Moving Charges & Magnetism PYQs Set 8 (PDF)

Set 8 of 19 · Questions 211-240 of 549

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Mere Teacher · Previous Year Questions JEE Main Physics · Moving Charges & Magnetism · Set 8 (Q211-240)
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211. $Magnetic field due to 0.1 A current flowing through a circular coil of radius 0.1 m and 1000 turns at the centre of the coil is$ (1) $6.28 \times 1 0^{- 4} T$ (2) $4.31 \times 1 0^{- 2} T$ (3) $2 \times 1 0^{- 1} T$ (4) $9.81\times 1 0^{- 4} T.$ 212. $A wire is first bent in the form of a circular coil of 5 turns and the same wire is then bent in the form of another circular coil of 10 turns. If same current is passed in both the coils, then the ratio of the magnetic fields at their centers is$ (1) $1 : 8$ (2) $1 : 1$ (3) $1 : 2$ (4) $1 : 4$ 213. $A coil is placed in a time varying magnetic field. If the number of turns in the coil were to be halved and the radius of wire doubled, the electrical power dissipated due to the current induced in the coil would be: (Assume the coil to be short circuited.)$ (1) $Halved$ (2) $Quadrupled$ (3) $The same$ (4) $Doubled$ 214. $A tightly wound long solenoid has n turns per unit length, a radius r and carries a current I . A particle having charge q and mass m is projected from a point on the axis in a direction perpendicular to the axis. The maximum speed of the particle for which the particle does not strike the solenoid is$ (1) $\frac{μ _{0} nIqr}{m}$ (2) $\frac{μ _{0} nIqr}{2 m}$ (3) $\frac{μ _{0} nIqr}{4 m}$ (4) $\frac{μ _{0} nIqr}{8 m}$ 215. $Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R . Assertion A : When a rod lying freely is heated, no thermal stress is developed in it. Reason R : On heating, the length of the rod increases. In the light of the above statements, choose the correct answer from the options given below:$ (1) $A is true but R is false$ (2) $Both A and R are true and R is the correct explanation of A$ (3) $Both A and R are true but R is NOT the correct explanation of A$ (4) $A is false but R is true$ 216. $A proton moves with velocity of 5 \times 10^{6} j m s^{- 1} through the uniform electric field E = 4 \times 10^{6} [2 i + 0.2 j + 0.1 k] Vm^{- 1} and the uniform magnetic field B = 0.2 [i + 0.2 j + k] T . The approximate net force acting on the proton is$ (1) $2.2 \times 10^{- 13} N$ (2) $5 \times 10^{- 13} N$ (3) $20 \times 10^{- 13} N$ (4) $14.48 \times 10^{- 13} N$ 217. $A proton, a deuteron and an α -particle are projected perpendicular to the direction of a uniform magnetic field with same kinetic energy. The ratio of the radii of the circular paths described by them is$ (1) $1 : 2 : 2$ (2) $1 : 2 : 1$ (3) $2 : 2 : 1$ (4) $2 : 1 : 1$ 218. $Consider a long straight wire of a circular cross-section (radius a) carrying a steady current I. The current is uniformly distributed across this cross-section. The distances from the center of the wire's cross-section at which the magnetic field [inside the wire, outside the wire] is half of the maximum possible magnetic field, anywhere due to the wire, will be$ (1) $[a /4, 3 a /2]$ (2) $[a /4, 2 a]$ (3) $[a /2, 2 a]$ (4) $[a /2, 3 a]$ 219. $A particle having the same charge as of electron moves in a circular path of radius 0.5 cm under the influence of magnetic field of 0.5 T. If an electric field of 100 V/m makes it to move in a straight path, then the mass of the particle is (Given charge of electron = 1.6 \times 1 0^{-19} C)$ (1) $2.0 \times 1 0^{-24} kg$ (2) $1.6 \times 1 0^{-27} kg$ (3) $9.1 \times 1 0^{-31} kg$ (4) $1.6 \times 1 0^{-19} kg$ 220. $The magnetic field at the center of a circular coil of radius r, due to current I flowing through it, is B. The magnetic field at a point along the axis at a distance \frac{r}{2} from the center is:$ (1) $B/2$ (2) $2B$ (3) $(\frac{2}{5})^{3} B$ (4) $(\frac{2}{3})^{3} B$ 221. $A charged particle moves through a magnetic field perpendicular to its direction. Then,$ (1) $kinetic energy changes but the momentum is constant$ (2) $the momentum changes but the kinetic energy is constant$ (3) $both momentum and kinetic energy of the particles are not constant$ (4) $both momentum and kinetic energy of the particles are constant$ 222. $A paramagnetic material has 1 0^{28} atoms/ m^{3} . Its magnetic susceptibility at temperature 350 K is 2.8 \times 1 0^{-4} . Its susceptibility at 300 K is:$ (1) $3.726 \times 1 0^{-4}$ (2) $3.672 \times 1 0^{-4}$ (3) $3.267 \times 1 0^{-4}$ (4) $2.672 \times 1 0^{-4}$ 223. $A long straight wire of radius a carries a steady current I . The current is uniformly distributed across its cross section. The ratio of the magnetic field at \frac{a}{2} and 2 a from axis of the wire is :$ (1) $1 : 4$ (2) $1 : 1$ (3) $3 : 4$ (4) $4 : 1$ 224. $A charged particle (charge = q; mass = m) is rotating