Moving Charges & Magnetism PYQs Set 8 (PDF)

Set 8 of 17 · Questions 211-240 of 499

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Mere Teacher · Previous Year Questions NEET Physics · Moving Charges & Magnetism · Set 8 (Q211-240)
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211. $The magnetic field at the centre of a circular current carrying conductor of radius r is B_{c} . The magnetic field on its axis at a distance r from the centre is B_{a} . The value of B_{c} : B_{a} will be$ (1) $22 : 1$ (2) $2 : 1$ (3) $1 : 2$ (4) $1 : 22$ 212. $A proton carrying 1 MeV kinetic energy is moving in a circular path of radius R in uniform magnetic field. What should be the energy of an α - particle to describe a circle of same radius in the same field?$ (1) $2 MeV$ (2) $1 MeV$ (3) $0.5 MeV$ (4) $4 MeV$ 213. $A plane electromagnetic wave is propagating along the direction \frac{i ^ + j ^}{2} with its polarization along the direction k^. The correct from of the magnetic field of the wave would be (here B_{0} is an appropriate constant):$ (1) $B_{0} \frac{i ^ + j ^}{2} cos (ωt - k \frac{i ^ + j ^}{2})$ (2) $B_{0} \frac{i ^ - j ^}{2} cos (ωt + k \frac{i ^ + j ^}{2})$ (3) $B_{0} \frac{i ^ - j ^}{2} cos (ωt - k \frac{i ^ + j ^}{2})$ (4) $B_{0} k^cos (ωt - k \frac{i ^ + j ^}{2})$ 214. $A charged particle experiences magnetic force in the presence of magnetic field. Which of the following statement is correct?$ (1) $The particle is stationary and magnetic field is perpendicular:$ (2) $The particle is moving and magnetic field is perpendicular to the velocity.$ (3) $The particle is stationary and magnetic field is parallel.$ (4) $The particle is moving and magnetic field is parallel to velocity.$ 215. $A toroid has 500 turns per metre length. If it carries a current of 2 A, the magnetic energy density inside the toroid is$ (1) $6.28 J m^{- 3}$ (2) $0.628 J m^{- 3}$ (3) $3.14 J m^{- 3}$ (4) $0.314 J m^{- 3}$ 216. $A particle of mass m and charge q is moving in a cyclotron with magnetic field B . The frequency of the circular motion of the particle is proportional to$ (1) $\frac{qB}{m}$ (2) $\frac{2 m}{qB}$ (3) $\frac{mB}{q}$ (4) $\frac{mq}{B}$ 217. $A circular coil of 30 turns and radius 8 cm carrying a current of 6 A is suspended vertically in a uniform horizontal magnetic field of magnitude 1.0 T . The field lines make an angle of 30^{\circ} with the normal of the coil. The magnitude of the counter torque that must be applied to prevent the coil from turning is$ (1) $5.4 Nm$ (2) $7.2 Nm$ (3) $3.6 Nm$ (4) $1.8 Nm$ 218. $The current amplification factor and the collector current in a CE transistor circuit are 100 and 2.2 mA respectively. Then the base current is$ (1) $0.22 μA$ (2) $22 μA$ (3) $220 μA$ (4) $2.2 μA$ 219. $A charge Q is moving dI distance in the magnetic field B . Find the value of work done by B .$ (1) $1$ (2) $Infinite$ (3) $Zero$ (4) $- 1$ 220. $The fractional change in the magnetic field intensity at a distance 'r' from centre on the axis of current carrying coil of radius 'a' to the magnetic field intensity at the centre of the same coil is: (Take r < a)$ (1) $\frac{3}{2} \frac{a ^{2}}{r ^{2}}$ (2) $\frac{2}{3} \frac{a ^{2}}{r ^{2}}$ (3) $\frac{2}{3} \frac{r ^{2}}{a ^{2}}$ (4) $\frac{3}{2} \frac{r ^{2}}{a ^{2}}$ 221. $A proton beam enters a magnetic field of 10^{- 4} Wb m^{- 2} normally. If the specific charge of the proton is 10^{11} C kg^{- 1} and its velocity is 10^{9} m s^{- 1}, then the radius of the circle described will be$ (1) $10 m$ (2) $1 m$ (3) $0.1 m$ (4) $100 m$ 222. $A horizontal overhead powerline at a height of 5 m from the ground and carries a current of 150 A from East to West. The magnetic field directly below it on ground is$ (1) $6\times 1 0^{- 6} T, towards South$ (2) $6\times 1 0^{- 6} T, towards West$ (3) $7 \times 10^{- 6} T, towards East$ (4) $8 \times 10^{- 7} T, towards North$ 223. $A galvanometer of resistance 50Ω is connected to a battery of 3 V along with a resistance 2950Ω in series. A full deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 20 divisions, the resistance in series should be$ (1) $5050Ω$ (2) $6050Ω$ (3) $4450Ω$ (4) $5550Ω$ 224. $A toroid core has inner radius of 0.24 m and outer radius of 0.26 m . A current of 10 A flows through the wire having 2500 turns around it. Find the magnetic field inside the core of the toroid.