s map of magnetic field the null points will be
  233. Which of the following statements is incorrect about Hysteresis?
  234. The basic magnification curve for a ferromagnetic material is shown is figure. Then the value of relative permeability is highest for the point
  235. Angle of Dip is 90 0 at
  236. What is the magnetic field induction (of earth) when a bar magnet is placed with its axial line perpendicular to magnetic meridian with North pole facing towards east to achieve neutral point?
  237. The magnetic susceptibility of a rod is 499. The absolute permeability of the material of the rod is p π × 10 – 5 H / m . Find p
  238. A magnetized needle of magnetic moments 4.8 × 10 − 2 A m 2 is placed at 30 0 with the direction of a uniform magnetic field of 3 × 10 − 2 T . If the needle is pivoted through its center of mass and is free to rotate in the plane of the magnetic field. Find the angular frequency (in rad/s) for small oscillations. The moment of inertia of the needle about the axis of rotation is 2 . 25 × 10 – 5 k gm 2
  239. The susceptibility of a magnesium at 300 K is 1.2 × 10 − 5 . The temperature (in K) at which the susceptibility increases to 1.8 × 10 − 5 is —————
  240. The coercivity of a small magnet where the Ferro magnet gets demagnetised is 3 × 10 3 A / m . The current to be passed in a solenoid of length 10cm and no. of turns 100, so that the magnet gets demagnetized when inside the solenoid is
  241. Paramagnetic sample shows a net magnetisation of 4A/m , when placed in an external magnetic field of 0.3T at a temperature of 8K. When the same sample is placed in an external magnetic field of 0.4T at a temperature of 4K, the magnetisation will be p 3 ( A / m ) . Find p
  242. The percentage increase in the magnetic field B when the space within a current carrying toroid is filled with aluminium, with a susceptibility of 2 . 1 × 10 – 5 , is 2 . 1 × 10 – p . Find p .
  243. A short bar magnet of magnetic moment 30 Am 2 has a cross sectional area of 1 . 5 × 10 – 4 m 2 . If the intensity of magnetisation of the magnet is 10 5 A / m , the length ( in m ) of the magnet is
  244. A paramagnetic sample shown a net magnetisation of 8 A/m. When placed in an external magnetic field of 0.6T at a temperature of 4K. When placed in an external magnetic field of 0.3T at a 16K , then find magnetisation ( in A/m) at this temperature
  245. A bar magnet has coercivity of 4 × 10 3 A / m . It is desired to demagnetize it by inserting it inside a solenoid 12cm long having 60 turns. What current ( in A ) should be sent through the solenoid ?
  246. The magnetic susceptibility of a medium is 0.83 . Its relative permeability is
  247. The material suitable for making electromagnets should have
  248. The magnetic length of a bar magnet is 10cm then its geometric length is
  249. Two similar bar magnets ‘P’ and ‘Q’ each of magnetic moment ‘M’, are taken. If P is cut along its axis line and Q is cut along its equatorial line, all the four pieces obtained have,
  250. The force experienced by a magnetic pole of strength ‘m’ kept at a distance of ‘d’ from the center of a short magnet of magnetic moment ‘M’ on its equatorial line is
  251. The ratio of magnetic inductions on the axial line of a bar magnet at distances 10cm and 15cm from the center of the magnet are in the ratio 5.8: 1. The distance between the two poles of the magnet is
  252. Three identical bar magnets, each of magnetic moment M, are placed in the form of an equilateral triangle with north pole of one touching the south pole of the other. The net magnetic moment of the system is
  253. At a place, if the earth’s horizontal and vertical components of magnetic fields are equal, then the angle of dip will be
  254. Two short magnets of magnetic moments 0.8 A m 2 and 2.7 A m 2 are placed along the same straight line with their like poles towards each other. The distance between their centers is 40cm. The distance of the neutral point on their common axial line from the center of the stronger magnet is
  255. The dipole moment of each molecule of a paramagnetic gas is 1 . 5 × 10 – 23 A m 2 . The temperature of gas is 27 0 C and the number of molecules per unit volume in it is 2 × 10 26 m – 3 . The maximum possible intensity of magnetization in the gas will be
  256. Two ferromagnetic materials X and Y have hysteresis curves of the shapes as shown in figure. Which of the following option is correct
  257. In an uniform field the magnetic needle completes 10 oscillations in 92 seconds. When a small magnet is placed in the magnetic meridian 10cm due north of needle with north pole towards south completes 15 oscillations in 69 seconds. The magnetic moment of magnet is ………… A – m 2 (given B H = 0 . 3 G )
  258. A bar magnet of 10cm long is kept with its N-pole pointing north. A neutral point is formed at a distance of 15cm from each pole. Given the horizontal component of earth’s field is 0.4G, the pole strength of the magnet is……. A-m
  259. A bar magnet having a magnetic moment of 4×10 4  JT -1 is free to rotate in a horizontal plane. A horizontal magnetic field B=3 × 10 − 4   T exits in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction 60 0 from the field is
  260. If a magnet is suspended at an angle of 30 0 to the magnetic meridian, the dip needle makes an angle of 60 0 with the horizontal. The real dip is
  261. The magnetic susceptibility of material of a rod is 599, permeability of vacuum is 4 π × 10 − 7   h e n r y / m . The absolute permeability of material of rod in herny/m is
  262. The ratio of saturation magnetization to retentivity calculated from the figure is
  263. A magnet is 10 cm long and its pole strength is 120 CGS units(1 CGS unit of pole strength=0.1 Am). Find the magnitude of magnetic field ‘B’ at a point on its axis at a distance 20 cm from it.
