Moving Charges & Magnetism PYQs Set 13 (PDF)

Set 13 of 19 · Questions 361-390 of 549

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Mere Teacher · Previous Year Questions JEE Main Physics · Moving Charges & Magnetism · Set 13 (Q361-390)
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361. $A wire PQR is bent as shown in figure and is placed in a region of uniform magnetic field B . The length of PQ = QR = l . A current I ampere flows through the wire as shown. The magnitude of the force on PQ and QR will be$ (1) $BIl, 0$ (2) $2 BIl, 0$ (3) $0, BIl$ (4) $0,0$ 362. $A loop of flexible wire or irregular shape carrying current is placed in an external magnetic field. Identify the effect of the field on the wire.$ (1) $loop assumes circular shape with its plane normal to the field$ (2) $wire gets stretched to become straight$ (3) $loop assumes circular shape with its plane parallel to the field$ (4) $shape of the loop remains unchanged$ 363. $Let B_{1} be the magnitude of magnetic field at center of a circular coil of radius R carrying current I . Let B_{2} be the magnitude of magnetic field at an axial distance ' x' from the center. For x : R = 3 : 4, \frac{B _{2}}{B _{1}} is:$ (1) $64 : 125$ (2) $25 : 16$ (3) $4 :5$ (4) $16 : 25$ 364. $A straight wire carrying a current of 12 A is bent into a semi-circular arc of radius 2 cm as shown in the figure. Then the magnetic field due to the straight segments at the centre of the arc is$ (1) $12 T$ (2) $6 T$ (3) $24 T$ (4) $0$ 365. $In a uniform magnetic field of 0.049 T, a magnetic needle performs 20 complete oscillations in 5 s as shown. The moment of inertia of the needle is 9.8 \times 10^{- 6} kg m^{2} . If the magnitude of magnetic moment of the needle is x \times 10^{- 5} Am^{2}, then the value of x is [NEET 2024]$ (1) $5 π^{2}$ (2) $128 π^{2}$ (3) $50 π^{2}$ (4) $1280 π^{2}$ 366. $Two identical circular loops P and Q each of radius r are lying in parallel planes such that they have common axis. The current through P and Q are I and 4 I respectively in clockwise direction as seen from O . The net magnetic field at O is:$ (1) $\frac{3 μ _{0} I}{4 2 r} towards Q$ (2) $\frac{μ _{o} I}{4 2 r} towards Q$ (3) $\frac{3 μ _{0} I}{4 2 r} towards P$ (4) $\frac{μ _{o} I}{4 2 r} towards P$ 367. $The resultant force on the current loop PQRS due to a long current carrying conductor will be$ (1) $1.8\times 1 0^{- 4} N$ (2) $5\times 1 0^{- 4} N$ (3) $10^{- 4} N$ (4) $3.6\times 1 0^{- 4} N$ 368. $A cylindrical conductor of radius R is carrying a constant current. The plot of the magnitude of the magnetic field B with the distance d from the center of the conductor, is correctly represented by the figure [NEET 2019]$ (1) (2) (3) (4) 369. $Magnitude of magnetic field (in SI units) at thecentre of a hexagonal shape coil of side 10 cm, 50 turns and carrying current I (Ampere) in units of \frac{μ _{0} I}{π} is$ (1) $5003$ (2) $2503$ (3) $503$ (4) $53$ 370. $A circular coil having N turns and radius r carries a current I . It is held in the XZ plane in a magnetic field B i . The torque on the coil due to the magnetic field is:$ (1) $\frac{B r ^{2} I}{πN}$ (2) $Bπ r^{2} IN$ (3) $\frac{Bπ r ^{2} I}{N}$ (4) $Zero$ 371. $The magnetic field in a region is given by B = B_{0} (\frac{x}{a}) k . A square loop of side d is placed with its edgesalong the x and y axes. The loop is moved with a constant velocity v = v_{0} i . The emf induced in the loop is:$ (1) $\frac{B _{0} v _{0}^{2} d}{2 a}$ (2) $\frac{B _{0} v _{0} d}{2 a}$ (3) $\frac{B _{0} v _{0} d ^{2}}{a}$ (4) $\frac{B _{0} v _{0} d ^{2}}{2 a}$ 372. $A current of 1 A is flowing on the sides of an equilateral triangle of side 4.5 \times 10^{- 2} m . The magnetic field at the centre of the triangle will be$ (1) $4 \times 10^{- 5} Wb / m^{2}$ (2) $8 \times 10^{- 5} Wb / m^{2}$ (3) $2 \times 10^{- 5} Wb / m^{2}$ (4) $Zero$ 373. $A neutron, a proton, an electron and an α -particle enter a region of uniform magnetic field with the same velocities. The magnetic field is perpendicular and directed into the plane of the paper. The tracks of the particles are labelled in the figure. The electron follows the track$ (1) $A$ (2) $B$ (3) $C$ (4) $D$ 374. $From Ampere's circuital law for a long straight wire of circular cross-section carrying a steady current, the variation of magnetic field in the inside and outside region of the wire is [NEET 2022]$ (1) $a linearly increasing function of distance upto the boundary of the wire and then linearly decreasing for the outside region.$ (2) $a linearly increasing function of distance r upto the boundary of the wire and then decreasing one with 1/r dependence for the outside region.$ (3) $a linearly decreasing function of distance upto the boundary of the wire and then a linearly increasing one for the outside region.$ (4) $uniform and remains constant for both the regions.$ 375. $A galvanometer of resistance 30Ω is connected to a battery of emf 2 V with 1970Ω resistance in series. A full scale deflection of 20 divisions is obtained in the galvanometer. To reduce the deflection to 10 divisions, the resistance in series required is$ (1) $4030Ω$ (2) $4000Ω$ (3) $3970Ω$ (4) $2000Ω$ 376. $A charged particle going around in a circle can be considered to be a current loop. A particle of mass m carrying charge q is moving in a plane with speed v under the influence of magnetic field B . The magnetic moment of this moving particle:$ (1) $- \frac{m v ^{2} B \to}{2 B ^{2}}$ (2) $\frac{m v ^{2} B \to}{2 B ^{2}}$ (3) $- \frac{m v ^{2} B \to}{2 π B ^{2}}$ (4) $- \frac{m v ^{2} B \to}{B ^{2}}$ 377. $Three long straight wires carrying current are arranged mutually parallel as shown in the figure. The force experienced by 15 cm length of wire Q is____. (μ_{o} = 4 π \times 10^{- 7} T . m / A)$ (1) $6\times 1 0^{- 6} N towards P$ (2) $6\times 1 0^{- 7} N towards P$ (3) $6\times 1 0^{- 7} N towards R$ (4) $6\times 1 0^{- 6} N towards R$ 378. $Two parallel, long wires are kept 0.20 m apart in vacuum, each carrying current of x A in the same direction. If the force of attraction per meter of each wire is 2 x 1 0^{- 6} N, then the value of x is approximately:$ (1) $1$ (2) $2.4$ (3) $1.4$ (4) $2$ 379. $A conducting wire carrying current is arranged as shown. The magnetic field at O$ (1) $\frac{μ _{0} i}{12} (\frac{1}{R _{1}} - \frac{1}{R _{2}})$ (2) $\frac{μ _{0} i}{12} (\frac{1}{R _{1}} + \frac{1}{R _{2}})$ (3) $\frac{μ _{0} i}{6} (\frac{1}{R _{1}} - \frac{1}{R _{2}})$ (4) $\frac{μ _{0} i}{6} (\frac{1}{R _{1}} + \frac{1}{R _{2}})$ 380. $A long straight wire carrying current 16 A is bent at 90^{\circ} such that half of the wire lies along the positive x -axis and other half lies along the positive y -axis. What is the magnitude of the magnetic field at the point, r = (- 2 i + 0 j) mm ? (Assume, \frac{μ _{0}}{4 π} = 10^{- 7} Hm^{- 1})$ (1) $1.2 mT$ (2) $0.8 mT$ (3) $3.2 mT$ (4) $1.6 mT$ 381. $An electron gun is placed inside a long solenoid of radius R on its axis. The solenoid has n turns/length and carries a current I . The electron gun shoots an electron along the radius of the solenoid with speed v . If the electron does not hit the surface of the solenoid, maximum possible value of v is (all symbols have their standard meaning)$ (1) $\frac{e μ _{0} nIR}{2 m}$ (2) $\frac{e μ _{0} nIR}{m}$ (3) $\frac{2 e μ _{0} nIR}{m}$ (4) $\frac{e μ _{0} nIR}{4 m}$ 382. $An electron is projected with uniform velocity along the axis inside a current carrying long solenoid. Then:$ (1) $the electron will continue to move with uniform velocity along the axis of the solenoid.