Moving Charges & Magnetism PYQs Set 3 (PDF)

Set 3 of 19 · Questions 61-90 of 549

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Mere Teacher · Previous Year Questions JEE Main Physics · Moving Charges & Magnetism · Set 3 (Q61-90)
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61. $If the magnetic field in a plane electromagnetic wave is given by B \to= 3 \times 10^{- 8} sin (1.6 \times 10^{3} x + 48 \times 10^{10} t) j^T then what will be expression for electric field?$ (1) $E \to= 3 \times 10^{- 8} sin (1.6 \times 10^{3} x + 48 \times 10^{10} t) j^V / m$ (2) $E \to= 3 \times 10^{- 8} sin (1.6 \times 10^{3} x + 48 \times 10^{10} t) i^V / m$ (3) $E \to= 60 sin (1.6 \times 10^{3} x + 48 \times 10^{10} t) k^V / m$ (4) $E \to= 9 sin (1.6 \times 10^{3} x + 48 \times 10^{10} t) k^V / m$ 62. $A charge ' q' moves with a velocity 2 ms^{- 1} along x -axis in a uniform magnetic field B = (2 i + 2 j + 3 k) T, then charge will experience a force$ (1) $In y - z plane$ (2) $Along - y axis$ (3) $Along + z axis$ (4) $Along - z axis$ 63. $A long solenoid is formed by winding 70 turns c m^{- 1} . If 2.0 A current flows, then the magnetic field produced inside the solenoid is _____________(μ_{0} = 4 π x 1 0^{- 7} T m A^{- 1})$ (1) $1232 x 1 0^{- 4} T$ (2) $176 x 1 0^{- 4} T$ (3) $352 x 1 0^{- 4} T$ (4) $88 x 1 0^{- 4} T$ 64. $A horizontal metal wire is carrying an electric current from the north to the south. Using a uniform magnetic field, it is to be prevented from falling under gravity. The direction of this magnetic field should be towards the$ (1) $north$ (2) $south$ (3) $east$ (4) $west$ 65. $Magnetic field intensity at the center of the coil of 50 turns, radius 0. 5 m and carrying a current of 2 A, is$ (1) $3 \times 1 0^{- 5} T$ (2) $1.25 \times 1 0^{- 4} T$ (3) $0.5 \times 1 0^{- 5} T$ (4) $4 \times 1 0^{6} T$ 66. $A particle of mass m, charge Q and kinetic energy T enters in a transverse uniform magnetic field of induction B . After 3 seconds the kinetic energy of the particle will be$ (1) $T$ (2) $4 T$ (3) $3 T$ (4) $2T.$ 67. $A charged particle moves through a magnetic field in a direction perpendicular to it. Then the$ (1) $speed of the particle remains unchanged$ (2) $direction of the particle remains unchanged$ (3) $acceleration remains unchanged$ (4) $velocity remains unchanged.$ 68. $A charged particle is moving in a uniform magnetic field penetrates a layer of lead and thereby loses half of its kinetic energy, then the radius of curvature of its path is$ (1) $No change$ (2) $Reduced by \frac{1}{2} times of its initial values$ (3) $Reduced to \frac{1}{2} times of its initial values$ (4) $Reduce to \frac{1}{4} times of its initial values$ 69. $Two electrons, e_{1} and e_{2} of mass m and charge q are injected into the perpendicular direction of the magnetic field B such that the kinetic energy of e_{1} is double than that of e_{2} . The relation of their frequencies of rotation, f_{1} and f_{2} is$ (1) $f_{1} = f_{2}$ (2) $f_{1} = 2 f_{2}$ (3) $2 f_{1} = f_{2}$ (4) $4 f_{1} = f_{2}$ 70. $A circular coil of wire consisting of 100 turns each of radius 9 cm carries a current of 0.4 A . The magnitude of the magnetic field at the centre of coil is (μ_{0} = 12.56 \times 10^{- 7}) S.I. unit]$ (1) $2.4 \times 10^{- 11} T$ (2) $2.79 \times 10^{- 5} T$ (3) $2.79 \times 10^{- 4} T$ (4) $2.79 \times 10^{- 3} T$ 71. $A hoop and a solid cylinder of same mass and radius are made of a permanent magnetic material with their magnetic moment parallel to their respective axes. But the magnetic moment of hoop is twice of solid cylinder. They are placed in a uniform magnetic field in such a manner that their magnetic moments make a small angle with the field. If the oscillation periods of hoop and cylinder are T_{h} and T_{c} respectively, then:$ (1) $T_{h} = T_{c}$ (2) $T_{h} = 2 T_{c}$ (3) $T_{h} = 1.5 T_{c}$ (4) $T_{h} = 0.5 T_{c}$ 72. $The magnetic field due to current carrying a circular loop of radius 5 cm at a point on the axis at a distance of 12 cm from the centre is 250 μT . The magnetic field at the centre of the loop is$ (1) $2529 μT$ (2) $4394 μT$ (3) $1759 μT$ (4) $2908 μT$ 73. $An α -particle and a proton moving with the same kinetic energy enter a region of uniform magnetic field at right angles to the field. The ratio of the radii of the paths of α -particle to that of the proton is$ (1) $1 : 1$ (2) $1 : 2$ (3) $1 : 4$ (4) $1 : 8$ 74. $A moving coil galvanometer is converted into an ammeter of range 0 to 5 mA . The galvanometer resistance is 90Ω and the shunt resistance has a value of 10Ω . If there