  264. A bar magnet made of steel has a magnetic moment of 5   A m 2 and a mass of 40 gm. If the density of steel is 8 × 10 3   k g / m 3 . The intensity of magnetization of the magnet is × 10 4   A / m
  265. The figure gives experimentally measured B vs H variation in ferromagnetic material. The ratio of saturation magnetization to retentivity is
  266. Force between two identical bar magnets whose centers are ‘ r’ meter apart is 4.8 N When their axis are in the same line. If the separation is increased to ‘2r’ meter, then the force between them reduced and becomes ‘P’ . Then P is N.
  267. The susceptibility of a material at 300 K is 1.2 × 10 − 5 , If the temperature is 327 0 C , then its susceptibility is × 10 − 5 .
  268. Force between two identical bar magnets whose centers are ‘ r’ meter apart is 4.8 N When their axis are in the same line. If the separation is increased to ‘2r’ meter, then the force between them reduced and becomes ‘P’ . Then P is N.
  269. A thin bar magnet of length 2L is bent at the midpoint so that the angle between them is 60 0 . The new length of the magnet is
  270. A short bar magnet of length 1 cm has points A & 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:
  271. A magnet of magnetic moment ‘M’ is cut into two equal parts. The two parts are placed perpendicular to each other, so that their north poles touch each other. The resultant magnetic moment is
  272. A bar magnet having a magnetic moment of 2×10 4  JT -1 is free to rotate in a horizontal plane. A horizontal magnetic field B=4 × 10 − 4  T exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction 60 0 from the field is
  273. A bar magnet has a magnetic moment of 200 Am 2 . The magnet is suspended in a magnetic field of 0.50 NA − 1 m − 1 . The torque required to rotate the magnet from its equilibrium position through an angle of 30 0 will be
  274. A short bar magnet of magnetic moment 0.2 JT − 1 is placed in a uniform magnetic field of 0.16 T . The magnet is in stable equilibrium when the potential energy is
  275. A uniform magnetic needle is suspended from its center by a thread. Its upper end is now loaded with a mass of 50 mg when the needle becomes horizontal. If the strength of each pole is 98.1 ab-amp.cm & g is 981 cm/s 2 , then the vertical component of the earth’s magnetic field is
  276. Two bar magnets of the same mass, same length and breadth but having magnetic moments M and 2M are joined together pole to pole and suspended by a string. The time period of assembly in a magnetic field of strength H is 3 seconds. If now the polarity of one of the magnets is reversed and the combination is again made to oscillate in the same field, the time of oscillation is
  277. The vertical component of earth’s magnetic field is zero at (or) the earth’s magnetic field always has a vertical component except at the
  278. Property possessed by ferromagnetic substance only
  279. The figure gives experimentally measured B vs. H variation in a ferromagnetic material. The retentivity, co-ercivity and saturation, respectively, of the material are.
