Electromagnetic Induction PYQs Set 6 (PDF)

Set 6 of 10 · Questions 151-180 of 274

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Mere Teacher · Previous Year Questions NEET Physics · Electromagnetic Induction · Set 6 (Q151-180)
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151. $A 10 m long horizontal wire extends from North East to South West. It is falling with a speed of 5.0 ms^{- 1}, at right angles to the horizontal component of the earth's magnetic field, of 0.3 \times 10^{- 4} Wb / m^{2} . The value of the induced emf in wire is:$ (1) $1.5 \times 10^{- 3} V$ (2) $1.1 \times 10^{- 3} V$ (3) $2.5 \times 10^{- 3} V$ (4) $0.3 \times 10^{- 3} V$ 152. $A transformer is used to light a 100 W and 110 V lamp from 220 V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately$ (1) $50%$ (2) $90%$ (3) $10%$ (4) $30%$ 153. $What is the value of inductance L for which the current is maximum in a series LCR circuit with C = 10 μF and ω = 1000 s^{- 1} ?$ (1) $1 mH$ (2) $cannot be calculated unless R is known$ (3) $10 mH$ (4) $100 mH$ 154. $The shiny metal disk in the electric power meter (along type) rotates due to$ (1) $temperature change$ (2) $eddy currents$ (3) $an external motor$ (4) $pressure change$ 155. $A uniform magnetic field B is perpendicular to the plane of a circular loop of diameter 10 cm formed from wire of diameter 2 mm and resistivity 2 \times 10^{- 8} Ωm . If a current of 11 A is to be induced in the loop then the rate at which B is to be changed is$ (1) $2.8 T s^{- 1}$ (2) $1.4 T s^{- 1}$ (3) $3.2 T s^{- 1}$ (4) $2.4 T s^{- 1}$ 156. $Two coils P and Q are kept near each other. When no current flows through coil P and current increases in coil Q at the rate 10 A/s, the e.m.f. in coil P is 15mV. When coil Q carries no current and current of 1.8 A flows through coil P, the magnetic flux linked with the coil Q is$ (1) $1.4mWb$ (2) $2.2mWb$ (3) $2.7mWb$ (4) $2.9 mWb$ 157. $A power transmission line feeds input power at 2300 V a step down transformer with its primary windings having 4000 turns. The output power is delivered at 230 V by the transformer. If the current in the primary of the transformer is 5A and its efficiency is 90%, the output current would be:$ (1) $50 A$ (2) $45A$ (3) $35 A$ (4) $25 A$ 158. $A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by 60º is W. Now the torque required to keep the magnet in this new position is:$ (1) $\frac{2 W}{3}$ (2) $\frac{W}{3}$ (3) $3 W$ (4) $\frac{3 W}{2}$ 159. $A very long solenoid of radius R is carrying current I (t) = kt e^{- αt} (k > 0), as a function function of time (t \geq 0) . counter clockwise current is taken to be positive. A circular conducting coil of radius 2 R is placed in the equatorial plane of the solenoid and concentric with the solenoid. The current induced in the outer coil is correctly depicted, as a function of time, by:$ (1) (2) (3) (4) 160. $If flux is given as φ = 3 t^{2} + 4 t + 8 . Then find the induced emf at t = 2 s$ (1) $16 V$ (2) $12 V$ (3) $8 V$ (4) $4 V$ 161. $A transformer operating at primary voltage 8 kV and secondary voltage 160 V serves a load of 80 kW. Assuming the transformer to be ideal with purely resistive load and working on unity power factor, the loads in the primary and secondary circuit would be$ (1) $800 Ω and 1.06 Ω$ (2) $10 Ω and 500 Ω$ (3) $800 Ω and 0.32 Ω$ (4) $1.06 Ω and 500 Ω$ 162. $A coil of 800 turns effective area 0.05 m^{2} is kept perpendicular to a magnetic field 5 \times 10^{- 5} T . When the plane of the coil is rotated by 90^{\circ} around any of its co-planar axis in 0.1 s, the emf induced in the coil will be [NEET 2019]$ (1) $0.2 V$ (2) $2 \times 10^{- 3} V$ (3) $0.02 V$ (4) $2 V$ 163. $The current in a coil changes from 3 A to 1 A in 0.1 s in coil of self-inductance 8 mH . The emf induced in the coil is$ (1) $16 V$ (2) $1.6\times 1 0^{- 2} V$ (3) $16\times 1 0^{- 2} V$ (4) $2 V$ 164. $A boy is playing with the empty rim of a cycle wheel of radius 40 cm by rolling it along a horizontal road towards north with angular speed of 20 rad s^{- 1} . Considering the effect of magnetic field of earth, the e.m.f induced in the rim is (Horizontal component of earth's magnetic field = 0.26 G)$ (1) $Zero$ (2) $2 μV$ (3) $2.4 mV$ (4) $3 V$ 165. $A horizontal wire of mass ' m', length ' l' and resistance ' R' is sliding on the vertical rails on which uniform magnetic field ' B' is directed perpendicular. The terminal speed of the wire as it falls under the force of gravity is (g = acceleration due to gravity)$ (1) $\frac{mgl}{BR}$ (2) $\frac{B ^{2} l ^{2}}{mgR}$ (3) $\frac{mgR}{Bl}$ (4) $\frac{mgR}{B ^{2} l ^{2}}$ 166. $The self-inductance of a long solenoid of cross-sectional area A, length l and n turns per unit length is given by$ (1) $μ_{0} n Al$ (2) $μ_{0} n^{2} Al$ (3) $μ_{0} n^{2} A^{2} l$ (4) $μ_{0} n^{2} π A^{2} l$ 167. $Assertion (A): When plane of coil is perpendicular to magnetic field, magnetic flux linked with the coil is minimum, but induced emf is zero. Reason (R) : φ = nABco s θ and e = \frac{d φ}{dt}$ (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) $A is false, R is true.