Moving Charges & Magnetism PYQs Set 11 (PDF)

Set 11 of 17 · Questions 301-330 of 499

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Mere Teacher · Previous Year Questions NEET Physics · Moving Charges & Magnetism · Set 11 (Q301-330)
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301. $A coaxial cable consists of an inner wire of radius 'a' surrounded by an outer shell of inner and outer radii 'b' and 'c' respectively. The inner wire carries an electric current i_{0}, which is distributed uniformly across crosssectional area. The outer shell carries an equal current in opposite direction and distributed uniformly. What will be the ratio of the magnetic field at a distance from the axis when (i) x < a and (ii) a < x < b?$ (1) $\frac{x ^{2}}{a ^{2}}$ (2) $\frac{a ^{2}}{x ^{2}}$ (3) $\frac{x ^{2}}{b ^{2} - a ^{2}}$ (4) $\frac{b ^{2} - a ^{2}}{x ^{2}}$ 302. $In the given figure, the magnetic field at O .$ (1) $\frac{3}{8} \frac{μ _{0} I}{r} + \frac{μ _{0} I}{4 πr}$ (2) $\frac{3}{8} \frac{μ _{0} I}{r} - \frac{μ _{0} I}{4 πr}$ (3) $\frac{3}{4} \frac{μ _{0} I}{r} + \frac{μ _{0} I}{4 πr}$ (4) $\frac{3}{10} \frac{μ _{0} I}{r} - \frac{μ _{0} I}{4 πr}$ 303. $A very long conducting wire is bent in a semi-circular shape from A to B as shown in figure. The magnetic field at point P for steady current configuration is given by [NEET 2023]$ (1) $\frac{μ _{0} i}{4 R} pointed away from the page$ (2) $\frac{μ _{0} i}{4 R} (1 - \frac{2}{π}) pointed away from page$ (3) $\frac{μ _{0} i}{4 R} (1 - \frac{2}{π}) pointed into the page$ (4) $\frac{μ _{0} i}{4 R} pointed into the page$ 304. $A massless square loop, of wire of resistance 10 Ω . supporting a mass of 1 g. hangs vertically with one of its sides in a uniform magnetic field of 103 G_{;} directed outwards in the shaded region, A dc voltage V is applied to the loop. For what value of V, the magnetic force will exactly balance the weight of the supporting mass of 1g? (If sides of the loop =10 cm, g = 10 m s^{2})$ (1) $\frac{1}{10} V$ (2) $100 V$ (3) $1 V$ (4) $10 V$ 305. $Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2 I, respectively The resultant magnetic field induction at the centre will be$ (1) $\frac{5 μ _{0} I}{2 R}$ (2) $\frac{5 μ _{0} I}{R}$ (3) $\frac{μ _{0} I}{2 R}$ (4) $\frac{μ _{0} I}{R}$ 306. $A rigid square of loop of side ’ a ’ and carrying current I_{2} is lying on a horizontal surface near a long current I_{1} carrying wire in the same plane as shown in figure. The net force on the loop due to the wire will be:$ (1) $Repulsive and equal to \frac{μ _{o} I _{1} I _{2}}{2 π}$ (2) $Attractive and equal to \frac{μ _{o} I _{1} I _{2}}{3 π}$ (3) $Repulsive and equal to \frac{μ _{o} I _{1} I _{2}}{4 π}$ (4) $Zero$ 307. $A horizontal wire carries 160 A current below which another wire of linear density 10 g / m carrying a current is kept at 4 cm distance. If the wire is kept below hangs in air, what is the current in this wire when the direction of current in both the wires is same? (= 10 m / s^{2} and μ_{0} = 4 π \times 10^{- 7})$ (1) $125 A$ (2) $140 A$ (3) $110 A$ (4) $100 A$ 308. $A loop of flexible conducting wire lies in a magnetic field of 2.0 T with its plane perpendicular to the field. The length of the wire is 1 m . When a current of 1.1 A is passed through the loop, it opens into a circle, then the tension developed in the wire is$ (1) $0.15 N$ (2) $0.25 N$ (3) $0.35 N$ (4) $0.45 N$ 309. $An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has magnitude$ (1) $\frac{μ _{0} ne}{2 πr}$ (2) $zero$ (3) $\frac{μ _{0} n ^{2} e}{r}$ (4) $\frac{μ _{0} ne}{2 r}$ 310. $A long wire carrying a steady current is bent into a circular loop of one turn. The magnetic field at the center of the loop is B. It is then bent into a circular coil of n turns. The magnetic field at the center of this coil of n turns will be [NEET 2016]$ (1) $nB$ (2) $n^{2} B$ (3) $2nB$ (4) $2 n^{2} B$ 311. $What is the net force on the square coil?