  280. Torque required to deflect a bar magnet in a uniform magnetic field through an angle of 30 0 is 25 N – m. Then the work done by an external agent to deflect the magnet through an additional angle of 30 0 will be
  281. The strength of the magnetic field in which the magnet of a vibration magnetometer is oscillating is increased 4 times its original value. The frequency of oscillation would then become
  282. A bar magnet having magnetic dipole moment M is cut along its length into two equal parts. One of these parts is placed over the other at the centre at right angles. Then resultant dipole moment of the combination is
  283. The vector sum of magnetic dipole moments due to orbital and spin motion of electrons in a dia magnetic atom is
  284. A bar magnet is suspended by a string in a uniform magnetic field making an angle of 60 o with the field. Torque required to hold the magnet in that position is 25 × 10 − 3   N − m . Then the work done by an external agent to rotate the magnet clockwise through an angle of 90 o is (Take 3 = 1.7 )
  285. The relative permeability is represented by μ r and the susceptibility is denoted by χ for a magnetic substance. Then for a paramagnetic substance
  286. A wire carrying current I is bent in the shape ABCDEFA as shown, where rectangle ABCDA and ADEFA are perpendicular to each other. If the sides of the rectangles are of lengths a and b, then the magnitude and direction of magnetic moment of the loop ABCDEFA is:
  287. A perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a paramagnetic substance. The whole system is placed in a uniform magnetic field B . Then the field inside the paramagnetic substance is :
  288. A small bar magnet placed with its axis at 30 ° with an external field of 0.06 T experiences a torque of 0.018    N m . The minimum work required to rotate it from its stable to unstable equilibrium position is :
  289. A paramagnetic sample shows a net magnetization of 6 A/m when it is placed in an external magnetic field of 0.4 T at a temperature of 4 K. When the sample is placed in an external magnetic field of 0.3 T at a temperature of 24 K, then the magnetization will be:
  290. A circular coil has moment of inertia 0.8 k g   m 2 around any diameter and is carrying current to produce a magnetic moment of 20 A m 2 . The coil is kept initially in a vertical position and it can rotate freely around a horizontal diameter. When a uniform magnetic field of 4 T is applied along the vertical, it starts rotating around its horizontal diameter. The angular speed the coil acquires after rotating by 60 ° will be:
  291. A square loop of side 2a , and carrying current i, is kept in XZ plane with its center at origin . A long wire carrying the same current i is placed parallel to the z-axis and passing through the point (0, b, 0) , (b > > a ) the magnitude of the torque on the loop about Z-axis is given by :
  292. Relative permeability of a magnetic material is 651 when a cylindrical rod made of this material is placed in a magnetising field of 8 × 10 − 5   T − m − A − 1 , find dipole moment per unit volume of the rod in T − m − A − 1 .
  293. Which of the following statements is incorrect
  294. Two short magnetic dipoles N 1 = M i ^  and  N 2 ⇀ = M j ^ are placed at the origin. Then magnetic induction at the point r , 0 is
  295. A dip needle lies initially in the magnetic meridian when it shows an angle of dip θ at a place. When the dip circle is rotated through an angle 30 o in the horizontal plane, the dip needle shows an angle of dip θ 1 . Then the value of tan θ 1 tan θ is
  296. The area of hysteresis loop of a material is equivalent to 250 Joule. When 10kg of a material, of density 7.5 gm/cm 3 , is magnetized by an alternating field of 50Hz, then the energy lost in one hour will be:
  297. A thin bar magnet is bent in the form of a semicircle and its magnetic moment is M. If it is straightened and given a shape of an arc which subtends an angle 120 0 at the center then its new magnetic moment will be
  298. Two bar magnets of different lengths produce magnetic field induction of same magnitude at points on the axial line, at the same distance in each case. Then
  299. Magnetic field applied to a ferromagnetic material is slowly increased. The magnetic domains within it
  300. Three magnets of same length but moments M, 2M and 3M are arranged in the form of an equilateral triangle with opposite poles nearer, the resultant magnetic moment of the arrangement is
  301. 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
  302. A bar magnet of length 10 cm and pole strength 20 A-m is deflected through 30 o from the magnetic meridian. If earth’s horizontal component field is 320 4 π A / m . The moment of the deflecting couple is
  303. A bar magnet suspended in a field of induction 1.5 × 10 –6 T has a time period π 5 sec The moment of inertia about the axis of suspension is 1.5×10 –4 kgm 2 . The magnetic moment of the magnet is
  304. In Fig. the magnetic needle has magnetic moment 6.7×10 –2 Am 2 and moment of inertia I = 7.5×10 –6 kg m 2 . It performs 10 complete oscillations in 6.70 s. What is the magnitude of the magnetic field ?
