Electromagnetic Induction PYQs Set 9 (PDF)

Set 9 of 10 · Questions 241-270 of 274

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Mere Teacher · Previous Year Questions NEET Physics · Electromagnetic Induction · Set 9 (Q241-270)
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241. $In the circuit shown below, the key K is closed at t = 0. The current through the battery is:$ (1) $\frac{V R _{1} R _{2}}{R _{1}^{2} + R _{2}^{2}} at t = 0 and \frac{V}{R _{2}} at t = ¥$ (2) $\frac{V}{R _{2}} at t = 0 and \frac{V ( R _{1} + R _{2} )}{R _{1} R _{2}} at t = ¥$ (3) $\frac{V}{R _{2}} at t = 0 and \frac{V R _{1} R _{2}}{R _{1}^{2} + R _{2}^{2}} at t = ¥$ (4) $\frac{V ( R _{1} + R _{2} )}{R _{1} R _{2}} at t = 0 and \frac{V}{R _{2}} at t = ¥$ 242. $Figure shows the circuit that contains three resistances (9Ω each) and two inductors (4 mH each). The reading of ammeter at the moment switch K is turned ON, is____A.$ (1) $2$ (2) $1$ (3) $zero$ (4) $3$ 243. $When the key K is pressed at time t = 0, then which of the following statement about the current I in the resistor AB ofthe given circuit is true?$ (1) $I oscillates between 1 mA and 2 mA$ (2) $at t = 0, I = 2 mA and with time it goes to 1 mA$ (3) $I = 1 mA at all t$ (4) $I = 2 mA at all t .$ 244. $A circular loop of radius 0.3 cm lies parallel to a much bigger circular loop of radius 20 cm. The center of the small loop is on the axis of the bigger loop. The distance between their centers is 15 cm. If a current of 2.0 A flows through the smaller loop, then the flux linked with bigger loop is:$ (1) $9.1 \times 1 0^{-11} weber$ (2) $6 \times 1 0^{-11} weber$ (3) $3.3 \times 1 0^{-11} weber$ (4) $6.6 \times 1 0^{-9} weber$ 245. $In an a . c . circuit the e.m.f. (ϵ) and the current (i) at any instant are given respectively by e = E_{0} sin ω t, i = I_{0} sin (ωt - φ) The average power in the circuit over one cycle of a . c . is$ (1) $\frac{E _{0} I _{0}}{2} cos ϕ$ (2) $E_{0} I_{0}$ (3) $\frac{E _{0} I _{0}}{2}$ (4) $\frac{E _{0} I _{0}}{2} sin ϕ$ 246. $Suppose a long solenoid of 100 cm length, radius 2 cm having 500 turns per unit length, carries a current I = 10 sin (ωt) A, where ω = 1000 rad . /s. A circular conducting loop (B) of radius 1 cm coaxially slided through the solenoid at a speed v = 1 cm / s . The r.m.s. current through the loop when the coil B is inserted 10 cm inside the solenoid is α / 2 μ A . The value of α is____. [Resistance of the loop = 10Ω]$ (1) $197$ (2) $80$ (3) $100$ (4) $280$ 247. $Eddy currents are produced when$ (1) $a metal is kept in varying magnetic field$ (2) $a metal is kept in steady magnetic field$ (3) $a circular coil is placed in a magnetic field$ (4) $through a circular coil, current is passed$ 248. $Given below are two statements: Statement I: The electric force changes the speed of the charged particle and hence changes its kinetic energy: whereas the magnetic force does not change the kinetic energy of the charged particle Statement II: The electric force accelerates the positively charged particle perpendicular to the direction of electric field. The magnetic force accelerates the moving charged particle along the direction of magnetic field. In the light of the above statements, choose the most appropriate answer from the options given below:$ (1) $Both Statement I and Statement II are correct.$ (2) $Both Statement I and Statement II are incorrect.$ (3) $Statement I is correct but Statement II is incorrect.$ (4) $Statement I is incorrect but Statement II is correct.$ 249. $The time constant of C‐R circuit is$ (1) $1/ CR$ (2) $C / R$ (3) $CR$ (4) $R / C$ 250. $The induced emf cannot be produced by$ (1) $moving a magnet near a circuit$ (2) $moving a circuit near a magnet$ (3) $changing the current in one circuit placed near the other$ (4) $maintaining large but constant current in a circuit$ 251. $A wheel with 10 spokes each of length L m is rotated with a uniform angular velocity (ω) in a plane normal to the magnetic field B . The emf induced between the axle and the rim of the wheel$ (1) $\frac{1}{2} N ω B L^{2}$ (2) $\frac{1}{2} ω B L^{2}$ (3) $ω b L^{2}$ (4) $N ω B L^{2}$ 252. $Figure shows a circuit that contains three identical resistors with resistance R = 9.0Ω each, two identical inductors with inductance L = 2.0 mH each, and an ideal battery with emf ϵ = 18 V ne current i through the batteryjust after the switch closed is$ (1) $0.2 A$ (2) $2 A$ (3) $4 A$ (4) $2 mA$ 253. $A metallic rod of length 'L' is rotated with an angular speed of ' ω' normal to a uniform magnetic field 'B' about an axis passing through one end of rod as shown in figure. The induced emf will be:$ (1) $\frac{1}{4} B^{2} Lω$ (2) $\frac{1}{4} B L^{2} ω$ (3) $\frac{1}{2} B L^{2} ω$ 254. $A rectangular loop of wire is placed in the XY -plane with its side of length 3 cm parallel to the X -axis and the side of length 4 cm parallel to the Y -axis. It is moving in the