Moving Charges & Magnetism PYQs Set 10 (PDF)

Set 10 of 17 · Questions 271-300 of 499

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Mere Teacher · Previous Year Questions NEET Physics · Moving Charges & Magnetism · Set 10 (Q271-300)
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271. $A very long straight wire carries a current I . At the instant when a charge + Q at point P has velocity v, as shown, the force on the charge is$ (1) $along Oy$ (2) $opposite to Oy$ (3) $along Ox$ (4) $opposite to Ox.$ 272. $A thick current carrying cable of radius R carries current I uniformly distributed across its cross-section. The variation of magnetic field B due to the cable with the distance r from the axis of the cable is represented by [NEET 2021]$ (1) (2) (3) (4) 273. $Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2 I, respectively. The resultant magnetic field induction at the centre will be:$ (1) $\frac{5 μ _{0} I}{2 R}$ (2) $\frac{3 μ _{0} I}{2 R}$ (3) $\frac{μ _{0} I}{2 R}$ (4) $\frac{μ _{0} I}{R}$ 274. $An arrangement of three parallel straight wires placed perpendicular to plane of paper carrying same current I along the same direction is shown in figure. Magnitude of force per unit length on the middle wire B is given by [NEET 2017]$ (1) $\frac{μ _{0} I ^{2}}{2 πd}$ (2) $\frac{2 μ _{0} I ^{2}}{πd}$ (3) $\frac{2 μ _{0} I ^{2}}{πd}$ (4) $\frac{μ _{0} I ^{2}}{2 πd}$ 275. $An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the center has magnitude:$ (1) $Zero$ (2) $\frac{μ _{0} n ^{2} e}{r}$ (3) $\frac{μ _{0} ne}{2 r}$ (4) $\frac{μ _{0} ne}{2 πr}$ 276. $An infinitely long hollow conducting cylinder with radius R carries a uniform current along its surface. Choose the correct representation of magnetic field (b) as a function of radial distance (r) from the axis of cylinder.$ (1) (2) (3) (4) 277. $A wire carrying current I has the shape as shown in adjoining figure. Linear parts of the wire are very long and parallel to X ‐axis while semicircular portion of radius R is lying in Y‐Z plane. Magnetic field at point O is$ (1) $B = - \frac{μ _{0}}{4 π} \frac{I}{R} (π i + 2 k)$ (2) $B = \frac{μ _{0}}{4 π} \frac{I}{R} (π i - 2 k)$ (3) $B = \frac{μ _{0}}{4 π} \frac{I}{R} (π i + 2 k)$ (4) $B = - \frac{μ _{0}}{4 π} \frac{I}{R} (π i - 2 k) .$ 278. $In the loop shown, the magnetic induction at the point ' O' is$ (1) $\frac{μ _{0} I}{8} (\frac{R _{1} - R _{2}}{R _{1} R _{2}})$ (2) $\frac{μ _{0} I}{8} (\frac{R _{1} + R _{2}}{R _{1} R _{2}})$ (3) $\frac{μ _{0} I}{8} (\frac{R _{1} R _{2}}{R _{1} + R _{2}})$ (4) $zero$ 279. $A small block of mass 20 g and charge 4 mC is released on a long smooth inclined plane of inclination angle of 45^{\circ}, A uniform horizontal magnetic field of 1 T is acting parallel to the surface, as shown in the figure. The time from the start when the block loses contact with the surface of the plane is$ (1) $2 s$ (2) $3 s$ (3) $5 s$ (4) $6 s$ 280. $An arrangement of three parallel straight wires placed perpendicular to plane of paper carrying same current ‘ I along the same direction as shown in figure. Magnitude of force per unit length on the middle wire‘ B ’ is given by$ (1) $\frac{2 μ _{0} I ^{2}}{π d}$ (2) $\frac{2 μ _{0} I ^{2}}{π d}$ (3) $\frac{μ _{0} I ^{2}}{2 π d}$ (4) $\frac{μ _{0} I ^{2}}{2 π d}$ 281. $Two infinitely long wires carry currents 4 A and 3 A placed along X -axis and Y -axis respectively. Magnetic field at a point P (0, 0, d) m will be ...... T.$ (1) $\frac{4 μ _{0}}{2 πd}$ (2) $\frac{3 μ _{0}}{2 πd}$ (3) $\frac{7 μ _{0}}{2 πd}$ (4) $\frac{5 μ _{0}}{2 πd}$ 282. $A hairpin like shape as shown in figure is made by bending a long current carrying wire. What is the magnitude of a magnetic field at point P which lies on the centre of the semicircle?$ (1) $\frac{μ _{0} I}{4 πr} (2 - π)$ (2) $\frac{μ _{0} I}{4 πr} (2 + π)$ (3) $\frac{μ _{0} I}{2 πr} (2 + π)$ (4) $\frac{μ _{0} I}{2 πr} (2 - π)$ 283. $Four identical long solenoids A, B, C and D are connected to each other as shown in the figure. If themagnetic field at the center of A is 3 T the field at the center of C would be : (Assume that the magnetic fieldis confined with in the volume of respective solenoid).