Electromagnetic Induction PYQs Set 3 (PDF)

Set 3 of 11 · Questions 61-90 of 319

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Mere Teacher · Previous Year Questions JEE Main Physics · Electromagnetic Induction · Set 3 (Q61-90)
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61. $A metal ring is held horizontally and bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet is$ (1) $more than g$ (2) $equal to g$ (3) $less than g$ (4) $either (a) or (c)$ 62. $Direction of current induced in a wire moving in a magnetic field is found using$ (1) $Fleming's left hand rule$ (2) $Fleming's right hand rule$ (3) $Ampere's rule$ (4) $Right hand clasp rule.$ 63. $A condenser of capacity C is charged to a potential difference of V_{1} . The plates of the condenser are then connected to an ideal inductor of inductance L. The current through the inductor when the potential difference across the condenser reduces to V_{2} is$ (1) $(\frac{C ( V _{1} - V _{2} ) ^{2}}{L})^{\frac{1}{2}}$ (2) $\frac{C ( V _{1}^{2} - V _{2}^{2} )}{L}$ (3) $\frac{C ( V _{1}^{2} + V _{2}^{2} )}{L}$ (4) $(\frac{C ( V _{1}^{2} - V _{2}^{2} )}{L})^{\frac{1}{2}}$ 64. $A coil of resistance 400Ω is placed in a magnetic field. If the magnetic flux φ (wb) linked with the coil varies with time t (sec) as φ = 50 t^{2} + 4. The current in the coil at t = 2 sec is:$ (1) $0.5A$ (2) $0.1 A$ (3) $2 A$ (4) $1 A$ 65. $A long solenoid with 40 turns per em carries a current of 1 A . The magnetic energy stored per unit volume is J / m^{3} .$ (1) $3.2 π$ (2) $32 π$ (3) $1.6 π$ (4) $6.4 π$ 66. $In an electrical circuit R, L, C and ac voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and the current in the circuit is π /3 . If instead, C is removed from the circuit, the phase difference is again π /3 . The power factor of the circuit is$ (1) $\frac{1}{2}$ (2) $\frac{1}{2}$ (3) $1$ (4) $\frac{3}{2}$ 67. $The primary of a transformer when connected to a dc battery of 10 volt draws a current of 1 mA . The number of turns ofthe primary and secondary windings are50 and 100 respectively. The voltage in thesecondary and the current drawn by the circuit in the secondary are respectively$ (1) $20V and 2.0 mA$ (2) $10 V and 0.5mA$ (3) $Zero volt and therefore no current$ (4) $20 V and 0.5 mA$ 68. $A conducting wire of length 2500 m is kept in east-west direction, at a height of 10 m from the ground. If it falls freely on the ground then the current induced in the wire is (Resistance of wire = 252 Ω, acceleration due to gravity g = 10 m / s^{2}, B_{H} = 2 \times 10^{- 5} T)$ (1) $0.2 A$ (2) $0.02 A$ (3) $0.01 A$ (4) $2 A$ 69. $A big circular coil of 1000 turns and average radius 10 m is rotating about its horizontal diameter at 2 rad s^{- 1} . If the vertical component of earth's magnetic field at that place is 2 \times 10^{- 5} T and electrical resistance of the coil is 12.56Ω, then the maximum induced current in the coil will be [NEET 2022]$ (1) $0.25 A$ (2) $1.5 A$ (3) $1 A$ (4) $2 A$ 70. $A magnetic field of 2 \times 1 0^{- 2} T acts at right angles to a coil of area 100 c m^{2}, with 50 turns. The average e.m.f. induced in the coil is 0. 1 V, when it is removed from the field in t sec. The value of t is$ (1) $10 s$ (2) $0.1 s$ (3) $0.01 s$ (4) $1 s$ 71. $The magnetic flux near the axis and inside the air core solenoid of length 60 cm carrying current I is 1.57 \times 10^{- 6} Wb . Its magnetic moment will be (cross-sectional area of a solenoid is very small as compared to its length, μ_{0} = 4 π \times 10^{- 7} SI unit)$ (1) $0.25 A$ (2) $0.50 A$ (3) $0.75 A$ (4) $1 A$ 72. $An inductor 20 mH, a capacitor 50 μF and a resistor 40 Ω are connected in series across a source of emf V = 10 sin 340 t . The power loss in A.C. circuit is$ (1) $0.76 W$ (2) $0.89 W$ (3) $0.51 W$ (4) $0.67 W$ 73. $The total charge, induced in a conducting loop when it is moved in magnetic field depends on$ (1) $the rate of change of magnetic flux$ (2) $initial magnetic flux only$ (3) $the total change in magnetic flux$ (4) $final magnetic flux only$ 74. $The expression for the magnetic energy stored in a solenoid of length L, in terms of magnetic field B and area A is$ (1) $\frac{1}{2 μ _{0}} B^{2} AL$ (2) $\frac{1}{2 ϵ _{0}} B^{2} AL$ (3) $\frac{1}{2 μ _{0}} BA^{2} L$ (4) $\frac{1}{2 ϵ _{0}} B A^{2} L$ 75. $A long solenoid of radius R carries a time (t) - dependent current I (t) = I_{0} t (1 - t) . A ring of radius 2 R is placed coaxially near its middle. During the time interval 0 \leq t \leq 1, the induced current (I_{R}) and the induced EMF (V_{R}) in