  305. A long bar magnet of time period T is cut into four equal parts by cutting it perpendicular to both length and breadth. The time period of each part is
  306. A bar magnet suspended freely in uniform magnetic field is vibrating with a time period of 3 seconds. If the field strength is increased to four times of the earlier field strength, the time period will be (in seconds)
  307. If the angles of dip at two places are 30 o and 45 o respectively, then the ratio of horizontal components of Earth’s magnetic field at the two places will be
  308. The true value of dip at a place is 45 o . If the vertical plane carrying the needle is turned through 60 o from the magnetic meridian, the apparent dip is
  309. A short bar magnet with its north pole facing north forms a neutral point at P in a horizontal plane. If the magnet is rotated by 90 o in the horizontal plane, the net magnetic induction at P is (Horizontal component of earth’s magnetic field = B H )
  310. A paramagnetic sample shows a net magnetization of 0.8 A/m, when placed in an external magnetic field of strength 0.8 T at a temperature 5 K. When the same sample is placed in an external magnetic field of 0.4 T at a temperature of 20 K, the magnetization is
  311. A short bar magnet placed with its axis at 30 o with a uniform external magnetic field of 0.16 T experiences a torque of magnitude 0.032 Nm. If the bar magnet were free to rotate, its P.E when it is in stable and unstable equilibrium are respectively.
  312. A dip needle vibrates in the vertical plane perpendicular to the magnetic meridian. The time period of vibration is found to be 2 seconds. The same needle is then allowed to vibrate in the horizontal plane and the time period is again found to be 2 seconds. Then the angle of dip is
  313. The plane of the dip circle is set in the geographical meridian and the apparent dip is θ 1 . It is then set in a vertical plane perpendicular to the geographical meridian, the apparent dip becomes θ 2 . The angle of declination α at that place is given by
  314. The total magnetic flux in a material, which produces a pole of strength m p when a magnetic material of cross-sectional area A is placed in a magnetic field of strength H, will be
  315. The number of atoms per unit volume in a sample of iron is 9 × 10 28 atoms /m 3 . The magnetic moment of every iron atom is 1.5×10 –23 Am 2 . If all dipoles are aligned in a domain due to ferromagnetic interaction, then magnetic moment and the pole strength of the rod of length 10 cm and area of cross – section 1cm 2 is
  316. A bar magnet of 10 cm long is kept with its N – pole pointing north. A neutral point is formed at a distance of 15 cm from each pole. Given the horizontal component of earth’s field is 0.4 Gauss, the pole strength of the magnet is
  317. If a bar magnet of pole strength ‘m’ and magnetic moment ‘M’ is cut equally 5 parts parallel to its axis and 4 parts perpendicular to its axis then the pole strength and magnetic moment of each piece are respectively
  318. A magnetized wire of moment ‘M’ is bent into an arc of a circle subtending an angle 60 o at the center. The new magnetic moment will be
  319. The resultant magnetic moment for the following arrangement is (the vectors are non coplanar)
  320. If at any place, the angle of dip is θ and magnetic latitude is λ , then
  321. A bar magnet when placed at an angle of 30 0 to the direction of magnetic field induction of 5×10 –5 T, experiences a moment of couple 2.5 × 10 –6 N–m. If the length of the magnet is 5 cm its pole strength is
  322. A short magnet of moment 6.4 A-m 2 lies in the magnetic meridian with north pole facing south (B H = 1.6 gauss). The distance between the two neutral points is
  323. A bar magnet has a coercivity 4 × 10 3 Am –1 . It is desired to demagnetize it by inserting it inside a solenoid 12 cm long and having 60 turns. The current that should be sent through the solenoid is
  324. A solenoid has a core of material with relative permeability 400. The windings of solenoid are insulated from the core and carry a current of 2 A. If no. of turns per unit length is 1000, the magnetising current
  325. A bar magnet takes π /10 seconds to complete one oscillation in uniform magnetic field. The moment of inertia of the magnet about the axis of rotation is 1.2 × 10 –4 kgm 2 and the earth’s horizontal magnetic field is 30 μ T. The magnetic moment of the magnet is………..Am 2
  326. A magnet is suspended in the magnetic meridian with an untwisted wire. The upper end of the wire is rotated through 180 o to deflect the magnet by 30 o from magnetic meridian. Now this magnet is replaced by another magnet. Now the upper end of the wire is rotated through 270 o to deflect the magnet 30 o from the magnetic meridian. The ratio of the magnetic moments of the two magnets is
  327. Find the correct combination regarding relative permeability and magnetic susceptibility of a paramagnetic substance.
  328. A dip needle lies initially in the magnetic meridian when it shows an angle of dip θ at a place. The dip circle is rotated through an angle x in the horizontal plane and then it shows an angle of dip θ 1 . Then tanθ 1 tanθ is
  329. Which one of the following, when suspended freely, slowly sets itself parallel to the direction of the magnetic field?