$ (1) $12 T$ (2) $6 T$ (3) $9 T$ (4) $1 T$ 284. $A long, straight wire of radius a carries a current distributed uniformly over its cross-section. The ratio of the magnetic fields due to the wire at distance \frac{a}{3} and 2 a, respectively from the axis of the wire is :$ (1) $\frac{3}{5}$ (2) $\frac{2}{3}$ (3) $\frac{1}{2}$ (4) $\frac{4}{3}$ 285. $A wire carrying current l is bent in the shape ABCDEFA as shown, where rectangle ABCDA and ADEFA are perpendicular to each other. If the sides of the rectangles are of lengths a and b, then the magnitude and direction of magnetic moment of the loop ABCDEFA is$ (1) $abl, along (\frac{j ^}{5} + \frac{2 k ^}{5})$ (2) $2 abl, along (\frac{j ^}{2} + \frac{k ^}{2})$ (3) $abl, along (\frac{j ^}{2} + \frac{k ^}{2})$ (4) $2 abl, along (\frac{j ^}{5} + \frac{2 k ^}{5})$ 286. $The region between y = 0 and y = d contains a magnetic field B = B z . A particle of mass m and charge q enters the regionwith a velocity v = v i . if d = \frac{mv}{2 qB} the acceleration of thecharged particle at the point of its emergence at the other side is:$ (1) $\frac{qvB}{m} (\frac{1}{2} i - \frac{3}{2} j)$ (2) $\frac{qvB}{m} (\frac{3}{2} i + \frac{1}{2} j)$ (3) $\frac{qvB}{m} (\frac{- j + i}{2})$ (4) $\frac{qVB}{m} (\frac{- 3 i - j}{2})$ 287. $The torque required to hold a small circular coil of 10 turns, area 1 mm^{2} and carrying a current of (\frac{21}{44}) A in the middle of a long solenoid of 10^{3} turns/m carrying a current of 2.5 A, with its axis perpendicular to the axis of the solenoid is$ (1) $1.5 \times 10^{- 6} N m$ (2) $1.5 \times 10^{- 8} N m$ (3) $1.5 \times 10^{+ 6} N m$ (4) $1.5 \times 10^{+ 8} N m$ 288. $The magnitude of the force vector acting on a unit length of a thin wire carrying a current I = 8 A at a point O, if the wire is bent as shown in the figure with a radius, R = 10 πcm is$ (1) $64 μN / m$ (2) $32 μN / m$ (3) $20 μN / m$ (4) $100 μN / m$ 289. $A particle of charge q, mass m and kinetic energy E enters in magnetic field perpendicular to its velocity and undergoes a circular arc of radius (r) . Which of the following curves represents the variation of r with E ?$ (1) (2) (3) (4) 290. $A charged particle is subjected to acceleration in a cyclotron as shown. The charged particle undergoes increase in its speed$ (1) $only in the gap between D_{1} and D_{2}$ (2) $only inside D_{2}$ (3) $inside D_{1}, D_{2} and the gaps$ (4) $only inside D_{1}$ 291. $Two long parallel wires are at a distance 2d apart. They carry steady equal currents flowing out of the plane of the paper as shown. The variation of magnetic field B along the line XX´ is given by$ (1) (2) (3) (4) 292. $An infinitely long straight wire carrying current I is bent in a planer shape as shown in the diagram. The radius of the circular part is r . The magnetic field at the center O of the circular loop is:$ (1) $- \frac{μ _{0}}{2 π} \frac{I}{r} (π - 1) i$ (2) $\frac{μ _{0}}{2 π} \frac{I}{r} (π - 1) i$ (3) $- \frac{μ _{0}}{2 π} \frac{I}{r} (π + 1) i$ (4) $\frac{μ _{0}}{2 π} \frac{I}{r} (π + 1) i$ 293. $The magnetic field at center, P will be$ (1) $\frac{μ _{0}}{4 π}$ (2) $\frac{μ _{0}}{π}$ (3) $\frac{μ _{0}}{2 π}$ (4) $4 μ_{0} π$ 294. $The magnitude of the magnetic field at the center of an equilateral triangular loop of side 1 m which is carrying a current of 10 A is: [ Take μ_{o} = 4 π \times 10^{- 7} NA^{- 2}]$ (1) $18 μT$ (2) $9 μT$ (3) $3 μT$ (4) $1 μT$ 295. $The magnitude of magnetic induction at mid-point O due to current arrangement as shown in Fig will be:$ (1) $\frac{μ _{0} I}{2 πa}$ (2) $0$ (3) $\frac{μ _{0} I}{4 πa}$ (4) $\frac{μ _{0} I}{πa}$ 296. $A metallic rod of mass per unit length 0.5 kg m^{- 1} is lying horizontally on a smooth inclined plane which makes an angle of 30^{\circ} with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction 0.25 T is acting on it in the vertical direction. The current flowing in the rod to keep it stationary is [NEET 2018]$ (1) $14.76 A$ (2) $5.98 A$ (3) $7.14 A$ (4) $11.32 A$ 297. $To convert a galvanometer into a voltmeter one should connect a$ (1) $high resistance in series with galvanometer$ (2) $low resistance in series with galvanometer$ (3) $high resistance in parallel with galvanometer$ (4) $low resistance in parallel with galvanometer.$ 298. $A current carrying closed loop in the form of a right angle isosceles triangle ABC is placed in a uniform magnetic field acting along AB . If the magnetic force on the arm BC is F the force on the arm AC is$ (1) $- 2 F$ (2) $- F$ (3) $F$ (4) $2 F$ 299. $An element Δ l = Δ x i is placed at the origin and carries a large current I = 10 A . The magnetic field on the y -axis at a distance of 0.5 m from the elements Δ x of 1 cm length is:$ (1) $4 \times 10^{- 8} T$ (2) $10 \times 10^{- 8} T$ (3) $8 \times 10^{- 8} T$ (4) $12 \times 10^{- 8} T$ 300. $A galvanometer of resistance 240Ω allows only 4 % of the main current after connecting a shunt resistance. The value of the shunt resistance is$ (1) $10Ω$ (2) $20Ω$ (3) $8Ω$ (4) $5Ω .$