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DEPARTMENT OF PHYSICS, , Physics, Time : 1.00 hr xil Marks : 20, , , , , , E.m. Induction And A.c. Current, 1) The inductance between A and D is :, , > IREQEG my GRINGO + DEGED A aH - 3H, , , , A) 3.66H B) 9H C) 0.66H D) 1H, , 2) Ina transformer, number of turns in the primary coil are 140 and that in the secondary coil are, 280. If current in primary coil is 4 A, then that In the secondary coil is :, , Aaa B)2A C)6A D)10A, , 3) When a current changes from + 2A to —2A in 0.05s, an emf of 8V induced In a coil. The, coefficient of self induction of coil is :, A)0.4H B) 0.8H C)0.1H D)0.2H, , 4) Inan oscillating circuit, the max. charge on capacitor is Q. The charge on capacitor when, energy is shared equally between the electric and magnetic field is :, , Q Q Q, A) = 8) = D, ) v3 ) v2 ea M3, , 5) The core of a transformer is laminated so as to :, , A) make it light weight B) make it robust and strong, C) increase the secondary voltage D) to reduce energy loss due to eddy, currents, , 6) Acoil having n turns and resistance R © is connected with a galvanometer of resistance 4R ©, . This combination is moved in t s from field W, to W> Weber. The induced current in circuit is, , n(We—W;) (Wo=W4) n(W2—W;), 5Rt 5Rnt Rt, , 7) A metal conductor of length 1 m rotates vertically about one of its ends with angular velocity, 5 rad s~' . If horizontal component of earth field is 0.2 x 10-*Am™ then emf induced is, , D) nRt, , A) B) c), , A) 50 mV B) 5 mv C)50uV D)5uV, , 8) Two concentric coils each of radius 2 x cm are placed at right angles to each other. Currents, of 3A and 4A are passing through them. The magnetic induction in Wb/m? at centre of coil is :, , A)5x105T B)7 x10-5T €)12x10T D) 10-5T

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9) Aconducting U-tude can slide inside another as shown in fig. maintaining electrical contacts, between them. The magnetic field is perpendicular to plane of paper of each tube move, , towards other with constant speed v then emf induced in each in terms of v Is :, ax X XX ax, , , , , , C5), , “OX xX —yxe*, A) Zero B) 2Blv C) Blv D) - Blv, , 10) An infinitely long cylinder is kept parallel to an uniform magnetic field B directed along, positive z-axis. The direction of induced current as seen from the z-axis will be :, , A) zero B) anti clockwise of the +ve z-axis, , C) clockwise of the +ve z-axis D) along the magnetic field., , 11) In an AC generator, a coil with N turns, all of the same area A and total resistance R, rotates, with frequency w in a magnetic field B. The maximum value of e.m.f generated in the coil is :, , A) N.A.B.R. w . B) NAB C) N.A.B.R. D) N.A.B. w ., , 12) A copper rod of length | is rotated about the end perpendicular to a uniform magnetic field B, with :, 1 1 Bw Bul, 2 Bw? poe Liss, A) Bul B) pbwl 55 ys, 13) A small square loop of wire of side | is placed inside a large square loop of side L. || >> 1)., The loops are coplanar and their centres coincide. The mutual induction of the system is :, l P L Lt, L B) L Cc) I D) i, 14) A power transformer is used to set up an alternating e.m.f. of 220 V to 4.4 kV to transmit 6.6, , kW of power. The primary coil has 1000 turns, what is current rating of secondary ? Assume, efficieny is 100%., , A), , A)25A B)15A C)1.0A D)O.75A, 15) Again in Q. 112, step up transformer at the plant is characterised by :, , A) 400 - 4000 V B) 440 - 7000 V C) 220 - 4000 V D) 220 - 7000 V, , 16) A thin ring of a radius 10 cm carries a uniformly distributed charge. The ring rotates at, constant speed of 1200 r.p.m. about its axis | to plane. Find the charge on ring if B =, 3.14 x 10°°T at centre., , A) 10-5 B)2x105¢ €)2.5 x10-5¢ D) 5.2 «10°C, , 17) A conducting ring of radius r is rolling without slipping with a constant angular velocity w. If, the magnetic field strength is B and is directed into the page then emf induced across PQ is :

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»Q, Bur? 7? Buwr?, 2 8, , 18) A small coil is introduced between the poles of an electromagnet so that its axis coincides, with the magnetic field direction. The number of turns is n and the cross sectional area of the, coil is A. When the coil turns through 180° about its diameter, the charge flowing through the, coil is Q. The total resistance of the circuit is R. What is the magnitude of the magnetic, induction ?, , , , , , A) Bur? B) C) 4Bwr? D), , 2QR Qn QR, , mA ©) SRA D) ana, , 19) A wire in the form of a circular loop of radius r lies with its plane normal to a magnetic field B., If the wire is pulled to take a square shape in the same plane in time t, the emf induced in the, loop Is given by :, , Br? ™ nBr ™ nBr? 7 mBr® ™, , ;@ io) 8) (1 3) o=-(1 3) (1 a), , 20) Two coaxial solenoids are made by winding thin insulated wire over a pipe of cross-sectional, area A = 10cm? and length = 20 cm. If one of the solenoids has 300 turns and the other 400, turns, their mutual inductance is ( ju) = 4 « 10°-’TmA~ ), , A) a B), , , , , , , , A), , A) 2.40 10*H B) 2.4n=10°H C) 4.8n x 10°*H D) 4.8an x 10-°H