positive X -direction with the speed 10 cm / s . A magnetic field exists in the space with its direction parallel to the Z -axis. The field decreases by 2 \times 10^{- 3} T / cm along the positive X -axis and increases in time by 2 \times 10^{- 2} T / s . The induced emf in the wire is$ (1) $-4.8\times 1 0^{- 5} V$ (2) $4.8 \times 10^{- 5} V$ (3) $0$ (4) $3.6 \times 10^{- 5} V$ 255. $The magnitude of induced emf is directly proportional to the rate of change of magnetic flux linked with the coil. This statement is known as$ (1) $Ohm's law$ (2) $Lenz's law$ (3) $Faraday's law$ (4) $Ampere's law$ 256. $X PQY is a vertical smooth long loop having a total resistance R where PX is parallel to QY and separation between them is l . A constant magnetic field B perpendicular to the plane of the loop exists in the entire space. A rod CD of length L (L > l) and mass m is made to slide down from rest under the gravity as shown in figure. The terminal speed acquired by the rod is m / s . (g = acceleration due to gravity)$ (1) $\frac{8 mgR}{B ^{2} l ^{2}}$ (2) $\frac{2 mgR}{B ^{2} L ^{2}}$ (3) $\frac{mgR}{B ^{2} l ^{2}}$ (4) $\frac{2 mgR}{B ^{2} l ^{2}}$ 257. $A thin strip 10 cm long is on U shaped wire of negligible resistance and it is connected to a spring of spring constant 0.5 Nm^{- 1} (see figure). The assembly is kept in a uniform magnetic field of 0.1 T. If the strip is pulled from its equilibrium position and released, the number of oscillation it performs before its amplitude decreases by a factor of e is N. If the mass of the strip is 50 grams, its resistance 10Ω and air drag negligible, N will be close to$ (1) $1000$ (2) $50000$ (3) $5000$ (4) $10000$ 258. $In an A.C. circuit, I_{rms} and I_{0} are related as$ (1) $I_{rms} = π I_{0}$ (2) $I_{rms} = 2 I_{0}$ (3) $I_{rms} = I_{0} / π$ (4) $I_{rms} = I_{0} / 2$ 259. $An infinitely long, straight wire carrying current I, one side opened rectangular loop and a conductor C with a sliding connector are located in the same plane, as shown, in the figure. The connector has length l and resistance R . It slides to the right with a velocity v . The resistance of the conductor and the self inductance of the loop are negligible. The induced current in the loop, as a function of separation r between the connector and the straight wire is$ (1) $\frac{μ _{0}}{4 π} \frac{Iv l}{Rr}$ (2) $\frac{μ _{0}}{π} \frac{Iv l}{Rr}$ (3) $\frac{μ _{0}}{2 π} \frac{Iv l}{Rr}$ (4) $\frac{2 μ _{0}}{π} \frac{Iv l}{Rr}$ 260. $The self-inductance of a coil depends on$ (1) $number of turns of the coil only$ (2) $size of the coil only$ (3) $shape of the coil only$ (4) $size, shape of the coil and number of turns in it$ 261. $Faraday’s laws are consequence of conservation of$ (1) $energy$ (2) $energy and magnetic field$ (3) $charge$ (4) $magnetic field$ 262. $The energy stored in an inductor of self inductance L henry carrying a current of I ampere is$ (1) $\frac{1}{2} L^{2} I$ (2) $\frac{1}{2} L I^{2}$ (3) $L I^{2}$ (4) $L^{2} I$ 263. $Two coils A and B are placed in a circuit. When current in the coil A changes by 0.8 A the magnetic flux in coil B changes by 0.16 Wb . The mutual inductance between the coils is$ (1) $0.2 H$ (2) $20 H$ (3) $0.5 H$ (4) $2 H$ 264. $The working of magnetic braking of trains is based on$ (1) $steady current$ (2) $eddy current$ (3) $alternating current$ (4) $pulsating current$ 265. $As a result of change in the magnetic flux linked to the closed loop as shown in the figure, an e.m.f. V volt is induced in the loop. The work done (joule) in taking a charge Q coulomb once along the loop is$ (1) $QV$ (2) $2 QV$ (3) $QV /2$ (4) $zero$ 266. $A horizontal straight wire 20 m long extending from east to west falling with a speed of 5.0 m\s, at right angle with the horizontal component of the earth’s magnetic field 0.30 × Wb \ . The instantaneous Value of the e.m. f. induced in the wire will be:$ (1) $3 mV$ (2) $4.5 mV$ (3) $1.5 mV$ (4) $6.0 mV$ 267. $Two insulated circular loop A and B radius ' a' carrying a current of ' I' in the anti clockwise direction as shown in figure. The magnitude of the magnetic induction at the centre will be:$ (1) $\frac{2 μ _{0} I}{a}$ (2) $\frac{μ _{0} I}{2 a}$ (3) $\frac{μ _{0} I}{2 a}$ (4) $\frac{2 μ _{0} I}{a}$ 268. $An ac generator converts$ (1) $electrical energy into mechanical energy.$ (2) $electrical energy into magnetic energy.$ (3) $mechanical energy into magnetic energy.$ (4) $mechanical energy into electrical energy.$ 269. $Self inductance of solenoid is$ (1) $directly proportional to current flowing through the coil.$ (2) $directly proportional to the length.$ (3) $directly proportional to its area of cross-section.$ (4) $inversely proportional to the area of cross-section$ 270. $The Lenz law is associated with$ (1) $law of conservation of charge.$ (2) $law of conservation of mass.$ (3) $law of conservation of angular momentum$ (4) $law of conservation of energy.$