$ (2) $the electron will be accelerated along the axis.$ (3) $the electron path will be circular about the axis.$ (4) $the electron will experience a force at 45^{\circ} to the axis and execute a helical path.$ 383. $An electron is moving along + x direction with a velocity of 6 \times 10^{6} ms^{- 1} . It enters a region of uniform electric field of 300 V / cm pointing along + y direction. The magnitude and direction of the magnetic field set up in this region such that the electron keeps moving along the x direction will be$ (1) $5\times 1 0^{- 3} T along +z direction$ (2) $5\times 1 0^{- 3} T along -z direction$ (3) $5\times 1 0^{- 4} T along +z direction$ (4) $5\times 1 0^{- 4} T along -z direction$ 384. $A triangular shaped wire carrying 10A current is placed in a uniform magnetic field of 0.5T, as shown in figure. The magnetic force on segment CD is (Given BC = CD = BD = 5 cm).$ (1) $0.126N$ (2) $0.312N$ (3) $0.216N$ (4) $0.245 N$ 385. $A straight conductor carrying current i splits into two parts as shown in the figure. The radius of the circular loop is R. The total magnetic field at the center P at the loop is [NEET 2019]$ (1) $zero$ (2) $3 μ_{0} i /32 R, outward$ (3) $3 μ_{0} i /32 R, inward$ (4) $\frac{μ _{0} i}{2 R}, inward$ 386. $A very long wire A B D M N D C is shown in figure carrying current i . A B and B C parts are straight, long and at right angle. At D wire forms a circular turn D M N D of radius R . A B, B C parts are tangential to circular turn at N and D . Magnetic field at the center of circle is :$ (1) $\frac{μ _{0} i}{2 πR} (\frac{- 1}{2} + π)$ (2) $\frac{μ _{0} i}{2 πR} [π - 1]$ (3) $\frac{μ _{0} i}{2 R}$ (4) $\frac{μ _{0} i}{2 πR} (\frac{1}{2} + π)$ 387. $Two identical long conducting wires AOB and COD are placed at right angle to each other, with one above other such that 'O' is their common point for the two. The wires carry I_{1} and I_{2} currents, respectively. Point 'I' is lying at distance 'd' from 'O' along a direction perpendicular to the plane containing the wires. The magnetic field at the point 'P' will be:$ (1) $\frac{μ _{0}}{2 πd} (\frac{I _{1}}{I _{2}})$ (2) $\frac{μ _{0}}{2 πd} (I_{1} + I_{2})$ (3) $\frac{μ _{0}}{2 πd} (I_{1}^{2} - I_{2}^{2})$ (4) $\frac{μ _{0}}{2 πd} (I_{1}^{2} + I_{2}^{2})^{1/2}$ 388. $As shown in the figure, a long straight conductor with semicircular arc of radius \frac{π}{10} m is carrying current I = 3A. The magnitude of the magnetic field, at the center O of the arc is: (The permeability of the vacuum = 4 π \times 1 0^{- 7} N A^{- 2})$ (1) $6 µT$ (2) $l µT$ (3) $4 µT$ (4) $3 µT$ 389. $A straight magnetic strip has a magnetic moment of 44 Am^{2} . If the strip is bent in a semicircular shape, its magnetic moment will be ______Am^{2} . (given π = \frac{22}{7})$ 390. $A regular polygon of 6 sides is formed by bending a wire of length 4 π meter. If an electric current of 4 π 3 A is flowing through the sides of the polygon, the magnetic field at the centre of the polygon would be x \times 10^{- 7} T . The value of x is____$