$ (1) $25\times 1 0^{- 7} N moving towards wire$ (2) $25\times 1 0^{- 7} N moving away from wire$ (3) $35 \times 10^{- 7} N moving towards wire$ (4) $35 \times 10^{- . 7} N moving away from wire$ 312. $A square loop of side ' a' and carrying a current ' I' is suspended from an insulting hanger of a spring balance as shown in the figure. The transverse magnetic field 'B' directed into the paper occurs only at the bottom side of the loop. When direction of current in the loop is reversed, the change in the reading of spring balance is$ (1) $IaB$ (2) $2 IaB$ (3) $IaB 2$ (4) $\frac{3}{2} IaB$ 313. $Two identical long conducting wires AOB and COD are placed at right angle to each other, such that one is above the other and O is their common point. The wires carry I_{1} and I_{2} currents, respectively. Point P is lying at distance d from O along a direction perpendicular to the plane containing the wires. The magnetic field at the point P will be$ (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) $\frac{μ _{0}}{2 πd} (I_{1}^{2} + I_{2}^{2})^{1/2}$ 314. $Two very long, straight, and insulated wires are kept at 90^{\circ} angle from each other in xy -plane as shown in the figure. These wires carry currents of equal magnitude I, whose directions are shown in the figure. The net magnetic field at point P will be:$ (1) $Zero$ (2) $- \frac{μ _{0} I}{2 πd} (x + y)$ (3) $\frac{+ μ _{0} I}{πd} (z)$ (4) $\frac{μ _{0} I}{2 πd} (x + y)$ 315. $A conducting square frame of side ‘a’ and a long straight wire carrying current I arelocated in the same plane as shown in the figure. The frame moves to the right with a constant velocity ‘V. The emf induced in the frame will be proportional to$ (1) $\frac{1}{( 2 x + a ) ^{2}}$ (2) $\frac{1}{( 2 x - a ) ( 2 x + a )}$ (3) $\frac{1}{x ^{2}}$ (4) $\frac{1}{( 2 x - a ) ^{2}}$ 316. $The magnetic field of given length of wire for single turn coil at its center is B then its value for two turns coil for the same wire is$ (1) $B /4$ (2) $B /2$ (3) $4 B$ (4) $2 B$ 317. $Two ions of masses 4amu and 16 amu have charges +2e and +3e respectively. These ions pass through the region of constant perpendicular magnetic field. The kinetic energy of both ions is same. Then:$ (1) $lighter ion will be deflected less than heavier ion$ (2) $lighter ion will be deflected more than heavier ion$ (3) $both ions will be deflected equally$ (4) $no ion will be deflected.$ 318. $The magnetic field at the center C of the arrangement shown in figure is$ (1) $\frac{μ _{0} i}{2 πr} (1 + π)$ (2) $\frac{μ _{0} i}{4 πr} (1 + π)$ (3) $\frac{μ _{0} i}{πr} (1 + π)$ (4) $\frac{μ _{0} i}{r} (1 + π)$ 319. $A wire A, bent in the shape of an arc of a circle, carrying a current of 2 A and having radius 2 cm and another wire B also bent in the shape of arc of a circle, carrying a current of 3 A and having radius of 4 cm are placed as shown in the figure. The ratio of the magnetic fields due to the wires A and B at the common centre O is$ (1) $02: 05$ (2) $06: 05$ (3) $04: 06$ (4) $06: 04$ 320. $A circular coil ABCD carrying a current ‘i’ is placed in a uniform magnetic field. If the magnetic force on the segment AB is F, the force on the remaining segment BCDA is$ (1) $- F$ (2) $3 F$ (3) $- 3 F$ (4) $F .