$ 168. $A jet plane having a wing-span of 25 m is travelling horizontally towards east with a speed of 3600 km / hour . If the Earth's magnetic field at the location is 4 \times 10^{- 4} T and the angle of dip is 30^{\circ}, then the potential difference between the ends of the wing is$ (1) $4 V$ (2) $5 V$ (3) $2 V$ (4) $2.5 V$ 169. $Two conducting circular loops of radii R_{1} and R_{2} are placed in the same plane with their centres coinciding. If R_{1} > R_{2}, the mutual inductance M between them will be directly proportional to$ (1) $\frac{R _{1}}{R _{2}}$ (2) $\frac{R _{2}}{R _{1}}$ (3) $\frac{R _{1}^{2}}{R _{2}}$ (4) $\frac{R _{2}^{2}}{R _{1}}$ 170. $Three identical coils C_{1}, C_{2} and C_{3} are closely placed such that they share a common axis. C_{2} is exactly midway. C_{1} carries current I in anti-clockwise direction while C_{3} carries current I in clockwise direction. An induced current flows through C_{2} will be in clockwise direction when$ (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) $C_{1} and C_{3} move with equal speeds towards C_{2}$ 171. $When the current through an inductor is changed at from 2 A to 6 A in time 2 s, emf induced in it is 3 V . Then the inductance of the inductor is$ (1) $1.4 H$ (2) $0.8 H$ (3) $1.5 H$ (4) $0.6 H$ 172. $A 12 V battery connected to a coil of resistance 6 Ω through a switch, drives a constant current in the circuit. The switch is opened in 1 ms. The emf induced across the coil is 20 V. The inductance of the coil is:$ (1) $10 mH$ (2) $8 mH$ (3) $5 mH$ (4) $12 mH$ 173. $A velocity selector consists of electric field E = E k and magnetic field B = B j with B=12 mT. The value E required for an electron of energy 728 eV moving along the positive x-axis to pass undeflected is: (Given, mass of electron = 9.1 x 10-31kg)$ (1) $192 k V m^{- 1}$ (2) $192 m V m^{- 1}$ (3) $9600 k V m^{- 1}$ (4) $16 k V m^{- 1}$ 174. $A wheel of 20 metallic spokes each 40 cm long is rotated with a speed of 180 rev / min in a plane normal to the horizontal component of earth's magnetic field H_{e} at a place. If H_{e} = 0.4 G (Gauss) at that place, the induced emf between the axle and the rim of the wheel is$ (1) $192 π \times 10^{- 7} V$ (2) $256 π \times 10^{- 7} V$ (3) $148 π \times 10^{- 7} V$ (4) $110 π \times 10^{- 7} V$ 175. $An iron rod of volume 10^{- 3} m^{3} and relative permeability 1000 is placed as core in a solenoid with 10 turns / cm . If a current of 0.5 A is passed through the solenoid, then the magnetic moment of the rod will be$ (1) $5 \times 10^{2} Am^{2}$ (2) $0.5 \times 10^{2} Am^{2}$ (3) $500 \times 10^{2} Am^{2}$ (4) $50 \times 10^{2} Am^{2}$ 176. $Figure shows a circuit that contains three identical resistors with resistance R = 9.0 Ω each, two identical inductors with inductance L = 2.0 mH each and an ideal battery with emf ε = 18 V. The current ‘i’ through the battery just after the switch closed is$ (1) $2 mA$ (2) $0.2 A$ (3) $2 A$ (4) $4 ampere$ 177. $A small square loop of side 'a' and one turn is placed inside a larger square loop of side b and one turn (b>>a). The two loops are coplanar with their centers coinciding. If a current I is passed in the square loop of side 'b', then the coefficient of mutual inductance between the two loops is:$ (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) $\frac{μ _{0}}{4 π} \frac{8 2}{b}$ 178. $A bar magnet is passing through a conducting loop of radius R with velocity υ . The radius of the bar magnet is such that it just passes through the loop. The induced e.m.f. in the loop can be represented by the approximate curve:$ (1) (2) (3) (4) 179. $A light bulb and an inductor coil are connected to AC source through a key as shown in the figure below. The key is closed and after sometime an iron rod is inserted into the interior of the inductor. The glow of the light bulb [NEET 2020]$ (1) $decreases$ (2) $remains unchanged$ (3) $will fluctuate$ (4) $increases$ 180. $An electron moves on a straight line path XY as shown. The abcd is a coil adjacent in the path of electron. What will be the direction of current, if any induced in the coil?$ (1) $abcd$ (2) $adcb$ (3) $The current will reverse its direction as the electron goes past the coil$ (4) $No current induced$