are 50 divisions in the galvanometer-turnedammeter on either sides of zero, its current sensitivity is$ (1) $2 \times 10^{4} div / A$ (2) $1 \times 10^{5} A / div$ (3) $2 \times 10^{4} A / div$ (4) $1 \times 10^{5} div / A$ 75. $A cylindrical conductor of radius R is carrying a constant current. The plot of the magnitude of the magnetic field, B with the distance, d from the center of the conductor, is correctly represented by the figure$ (1) (2) (3) (4) 76. $The number of turns in a coil of Galvanometer is tripled, then$ (1) $Both voltage and current sensitivity remains constant$ (2) $Voltage sensitivity increases 3 times and current sensitivity remains constant$ (3) $Both voltage and current sensitivity decrease by 33 %$ (4) $Voltage sensitivity remains constant and current sensitivity increases 3 times.$ 77. $A wire of length L meter carrying a current of I ampere is bent in the form of a circle. Its magnetic moment is [NEET 2020]$ (1) $(I L^{2} /4) Am^{2}$ (2) $(Iπ L^{2} /4) Am^{2}$ (3) $(2 I L^{2} / π) Am^{2}$ (4) $(I L^{2} /4 π) Am^{2}$ 78. $A deuteron of kinetic energy 50 keV is describing a circular orbit of radius 0.5 metre in a plane perpendicular to magnetic field B . The kinetic energy of the proton that describes a circular orbit of radius 0.5 metre in the same plane with the same B is$ (1) $25 keV$ (2) $50 keV$ (3) $200 keV$ (4) $100 keV$ 79. $A thin ring of radius R meter has charge q coulomb uniformly spread on it. The ring rotates about its axis with a constant frequency of f revolutions/s. The value of magnetic induction in Wb/ m^{2} at the center of the ring is$ (1) $\frac{μ _{0} qf}{2 πR}$ (2) $\frac{μ _{0} q}{2 πfR}$ (3) $\frac{μ _{0} q}{2 fR}$ (4) $\frac{μ _{0} qf}{2 R}$ 80. $A magnet of total magnetic moment 10^{- 2} i A - m^{2} is placed in a time varying magnetic field, B i (cos ωt) where B = 1 Tesla and ω = 0.125 rad / s The work done for reversing the direction of the magnetic moment at T = 1 second, is:$ (1) $0.02 J$ (2) $0.007 J$ (3) $0.028 J$ (4) $0.014 J$ 81. $Acceleration of a charged particle of charge ' q' and mass ' m' moving in a uniform electric field of strength ' E' is$ (1) $\frac{qE}{m}$ (2) $\frac{m}{qE}$ (3) $mqE$ (4) $\frac{q}{mE}$ 82. $Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency f Hz. The magnitude of magnetic induction at the centre of the ring is$ (1) $\frac{μ _{0} qf}{2 R}$ (2) $\frac{μ _{0} q}{2 fR}$ (3) $\frac{μ _{0} q}{2 πfR}$ (4) $\frac{μ _{0} qf}{2 πR}$ 83. $Torque acting on a rectangular coil carrying current I situated parallel to magnetic field of induction B having number of turns n and area A is$ (1) $nI (A \cdot B)$ (2) $\frac{nBA}{I}$ (3) $nI (A \times B)$ (4) $\frac{IBA}{n}$ 84. $A straight wire of mass 200 g and length 1.5 m carries a current of 2 A . It is suspended in mid-air by a uniform horizontal magnetic field B . The magnitude of B (in tesla) is (assume g = 9.9 m s^{- 2})$ (1) $2$ (2) $1.5$ (3) $0.55$ (4) $0.66$ 85. $Two parallel conductors carrying unequal currents in the same direction$ (1) $neither attract nor repel each other$ (2) $repel each other$ (3) $attract each other$ (4) $will have rotational motion.$ 86. $A square shaped coil of area 70 c m^{2} having 600 turns rotates in a magnetic field of 0.4 w b m^{- 2}, about an axis which is parallel to one of the side of the coil and perpendicular to the direction of field. If the coil completes 500 revolution in a minute, the instantaneous emf when the plane of the coil is inclined at 60° with the field, will be ____ V, (Take π = \frac{22}{7})$ 87. $A coil having 100 turns, area of 5 \times 10^{- 3} m^{2}, carrying current of 1 mA is placed in uniform magnetic field of 0.20 T such a way that plane of coil is perpendicular to the magnetic field. The work done in turning the coil through 90^{\circ} is_______μJ .$ 88. $A solenoid of length 0.5 m has a radius of 1 cm and is made up of ' m' number of turns. It carries a current of 5 A . If the magnitude of the magnetic field inside the solenoid is 6.28 \times 10^{- 3} T then the value of m is______$ 89. $The current of 5 A flows in a square loop of sides 1 m is placed in air. The magnetic field at the centre of the loop is X 2 \times 10^{- 7} T . The value of X is$ 90. $A long solenoid with 1000 turns/m has a core material with relative permeability 500 and volume . If the core material is replaced by another material having relative permeability of 750 with same volume maintaining same current of 0.75A in the solenoid, the fractional change in the magnetic moment of the core would be approximately . Find the value of ....x.$