All STD 12 - Magnetism and matter questions
Newest firstShowing 51–69 of 69 questions
- 51. A magnetic compass needle oscillates \(30\) times per minute at a place where the dip is \(45^o\), and \(40\) times per minute where the dip is \(30^o\). If \(B_1\) and \(B_2\) are respectively the total magnetic field due to the earth at the two places, then the ratio \(B_1/B_2\) is best given by 2019 Medium
- 52. A paramagnetic material has \(10^{28}\,atoms/m^3.\) Its magnetic susceptibility at temperature \(350\,K\) is \(2.8 \times 10^{-4}.\) Its susceptibility at \(300\,K\) is 2019 Medium
- 53. A paramagnetic substance in the form of a cube with sides \(1\, cm\) has a magnetic dipole moment of \(20 \times 10^{-6}\, J/T\) when a magnetic intensity of \(60 \times 10^3\, A/m\) is applied. Its magnetic susceptibility is 2019 Medium
- 54. At some location on earth the horizontal component of earth’s magnetic field is \(18\times10^{-6}\,T\). At this location, magnetic needle of length \(0.12\, m\) and pole strength \(1.8\, A\,m\) is suspended from its mid-point using a thread, it makes \(45^o\) angle with horizontal in equilibrium. To keep this needle horizontal, the vertical force that should be applied at one of its ends is 2019 Medium
- 55. Two magnetic dipoles \(X\) and \(Y\) are placed at a separation \(d\), with their axes perpendicular to each other. The dipole moment of \(Y\) is twice that of \(X\). A particle of charge \(q\) is passing through their mid-point \(P\), at angle \(\theta = 45^o\) with the horizontal line as shown in the figure. What would be the magnitude of force on the particle at that instant ? (\(d\) is much larger than the dimensions of the dipole)
2019 Hard - 56. The \(B-H\) curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solenoid with \(1000\, turns/cm\) . The current that should be passed in the solenoid to demagnetise the ferromagnet completely is
2018 Medium - 57. A magnetic dipole in a constant magnetic field has 2017 Medium
- 58. A magnetic needle of magnetic moment \(6.7 \times 10^{-2} \) \(Am^2\) and moment of inertia \(7.5 \times 10^{-6}\) \( kgm^2\) is performing simple harmonic oscillations in a magnetic field of \(0.01\ T\). Time taken for \(10\) complete oscillations is.....\(s\) 2017 Medium
- 59. A fighter plane of length \(20\, m\), wing span (distance from tip of one wing to the tip of the other wing) of \(15\,m\) and height \(5\,m\) is lying towards east over Delhi. Its speed is \(240\, ms^{-1}\) . The earth's magnetic field over Delhi is \(5 \times 10^{-5}\,T\) with the declination angle \( \sim {0^o}\) and dip of \(\theta\) such that \(\sin \,\theta = \frac{2}{3}\). If the voltage developed is \(V_B\) between the lower and upper side of the plane and \(V_W\) between the tips of the wings then \(V_B\) and \(V_W\) are close to 2016 Hard
- 60. Hysteresis loops for two magnetic materials \(A\) and \(B\) are given below These materials are used to make magnets for elecric generators, transformer core and electromagnet core. Then it is proper to use
2016 Easy - 61. A \(25\,cm\) long solenoid has radius \(2\,cm\) and \(500\) total number of turns. It carries a current of \(15\,A.\) If it is equivalent to a magnet of the same size and magnetization \(\vec M\) ( magnetic moment/ volume), then \(\left| {\vec M} \right|\) is 2015 Medium
- 62. 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 \(30\, cm\) from the magnet on the East - West line, drawn through the middle point of the magnet. The magnetic moment of the magnet in \(Am^2\) is close to: (Given \(\frac{{{\mu _0}}}{{4\pi }}\, = 10^{- 7}\) in \(SI\,units\) and \(B_H\, =\) Horizontal component field \(= 3.6\times10^{-5}\, tesla\)) 2015 Medium
- 63. An example of a perfect diamagnet is a superconductor. This implies that when a superconductor is put in a magnetic field of intensity \(B\), the magnetic field \(B_s\) inside the superconductor will be such that 2014 Medium
- 64. The coercivity of a small magnet where the ferromagnet gets demagnetized is \(3 \times 10^3\) \( Am^{-1}\) The current required to be passed in a solenoid oflength \(10\ cm\) and number of turns \(100\), so that the magnet gets demagnetized when inside the solenoid, is 2014 Medium
- 65. The magnetic field of earth at the equator is approximately \(4 \times 10^{-5}\, T\) . The radius of earth is \(6.4 \times 10^6\, m\). Then the dipole moment of the earth will be nearly of the order of 2014 Medium
- 66. The mid points of two small magnetic dipoles of length \(d\) in end-on positions, are separated by a distance \(x, (x > > d)\). The force between them is proportional to \(x^{-n}\) where \(n\) is
2014 Hard - 67. Three identical bars \(A, B\) and \(C\) are made of different magnetic materials. When kept in a uniform magnetic field, the field lines around them look as follows: Make the correspondence of these bars with their material being diamagnetic \((D)\), ferromagnetic \((F)\) and paramagnetic \((P)\)
2014 Medium - 68. The earth's magnetic field lines resemble that of a dipole at the centre of the earth. If the magnetic moment of this dipole is close to \(8 \times 10^{22}\, Am^2\), the value of earth 's magnetic field near the equator is close to....\(Gauss\) (radius of the earth \(= 6.4 \times 10^6\, m\)) 2013 Medium
- 69. Two short bar magnets oflength \(1\ cm\) 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 \(20.0\ cm\). The value of the resultand horizontal magnetic induction at the mid-point \(O\) of the line joining their centres is close to (Horizontal component of earth.s magnetic induction is \(3.6 \times 10^{-5}\) \(Wbm^{-2}\) ) 2013 Hard
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