in a circle of radius R with uniform speed V . Ratio of its magnetic moment (μ) to the angular momentum (L) is$ (1) $\frac{q}{2 m}$ (2) $\frac{q}{m}$ (3) $\frac{q}{4 m}$ (4) $\frac{2 q}{m}$ 225. $A wire carrying a current I along the positive X-axis has length L. It is kept in a magnetic field B = (2 i + 3 j - 4 k) T . The magnitude of the magnetic force acting on the wire is. [NEET 2023]$ (1) $5 IL$ (2) $5 IL$ (3) $3 IL$ (4) $3 IL$ 226. $B_{x} and B_{Y} are the magnetic field at the center of two coils of two coils X and Y respectively, each carrying equal current. If coil X has 200 turns and 20 cm radius and coil Y has 400 turns and 20 cm radius, the ratio of B_{x} and B_{Y} is$ (1) $1 : 1$ (2) $1 : 2$ (3) $2 : 1$ (4) $4 : 1$ 227. $Given below are two statements: Statement I: If the number of turns in the coil of a moving coil galvanometer is doubled then the current sensitivity becomes double. Statement II: Increasing current sensitivity of a moving coil galvanometer by only increasing the number of turns in the coil will also increase its voltage sensitivity in the same ratio In the light of the above statements, choose the correct answer from the options given below:$ (1) $Statement I is true but Statement II is false$ (2) $Statement I is false but Statement II is true$ (3) $Both Statement I and Statement II are false$ (4) $Both Statement I and Statement II are true$ 228. $A coil of one turn is made of a wire of certain length and then from the same length a coil of two turns is made. If the same current is passed in both the cases, then the ratio of the magnetic inductions at their centers will be$ (1) $4 : 1$ (2) $1 : 4$ (3) $2 : 1$ (4) $1 : 2$ 229. $If ' q' is electric charge, B is magnetic field, ' R' is the dee radius and ' m' is the mass of ions, the kinetic energy of the ions in cyclotron is given by$ (1) $\frac{qBR}{2 m}$ (2) $\frac{qBR}{m}$ (3) $\frac{q ^{2} B ^{2} R ^{2}}{4 πm}$ (4) $\frac{q ^{2} B ^{2} R ^{2}}{2 m}$ 230. $The magnetic field at the centre of a circular current carrying conductor of radius r is B_{c} . The magnetic field on its axis at a distance r from the centre is B_{a} . The value of B_{c} : B_{a} will be$ (1) $22 : 1$ (2) $2 : 1$ (3) $1 : 2$ (4) $1 : 22$ 231. $A proton carrying 1 MeV kinetic energy is moving in a circular path of radius R in uniform magnetic field. What should be the energy of an α - particle to describe a circle of same radius in the same field?$ (1) $2 MeV$ (2) $1 MeV$ (3) $0.5 MeV$ (4) $4 MeV$ 232. $A plane electromagnetic wave is propagating along the direction \frac{i ^ + j ^}{2} with its polarization along the direction k^. The correct from of the magnetic field of the wave would be (here B_{0} is an appropriate constant):$ (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) $B_{0} k^cos (ωt - k \frac{i ^ + j ^}{2})$ 233. $A charged particle experiences magnetic force in the presence of magnetic field. Which of the following statement is correct?$ (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) $The particle is moving and magnetic field is parallel to velocity.$ 234. $A toroid has 500 turns per metre length. If it carries a current of 2 A, the magnetic energy density inside the toroid is$ (1) $6.28 J m^{- 3}$ (2) $0.628 J m^{- 3}$ (3) $3.14 J m^{- 3}$ (4) $0.314 J m^{- 3}$ 235. $A particle of mass m and charge q is moving in a cyclotron with magnetic field B . The frequency of the circular motion of the particle is proportional to$ (1) $\frac{qB}{m}$ (2) $\frac{2 m}{qB}$ (3) $\frac{mB}{q}$ (4) $\frac{mq}{B}$ 236. $A circular coil of 30 turns and radius 8 cm carrying a current of 6 A is suspended vertically in a uniform horizontal magnetic field of magnitude 1.0 T . The field lines make an angle of 30^{\circ} with the normal of the coil. The magnitude of the counter torque that must be applied to prevent the coil from turning is$ (1) $5.4 Nm$ (2) $7.2 Nm$ (3) $3.6 Nm$ (4) $1.8 Nm$ 237. $The current amplification factor and the collector current in a CE transistor circuit are 100 and 2.2 mA respectively. Then the base current is$ (1) $0.22 μA$ (2) $22 μA$ (3) $220 μA$ (4) $2.2 μA$ 238. $A charge Q is moving dI distance in the magnetic field B . Find the value of work done by B .$ (1) $1$ (2) $Infinite$ (3) $Zero$ (4) $- 1$ 239. $A uniform conducting wire of length is 24a, and resistance R is wound up as a current carrying coil in the shape of an equilateral triangle of side 'a' and then in the form of a square of side 'a'. The coil is connected to a voltage source V_{0} . The ratio of magnetic moment of the coils in case of equilateral triangle to that for square is 1 : y where y is$ 240. $An electron in a hydrogen atom revolves around its nucleus with a speed of 6. 76 x 106 m s^{- 1} in an orbit of radius 0.52 A 0 . The magnetic field produced at the nucleus of the hydrogen atom is_______T.$