$ (1) $π \times 10^{- 2} T$ (2) $2π\times 1 0^{- 2} T$ (3) $2 \times 10^{- 2} T$ (4) $20 \times 10^{- 2} T$ 225. $A positively charged particle moving due East enters a region of uniform magnetic field directed vertically upwards. This particle will$ (1) $move in a circular path with a decreased speed$ (2) $move in a circular path with a uniform speed$ (3) $get deflected in vertically upward direction$ (4) $move in circular path with an increased speed$ 226. $A charge moving with velocity v in X ‐direction is subjected to a field of magnetic induction in negative X ‐direction. As a result, the charge will$ (1) $remain unaffected$ (2) $start moving in a circular path Y‐Z plane$ (3) $retard along X ‐axis$ (4) $moving along a helical path around X ‐axis.$ 227. $To produce a magnetic field of π tesla at the centre of circular loop of diameter 1 m, the current flowing through loop is$ (1) $5 \times 10^{6} A$ (2) $10^{7} A$ (3) $2.5 \times 10^{6} A$ (4) $2 \times 10^{6} A$ 228. $In the cyclotron, as radius of the circular path of the charged particle increases (ω = angular velocity, v = linear velocity)$ (1) $both ω and v increases$ (2) $only ω increases, v remains constant$ (3) $v increases, ω remains constant$ (4) $v increases, ω decreases$ 229. $A long solenoid of 50 cm length having 100 turns carries a current of 2.5 A. The magnetic field at the center of solenoid is (Take, μ_{0} = 4 π \times 10^{- 7} Tm A^{- 1}) [NEET 2020]$ (1) $3.14 \times 10^{- 4} T$ (2) $6.28 \times 10^{- 5} T$ (3) $3.14 \times 10^{- 5} T$ (4) $6.28 \times 10^{- 4} T$ 230. $The distance moved by a charged particle along the magnetic field (the component of velocity is parallel to the magnetic field) in one rotation is given by (- mass of the particle, v - velocity of the particle, q charge of the particle, B - magnetic field)$ (1) $\frac{2 πmv}{qB}$ (2) $\frac{πmv}{qB}$ (3) $\frac{4 πmv}{qB}$ (4) $\frac{2 πmv}{qB ^{2}}$ 231. $A bar magnet having a magnetic moment of 2.0 \times 10^{5} JT^{- 1}, is placed along the direction of uniform magnetic field of magnitude B = 14 \times 10^{- 5} T . The work done in rotating the magnet slowly through 60^{\circ} from the direction of field is$ (1) $14 J$ (2) $8.4 J$ (3) $4 J$ (4) $1.4 J$ 232. $A proton and an alpha particle both enter a region of uniform magnetic field B, moving at right angles to the field B . If the radius of circular orbits for both the particles is equal and the kinetic energy acquired by proton is 1 MeV, the energy acquired by the alpha particle will be$ (1) $1.5 MeV$ (2) $1 MeV$ (3) $4 MeV$ (4) $0.5 MeV$ 233. $Two long straight parallel conductors 10 cm apart, carry equal currents of magnitude 3 A in the same direction. Then, the magnetic induction at a point midway between them is$ (1) $2 \times 10^{- 5} T$ (2) $3 \times 10^{- 5} T$ (3) $zero$ (4) $4 \times 10^{- 5} T$ 234. $Which of the field pattern given below is valid for electric field as well as for magnetic field?$ (1) (2) (3) (4) 235. $The magnetic force q [v \times B] is$ (1) $parallel to both v and B$ (2) $perpendicular to V$ (3) $perpendicular to both V and B$ (4) $parallel to B$ 236. $A wire of length l carries a current I along the X -axis. The magnetic force acting on the wire is given by F = IB_{0} l (k - j) T, where B 0 is a constant. The existing magnetic field B is$ (1) $B_{0} i$ (2) $B_{0} (i + j - k)$ (3) $B_{0} (i + j + k)$ (4) $B_{0} (i - j - k)$ 237. $A proton and an alpha particle of the same speed enter in a uniform magnetic field which is acting perpendicular to their direction of motion. The ratio of the circular paths described by the alpha particle and proton is:$ (1) $1 : 4$ (2) $4 : 1$ (3) $2 : 1$ (4) $1 : 2$ 238. $A closely wound solenoid of 2000 turns and area of cross‐section 1.5 \times 1 0^{- 4} m^{2} carries a current of 2.0 A. It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field 5 \times 1 0^{- 2} tesla making an angle of 3 0^{o} with the axis of the solenoid. The torque on the solenoid will be$ (1) $3 \times 1 0^{- 3} Nm$ (2) $1.5 \times 1 0^{- 3} Nm$ (3) $1.5 \times 1 0^{- 2} Nm$ (4) $3\times 1 0^{- 2} Nm.$ 239. $An electron, a proton and an alpha particle having the same kinetic energy are moving in circular orbits of radii r_{e}, r_{p}, r_{α} respectively in uniform magnetic field B. The relation between r_{e}, r_{p}, r_{α} is:$ (1) $r_{e} < r_{p} < r_{α}$ (2) $r_{e} < r_{α} < r_{p}$ (3) $re > rp = rα$ (4) $re < rp = rα$ 240. $A proton and an alpha-particle moving with the same velocity enter a uniform magnetic field with their velocities perpendicular to the magnetic field. The ratio of radii of their circular paths is$ (1) $2 : 1$ (2) $1 : 4$ (3) $4 : 1$ (4) $1 : 2$