  330. Magnets A and B are geometrically similar but the magnetic moment of A is twice that of B. If T 1 and T 2 be the time periods of the oscillation when their like poles and unlike poles are kept together respectively, then T 1 /T 2 will be
  331. Electromagnets are made of soft iron because soft iron has
  332. Hysteresis loop represent energy loss per cycle. Then energy loss is:
  333. At a place on the surface of earth, the dip circle shows reading of 30 0 and in a plane perpendicular to the initial it gives reading of 45 0 . What is the reading of dip circle at that place in magnetic meridian?
  334. Which among the following is not attracted by magnets?
  335. Arrange the following in the increasing order of magnetic susceptibility.
  336. Pick out the temperature at which iron becomes paramagnetic?
  337. If the angles of dip at two places are 30 and 45° respectively, then the ratio of horizontal components of earth’s magnetic field at the two places assuming magnitude of total magnetic field of earth is same will be
  338. An isolated magnetic pole
  339. A dip needle in a plane perpendicular to magnetic meridian will remain
  340. Declination is the angle between
  341. Curie temperature is the temperature above which
  342. A steel wire of length l has a magnetic moment M It is then bent into a semicircular arc. The new magnetic moment is
  343. A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through 60 o . The torque needed to maintain the needle in this position will be
  344. The magnetic moment of a magnet is 0.1 Am 2 and force acting on each pole in a uniform magnetic field of strength 0.36 oersted is 1.224 x 10 -4 N. The distance between the poles of the magnet is
  345. The workdone in deflecting a small magnet of magnetic moment 10 Am 2 through 180 o from uniform magnetic field of strength 0.4 x 10 -4 T is
  346. A magnet of magnetic moment M is lying in a magnetic field of inclination B. W 1 is the work done in turning it from 0 o to 60 o and W 2 is the work done in turning it from 30 o to 90 o . Then
  347. A bar magnet of magnetic moment 2.0 J/T lies aligned with the direction of uniform magnetic field of 0.25 T. What is the amount of work required to turn the magnet so as to align its magnetic moment normal to the field direction ?
  348. If a magnet is suspended at an angle of 30 o to the magnetic meridian, the dip needle makes an angle of 45 o with the horizontal. The real dip is
  349. A thin rectangular magnet suspended freely has a period of oscillation equal to T Now, it is broken into equal halves (each having half of original length) and one piece is made to oscillate freely in the same field. If its period of oscillation is T’, then the ratio T’/T is
  350. At a certain place a magnet makes 30 oscillations per minute. At another place where the magnetic field is doubled its time period will be
  351. Points A and B are situated along the extended axis of a 2 cm long bar magnet at a distance x and 2 x cm respectively from the pole nearer to the points. The ratio of the magnetic field at A and B will be
  352. The magnetic field at a distance d from a short bar magnet in longitudinal and transverse position are in the ratio
  353. The period of oscillation of a magnet in a vibration magnetometer is 2 sec. The period of oscillation of magnet whose magnetic moment is four times that of the first magnet is
  354. The ratio of magnetic fields due to a small bar magnet in the end-on position to broad-side-on position is
  355. A magnetising field of 2 x 10 3 amp/m produces a magnetic flux density of 8 π tesla in an iron rod. The relative permeability of the rod will be
  356. Two bar magnets of the same mass, same length and breadth but having magnetic moments M and 2M are joined together pole to pole and suspended by a string. The time period of assembly in a magnetic field of strength H is 3 second. If now the polarity of one of the magnets is reversed and the combination is again made to oscillate in the same field, the time of oscillation is
  357. A dip needle lies initially in the magnetic meridian when it shows an angle of dip θ at a place. The dip circle is rotated through an angle x in the horizontal plane and then it shows an angle of dip θ ‘. Then tan θ ‘ / tan θ is
  358. Two magnets A and B are identical and these are arranged as shown in fig.(3) 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 al angle θ under the influence of magnets. The ratio of distances d 1 and d 2 will be
  359. A magnet is suspended horizontally in the earth’s magnetic field. When it is displaced and then released, it oscillates in the horizontal plane with a period T If a piece of wood of the same moment of inertia (about the axis of rotation) as the magnet is attached to magnet, what would be the new period of oscillation of the system become ?
