Electromagnetic Induction PYQs Set 7 (PDF)

Set 7 of 11 · Questions 181-210 of 319

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Mere Teacher · Previous Year Questions JEE Main Physics · Electromagnetic Induction · Set 7 (Q181-210)
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181. $A transformer operating at primary voltage 8 kV and secondary voltage 160 V serves a load of 80 kW. Assuming the transformer to be ideal with purely resistive load and working on unity power factor, the loads in the primary and secondary circuit would be$ (1) $800 Ω and 1.06 Ω$ (2) $10 Ω and 500 Ω$ (3) $800 Ω and 0.32 Ω$ (4) $1.06 Ω and 500 Ω$ 182. $A coil of 800 turns effective area 0.05 m^{2} is kept perpendicular to a magnetic field 5 \times 10^{- 5} T . When the plane of the coil is rotated by 90^{\circ} around any of its co-planar axis in 0.1 s, the emf induced in the coil will be [NEET 2019]$ (1) $0.2 V$ (2) $2 \times 10^{- 3} V$ (3) $0.02 V$ (4) $2 V$ 183. $The current in a coil changes from 3 A to 1 A in 0.1 s in coil of self-inductance 8 mH . The emf induced in the coil is$ (1) $16 V$ (2) $1.6\times 1 0^{- 2} V$ (3) $16\times 1 0^{- 2} V$ (4) $2 V$ 184. $A boy is playing with the empty rim of a cycle wheel of radius 40 cm by rolling it along a horizontal road towards north with angular speed of 20 rad s^{- 1} . Considering the effect of magnetic field of earth, the e.m.f induced in the rim is (Horizontal component of earth's magnetic field = 0.26 G)$ (1) $Zero$ (2) $2 μV$ (3) $2.4 mV$ (4) $3 V$ 185. $A horizontal wire of mass ' m', length ' l' and resistance ' R' is sliding on the vertical rails on which uniform magnetic field ' B' is directed perpendicular. The terminal speed of the wire as it falls under the force of gravity is (g = acceleration due to gravity)$ (1) $\frac{mgl}{BR}$ (2) $\frac{B ^{2} l ^{2}}{mgR}$ (3) $\frac{mgR}{Bl}$ (4) $\frac{mgR}{B ^{2} l ^{2}}$ 186. $The self-inductance of a long solenoid of cross-sectional area A, length l and n turns per unit length is given by$ (1) $μ_{0} n Al$ (2) $μ_{0} n^{2} Al$ (3) $μ_{0} n^{2} A^{2} l$ (4) $μ_{0} n^{2} π A^{2} l$ 187. $Assertion (A): When plane of coil is perpendicular to magnetic field, magnetic flux linked with the coil is minimum, but induced emf is zero. Reason (R) : φ = nABco s θ and e = \frac{d φ}{dt}$ (1) $Both A and R are true and R is the correct explanation for A .$ (2) $Both A and R are true but R is not the correct explanation for A .$ (3) $A is true, R is false.$ (4) $A is false, R is true.$ 188. $A jet plane having a wing-span of 25 m is travelling horizontally towards east with a speed of 3600 km / hour . If the Earth's magnetic field at the location is 4 \times 10^{- 4} T and the angle of dip is 30^{\circ}, then the potential difference between the ends of the wing is$ (1) $4 V$ (2) $5 V$ (3) $2 V$ (4) $2.5 V$ 189. $Two conducting circular loops of radii R_{1} and R_{2} are placed in the same plane with their centres coinciding. If R_{1} > R_{2}, the mutual inductance M between them will be directly proportional to$ (1) $\frac{R _{1}}{R _{2}}$ (2) $\frac{R _{2}}{R _{1}}$ (3) $\frac{R _{1}^{2}}{R _{2}}$ (4) $\frac{R _{2}^{2}}{R _{1}}$ 190. $Three identical coils C_{1}, C_{2} and C_{3} are closely placed such that they share a common axis. C_{2} is exactly midway. C_{1} carries current I in anti-clockwise direction while C_{3} carries current I in clockwise direction. An induced current flows through C_{2} will be in clockwise direction when$ (1) $C_{1} moves away from C2 and C_{3} moves towards C2$ (2) $C_{1} and C_{3} move with equal speeds away from C_{2}$ (3) $C_{1} moves towards C2 and C_{3} moves away from C2$ (4) $C_{1} and C_{3} move with equal speeds towards C_{2}$ 191. $When the current through an inductor is changed at from 2 A to 6 A in time 2 s, emf induced in it is 3 V . Then the inductance of the inductor is$ (1) $1.4 H$ (2) $0.8 H$ (3) $1.5 H$ (4) $0.6 H$ 192. $A 12 V battery connected to a coil of resistance 6 Ω through a switch, drives a constant current in the circuit. The switch is opened in 1 ms. The emf induced across the coil is 20 V. The inductance of the coil is:$ (1) $10 mH$ (2) $8 mH$ (3) $5 mH$ (4) $12 mH$ 193. $A velocity selector consists of electric field E = E k and magnetic field B = B j with B=12 mT. The value E required for an electron of energy 728 eV moving along the positive x-axis to pass undeflected is: (Given, mass of electron = 9.1 x 10-31kg)$ (1) $192 k V m^{- 1}$ (2) $192 m V m^{- 1}$ (3) $9600 k V m^{- 1}$ (4) $16 k V m^{- 1}$ 194. $A wheel of 20 metallic spokes each 40 cm long is rotated with a speed of 180 rev / min in a plane normal to the horizontal component of earth's magnetic field H_{e} at a place. If H_{e} = 0.4 G (Gauss) at that place, the induced emf between the axle and the rim of the wheel is$ (1) $192 π \times 10^{- 7} V$ (2) $256 π \times 10^{- 7} V$ (3) $148 π \times 10^{- 7} V$ (4) $110 π \times 10^{- 7} V$ 195. $An iron rod of volume 10^{- 3} m^{3} and relative permeability 1000 is placed as core in a solenoid with 10 turns / cm . If a current of 0.5 A is passed through the solenoid, then the magnetic moment of the rod will be$ (1) $5 \times 10^{2} Am^{2}$ (2) $0.5 \times 10^{2} Am^{2}$ (3) $500 \times 10^{2} Am^{2}$ (4) $50 \times 10^{2} Am^{2}$ 196. $Figure shows a circuit that contains three identical resistors with resistance R = 9.0 Ω each, two identical inductors with inductance L = 2.0 mH each and an ideal battery with emf ε = 18 V. The current ‘i’ through the battery just after the switch closed is$ (1) $2 mA$ (2) $0.2 A$ (3) $2 A$ (4) $4 ampere$ 197. $A small square loop of side 'a' and one turn is placed inside a larger square loop of side b and one turn (b>>a). The two loops are coplanar with their centers coinciding. If a current I is passed in the square loop of side 'b', then the coefficient of mutual inductance between the two loops is:$ (1) $\frac{μ _{0}}{4 π} 82 \frac{a ^{2}}{b}$ (2) $\frac{μ _{0}}{4 π} \frac{8 2}{a}$ (3) $\frac{μ _{0}}{4 π} 82 \frac{b ^{2}}{a}$ (4) $\frac{μ _{0}}{4 π} \frac{8 2}{b}$ 198. $A bar magnet is passing through a conducting loop of radius R with velocity υ . The radius of the bar magnet is such that it just passes through the loop. The induced e.m.f. in the loop can be represented by the approximate curve:$ (1) (2) (3) (4) 199. $A light bulb and an inductor coil are connected to AC source through a key as shown in the figure below. The key is closed and after sometime an iron rod is inserted into the interior of the inductor. The glow of the light bulb [NEET 2020]$ (1) $decreases$ (2) $remains unchanged$ (3) $will fluctuate$ (4) $increases$ 200. $An electron moves on a straight line path XY as shown. The abcd is a coil adjacent in the path of electron. What will be the direction of current, if any induced in the coil?$ (1) $abcd$ (2) $adcb$ (3) $The current will reverse its direction as the electron goes past the coil$ (4) $No current induced$ 201. $The current (I) in the inductance is varying with time according to the plot shown in figure. Which one of the following is the correct variation of voltage with time in the coil?$ (1) (2) (3) (4) 202. $There are two long co-axial solenoids of same length l. The inner and outer coils have radii r_{1} and r_{2} and number of turns per unit length n_{1} and n_{2}, respectively. The ratio of mutual inductance to the self-inductance of the inner-coil is:$ (1) $\frac{n _{2}}{n _{1}} . \frac{r _{2}^{2}}{r _{1}^{2}}$ (2) $\frac{n _{2}}{n _{1}}$ (3) $\frac{n _{1}}{n _{2}}$ (4) $\frac{n _{2}}{n _{1}} . \frac{r _{1}}{r _{2}}$ 203. $An electron moves on a straight line path XY as shown. The abcd is a coil adjacent to the path of electron. What will be the direction of current, if any, induced in the coil?$ (1) $The current will reverse its direction as the electron goes past the coil$ (2) $No current induced$ (3) $abcd$ (4) $adcb$ 204. $Two concentric coplanar circular conducting loops have radii R and r (R ≫ r) . Their mutual inductance is proportional to$ (1) $\frac{r}{R}$ (2) $\frac{R}{r}$ (3) $\frac{r ^{2}}{R}$ (4) $\frac{R ^{2}}{r}$ 205. $Some magnetic flux is changed from a coil of resistance 10 ohm. As a result an induced current is developed in it, which varies with time as shown in figure. The magnitude of change in flux through the coil in weber is$ (1) $2$ (2) $4$ (3) $6$ (4) $None of these$ 206. $Magnetic flux (in weber) in a closed circuit of resistance 20 Ω varies with time t(s) as φ = 8 t^{2} - 9t + 5. The magnitude of the induced current at t = 0.25 s will be______mA$ 207. $A circular coil of radius 8.0cm and 20 turns is rotated about its vertical diameter with an angular speed of 50 r a d s^{- 1} in a uniform horizontal magnetic field of 3.0 x 1 0^{- 2} T. The maximum emf induced the coil will be \dots..x 1 0^{- 2} volt (rounded off to the nearest integer)$ 208. $The current in a coil of self-inductance 2.0 H is increasing according to I = 2sin(t^{2}) A. The amount of energy spent during the period when current changes from 0 to 2A is_______J.$ 209. $A square loop of side 2.0 cm is placed inside a long solenoid that has 50 turns per centimeter and carries a sinusoidally varying current of amplitude 2. 5 A and angular frequency 700 rad s^{- 1} . The central axes of the loop and solenoid coincide. The amplitude of the emf induced in the loop is x \times 10-4 V. The value of x is___________(Take, π = \frac{22}{7})$ 210. $In the given figure the magnetic flux through the loop increases according to the relation φ_{B} (t) = 10 t^{2} + 20 t, where φ_{B} is in milliwebers and t is in seconds. The magnitude of current through R = 2Ω resistor at t = 5s is mA$