the ring change as:$ (1) $Direction of I_{R} remains unchanged and V_{R} is zero at t=0.25$ (2) $At t=0.5 direction of I_{R} reverses and V_{R} is zero$ (3) $At t=0.25 direction of I_{R} reverses and V_{R} is maximum$ (4) $Direction of I_{R} remains unchanged and V_{R} is maximum at t=0.5$ 76. $A magnetic field of 2 \times 10^{- 2} T acts right angles to a coil of area 100 cm^{2} with 50 turns. The average e.m.f. induced in the coil is 0.1 V, when it is removed from the field in time ' t' The value of ' t' is$ (1) $2 \times 10^{- 3} s$ (2) $0.5 s$ (3) $0.1 s$ (4) $1 s$ 77. $Two coils have a mutual inductance 0.005 H. The current changes in the first coil according to equation I = I_{0} sinωt, where I_{0} = 10 A and ω = 100 π rad / sec . The maximum value of e.m.f. in the second coil is$ (1) $π$ (2) $5 π$ (3) $2 π$ (4) $4 π$ 78. $A long solenoid has 20 turns per cm . A small loop of area \frac{4}{π} cm^{2} is placed inside the solenoid normal to its axis. If the current carried by the solenoid changes steadily from 1.0 A to 3.0 A in 0.2 s, what is the magnitude of the induced emf in the loop while the current is changing?$ (1) $2.4 μV$ (2) $3.2 μV$ (3) $7.2 μV$ (4) $4.8 μV$ 79. $The source of time varying magnetic field may be (A) a permanent magnet (B) an electric field changing linearly with time (C) direct current (D) a decelerating charge particle (E) an antenna fed with a digital signal Choose the correct answer from the options given below.$ (1) $(C) and (E) only$ (2) $(D) only$ (3) $(A) only$ (4) $(B) and (D) only$ 80. $What is the self‐inductance of a coil which produces 5 V when the current changes from 3 ampere to 2 ampere in one millisecond?$ (1) $5000 henry$ (2) $5 milli‐henry$ (3) $50 henry$ (4) $5 henry$ 81. $A wheel with 20 metallic spokes each 1 m long is rotated with a speed of 120 rpm in a plane perpendicular to a magnetic field of 0.4 G. The induced emf between the axle and rim of the wheel will be (1 G = 10^{- 4} T) [NEET 2020]$ (1) $2.51 \times 10^{- 4} V$ (2) $2.51 \times 10^{- 5} V$ (3) $4.0 \times 10^{- 5} V$ (4) $2.51 V$ 82. $A 800 turn coil of effective area 0.05 m^{2} is kept perpendicular to a magnetic field 5 \times 1 0^{- 5} T . When the plane of the coil is rotated by 9 0^{o} around any of its coplanar axis in 0.1 s, the self-induced in the coil will be$ (1) $0.02 V$ (2) $2 V$ (3) $0.2 V$ (4) $2 \times 1 0^{- 3} V$ 83. $Consider a circular coil of wire carrying constant current I, forming a magnetic dipole. The magnetic flux through an infinite plane that contains the circular coil and excluding the circular coil area is given by φ_{i} . The magnetic flux through the area of the circular coil area is given by φ_{0} . Which of the following option is correct?$ (1) $φ_{i} > φ_{0}$ (2) $φ_{i} < φ_{0}$ (3) $φ_{i} = - φ_{0}$ (4) $φ_{i} = φ_{0}$ 84. $The magnetic flux through a coil perpendicular to its plane is varying according to the relation φ = 5 t^{3} + 4 t^{2} + 2 t - 5 Weber. If the resistant of the coil is 5 ohm, then the induced current through the coil at t = 2 sec will be:$ (1) $15.6 A$ (2) $16.6 A$ (3) $17.6 A$ (4) $18.6 A$ 85. $If current ' T' is flowing in the closed circuit with collective resistance ' R', the rate of production of heat energy in the loop as we pull it along with a constant speed ' V' is (L = length of conductor; B = magnetic field)$ (1) $\frac{BLV}{R}$ (2) $\frac{B ^{2} L ^{2} V ^{2}}{R ^{2}}$ (3) $\frac{BLV}{R ^{2}}$ (4) $\frac{B ^{2} L ^{2} V ^{2}}{R}$ 86. $The magnetic potential energy stored in a certain inductor is 25 mJ, when the current in the inductor is 60 mA. This inductor is of inductance [NEET 2018]$ (1) $1.389 H$ (2) $138.88 H$ (3) $0.138 H$ (4) $13.89 H$ 87. $A conducting circular loop is placed in X - Y plane in presence of magnetic field B = (3 t^{3} j + 3 t^{2} k) in SI unit. If the radius of the loop is 1m, the induced emf in the loop, at time, t = 2s is nπV . The value of n is........$ 88. $A 10 Ω, 20 mH coil carrying constant current is connected to a battery of 20 V through a switch is opened current becomes zero in 100 μ s. The average emf induced in the coil is............V.$ 89. $A circular coil of 1000 turns each with area 1 m^{2} is rotated about its vertical diameter at the rate of one revolution per second in a uniform horizontal magnetic field of 0.07T. The maximum voltage generation will be_______V.$ 90. $The current in an inductor is given by I = (3 t + 8) where t is in second. The magnitude of induced emf produced in the inductor is 12 mV . The self-inductance of the inductor________mH .$