  360. 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 30 o and 15 oscillations per min. at a place where dip angle is 60 o . The ratio of the total earth’s magnetic field at the two Places is
  361. A bar magnet A of magnetic moment M A is found to oscillate at a frequency twice that of an identical magnet B of magnetic moment M B when placed in a vibrating magnetometer. We may say that
  362. The ratio of time periods of oscillation of two magnets of same moment of inertia suspended in a magnetic field is 1 : 2. The ratio of their magnetic moments is
  363. In a vibration magnetometer, the time period of a bar magnet oscillating in horizontal component of earth’s magnetic field is 2 sec. When the magnet is brought near a field magnet F and parallel to it, the time period reduces to 1 sec. The ratio of F/H of the horizontal component H and the field F due to magnet will be
  364. Which of the following is most suitable for the core of electromagnets
  365. The graph between λ and, 1/T for paramagnetic material will be represented by
  366. Soft iron is used in many parts of electrical machines for
  367. Curie’s law is obeyed well by
  368. Susceptibility is positive for
  369. The mass of a specimen of a ferromagnetic material is 0.6 kg and the density is 7.8 x 10 3 kg /m 3 . If the area of hysteresis loop of alternating magnetising field of frequency 50 Hz is 0.722 MKS units, then hysteresis loss per second will be
  370. A magnetic needle suspended by a silk-thread is vibrating in the earth’s magnetic field. If the temperature of the needle is increased 1000 o C, then
  371. Lines of force, due to earth’s horizontal magnetic field, are
  372. The magnetic field of earth is due to
  373. The magnetic field strengths at a distance d from a short bar magnet in longitudinal and transverse positions are in the ratio
  374. The period of oscillations of a magnetic needle in a magnetic field is 1.0 s If the length of the needle is halved by cutting it then the time period will be
  375. Two magnets A and B of the same dimensions and mass are made to oscillate in the same magnetic field. A performs 15 vibrations per minute and B, 10 vibrations per minute. The magnetic moments of the two magnets are in the ratio of
  376. The vertical component of the earth’s magnetic field is zero at a place where the angle of dip is
  377. Two magnets each of magnetic moment ‘M’ are placed so as to form a cross at right angles to each other. Magnetic moment of the system will be
  378. A magnet 10 cm long and having a pole strength of 2 amp-m is deflected through 30 o from the magnetic meridian. The horizontal component of earth’s induction is 0.32 x 10 -4 T. The value of deflecting couple is
  379. The value of horizontal component of earth’s magnetic field at a place is 0.35 x 10 -4 T. If the angle of dip is 60 o , the value of vertical component of earth’s magnetic field is about
  380. The magnetic moment of a short magnet is 8 amp-m 2 . What is the magnetic induction at a point 20 cm away on its equatorial line from its mid-point ?
  381. A magnetic needle vibrates in the vertical plane perpendicular to the magnetic meridian. Its time period is 2 seconds. If the same needle vibrates in the horizontal plane and the time period is again 2 seconds, what is the angle of dip at that place
  382. A magnet makes 40 oscillations per minute at a place having magnetic field intensity H = 0.1 x 10 -5 T. At another place, it takes 2.5 sec to complete one vibration. The value of earth’s horizontal field at that place
  383. The moment of a short magnet is 4 amp-m 2 . The magnetic induction at a point on the axial line at a point 40 cm away from its mid-point is
  384. The use of study of hysteresis curve for a given material is to estimate the
  385. The relative permeability is represented by μ r and the susceptibility by λ for a magnetic substance. Then for a paramagnetic substance
  386. Two short bar magnets of magnetic moments M each are arranged at the opposite corners of a square of side d such that their centres coincide with the corners and their axes are parallel. If the like poles are in the same direction, the magnetic induction at any of the other corners of the square is
  387. A vibration magnetometer consists of two identical bar magnets placed one over the other such that they are perpendicular and bisect each other. The time period of oscillation in a horizontal magnetic field is 2 5/4 second. One of the magnets is removed and if the other magnet oscillates in the same field, then the time period in second is
  388. The magnetic susceptibility of a material of a rod is 499. Permeability of vacuum is 4 π x 10 -7 Wm. Absolute permeability of the material of the rod in henry/metre is
  389. A coil in the shape of an equivalent triangle of side l is suspended between the pole pieces of a permanent magnet such that B is in plane of coil. If due to a current i in the triangle a torque τ acts on it, the side l of the triangle is
Chat on WhatsApp Call Infinity Learn

    Register to Get Free Mock Test and Study Material



    +91

    Verify OTP Code (required)

    I agree to the terms and conditions and privacy policy.