$ 321. $A current I = 5 A flows along a thin wire shaped as shown in figure. The radius of curved part of the wire is equal to R = 100 mm, the angle 2 φ = 90^{\circ} . The magnitude of magnetic field at the point O is approximately (Use \frac{μ _{0}}{4 π} = 10^{- 7} TmA^{- 1})$ (1) $33.6 μT$ (2) $38.4 μT$ (3) $48.7 μT$ (4) $25.2 μT$ 322. $A certain current on passing through a galvanometer produces a deflection of 100 divisions. When a shunt of one ohm is connected, the deflection reduces to 1 division. The galvanometer resistance is$ (1) $10Ω$ (2) $9.9Ω$ (3) $100Ω$ (4) $99Ω$ 323. $A charged particle (mass m and charge q) moves along x -axis with velocity V_{0} . When it passes through the origin it enters a region having uniform electric field E \to= - E j^which extends upto x = d Equation of path of electron in the region x > d is$ (1) $y = \frac{qEd}{m V _{0}^{2}} (x - d)$ (2) $y = \frac{qEd ^{2}}{mV _{0}^{2}} x$ (3) $y = \frac{qEd}{mV _{0}^{2}} (\frac{d}{2} - x)$ (4) $y = \frac{qEd}{m V _{0}^{2}} x$ 324. $N equally spaced charges each of value q, are placed on a circle of radius R. The circle rotates about its axis with an angular velocity ω as shown in the figure. A bigger Amperian loop B encloses the whole circle where as a smaller Amperian loop A encloses a small segment. The difference between enclosed currents, I_{A} - I_{B}, for the given Amperian loops is$ (1) $\frac{2 π}{N} qω$ (2) $\frac{N ^{2}}{2 π} qω$ (3) $\frac{N}{π} qω$ (4) $\frac{N}{2 π} qω$ 325. $When a proton is released from rest in a room, it starts with an initial acceleration a0 towards west. When it is projected towards north with a speed v0 it moves with an initial acceleration 3 a_{0} toward west. The electric and magnetic fields in the room are$ (1) $\frac{m a _{0}}{e} east, \frac{3 m a _{0}}{e v _{0}} up$ (2) $\frac{m a _{0}}{e} east, \frac{3 m a _{0}}{e v _{0}} down$ (3) $\frac{m a _{0}}{e} west, \frac{2 m a _{0}}{e ν _{0}} up$ (4) $\frac{m a _{0}}{e} west, \frac{2 m a _{0}}{e v _{0}} down.$ 326. $Two parallel wires 1 m apart carry currents of 1 A and 3 A respectively in opposite directions. The force per unit length acting between these two wires is$ (1) $6\times 1 0^{- 7} N m-1 attractive$ (2) $6\times 1 0^{- 5} N m-1 attractive$ (3) $6\times 1 0^{- 7} N m-1 repulsive$ (4) $6\times 1 0^{- 5} N m-1 repulsive$ 327. $A galvanometer of resistance, G, is shunted by a resistance S ohm. To keep the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is$ (1) $\frac{G}{( S + G )}$ (2) $\frac{S ^{2}}{( S + G )}$ (3) $\frac{SG}{( S + G )}$ (4) $\frac{G ^{2}}{( S + G )}$ 328. $A wire PQR is bent as shown in figure and is placed in a region of uniform magnetic field B . The length of PQ = QR = l . A current I ampere flows through the wire as shown. The magnitude of the force on PQ and QR will be$ (1) $BIl, 0$ (2) $2 BIl, 0$ (3) $0, BIl$ (4) $0,0$ 329. $A loop of flexible wire or irregular shape carrying current is placed in an external magnetic field. Identify the effect of the field on the wire.$ (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) $shape of the loop remains unchanged$ 330. $Let B_{1} be the magnitude of magnetic field at center of a circular coil of radius R carrying current I . Let B_{2} be the magnitude of magnetic field at an axial distance ' x' from the center. For x : R = 3 : 4, \frac{B _{2}}{B _{1}} is:$ (1) $64 : 125$ (2) $25 : 16$ (3) $4 :5$ (4) $16 : 25$