Moving Charges & Magnetism PYQs Set 7 (PDF)

Set 7 of 17 · Questions 181-210 of 499

In the print window choose “Save as PDF”. The file prints without a web address or date line.

Mere Teacher · Previous Year Questions NEET Physics · Moving Charges & Magnetism · Set 7 (Q181-210)
Scan or visit mereteacher.com for free PYQ practice, timed CBT tests, step-by-step solutions and BroBot AI. Answers and solutions are free with a sign-up.
181. $A toroid has a non ferromagnetic core of inner radius 24 cm and outer radius 25 cm, around which 4900 turns of a wire are wound. If the current in the wire is 12 A, the magnetic field inside the core of the toroid is$ (1) $56 mT$ (2) $54 mT$ (3) $42 mT$ (4) $48 mT$ 182. $A wire of length L metre carrying a current I ampere is bent in the form of a circle. Magnitude of its magnetic moment is$ (1) $\frac{L ^{2} I ^{2}}{4 π}$ (2) $\frac{L ^{2} I}{4 π}$ (3) $\frac{LI}{4 π}$ (4) $\frac{L I ^{2}}{4 π}$ 183. $A long conducting wire having a current I flowing through it, is bent into a circular coil of N turns. Then it is bent into a circular coil of n turns. The magnetic field is calculated at the center of coils in both the cases. The ratio of the magnetic field in first case to that of second case is:$ (1) $N : n$ (2) $n2 : N2$ (3) $N^{2} : n^{2}$ (4) $n : N$ 184. $A steel wire of length 1 and magnetic moment M is bent into a semicircular arc of radius R . The new magnetic moment is$ (1) $M$ (2) $\frac{2 RM}{πl}$ (3) $\frac{2 M}{π}$ (4) $\frac{2 πRM}{l}$ 185. $The ratio of magnetic field at the centre of a current carrying circular coil to its magnetic moment is x . If the current and the radius both are doubled. The new ratio will become$ (1) $x /4$ (2) $x /8$ (3) $2 x$ (4) $4 x$ 186. $A thin magnetic needle is placed in a magnetic field of 200 G with its axis at 30^{\circ} to the direction of the field. Find the magnetic moment of the needle if it experiences a torque of 0.012 Nm in this field.$ (1) $1.2 Am^{2}$ (2) $12.0 Am^{2}$ (3) $0.6 Am^{2}$ (4) $6.0 Am^{2}$ 187. $A charged particle when enters a uniform magnetic field moves in a helical path. If its angular velocity is 4 π \times 10^{6} rads^{- 1} and its velocity in the direction of magnetic field is 3 \times 10^{5} ms^{- 1} then the pitch of the helix is$ (1) $5 cm$ (2) $10 cm$ (3) $15 cm$ (4) $20 cm$ 188. $The magnetic field at the origin due to a current element \| dl \| placed at a point with vector position r is$ (1) $\frac{μ _{0} i}{4 π} \frac{dl \times r}{r ^{2}}$ (2) $\frac{μ _{0} i}{4 π} \frac{r \times dl}{r}$ (3) $\frac{μ _{0} i}{4 π} \frac{dl \times r}{r ^{3}}$ (4) $\frac{μ _{0} i}{4 π} \frac{r \times dl}{r ^{3}}$ 189. $A proton and helium nucleus are shot into a magnetic field at right angles to the field with same kinetic energy. Then the ratio of their radii is$ (1) $1 : 1$ (2) $1 : 2$ (3) $2 : 1$ (4) $1 : 4$ 190. $The coercivity of a small magnet where the ferromagnet gets demagnetized is 3 \times 1 0^{3} A m^{-1} . The current required to be passed in a solenoid of length 20 cm and number of turns 100, so that the magnetic gets demagnetized when inside the solenoid, is:$ (1) $30 mA$ (2) $60 mA$ (3) $3 A$ (4) $6 A$ 191. $A galvanometer having a coil of resistance 60 Ω shows full scale deflection when a current of 1.0 amp passes through it. It can be converted into an ammeter to read currents upto 5.0 amp by$ (1) $putting in series a resistance of 15 Ω$ (2) $putting in series a resistance of 240 Ω$ (3) $putting in parallel a resistance of 15 Ω$ (4) $putting in parallel a resistance of 240 Ω .$ 192. $Magnetic field due to 0.1 A current flowing through a circular coil of radius 0.1 m and 1000 turns at the centre of the coil is$ (1) $6.28 \times 1 0^{- 4} T$ (2) $4.31 \times 1 0^{- 2} T$ (3) $2 \times 1 0^{- 1} T$ (4) $9.81\times 1 0^{- 4} T.$ 193. $A wire is first bent in the form of a circular coil of 5 turns and the same wire is then bent in the form of another circular coil of 10 turns. If same current is passed in both the coils, then the ratio of the magnetic fields at their centers is$ (1) $1 : 8$ (2) $1 : 1$ (3) $1 : 2$ (4) $1 : 4$ 194. $A coil is placed in a time varying magnetic field. If the number of turns in the coil were to be halved and the radius of wire doubled, the electrical power dissipated due to the current induced in the coil would be: (Assume the coil to be short circuited.)$ (1) $Halved$ (2) $Quadrupled$ (3) $The same$ (4) $Doubled$ 195. $A tightly wound long solenoid has n turns per unit length, a radius r and carries a current I . A particle having charge q and mass m is projected from a point on the axis in a direction perpendicular to the axis. The maximum speed of the particle for which the particle does not strike the solenoid is$ (1) $\frac{μ _{0} nIqr}{m}$ (2) $\frac{μ _{0} nIqr}{2 m}$ (3) $\frac{μ _{0} nIqr}{4 m}$ (4) $\frac{μ _{0} nIqr}{8 m}$ 196. $Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R . Assertion A : When a rod lying freely is heated, no thermal stress is developed in it. Reason R : On heating, the length of the rod increases. In the light of the above statements, choose the correct answer from the options given below:$ (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) $A is false but R is true$ 197. $A proton moves with velocity of 5 \times 10^{6} j m s^{- 1} through the uniform electric field E = 4 \times 10^{6} [2 i + 0.2 j + 0.1 k] Vm^{- 1} and the uniform magnetic field B = 0.2 [i + 0.2 j + k] T . The approximate net force acting on the proton is$ (1) $2.2 \times 10^{- 13} N$ (2) $5 \times 10^{- 13} N$ (3) $20 \times 10^{- 13} N$ (4) $14.48 \times 10^{- 13} N$ 198. $A proton, a deuteron and an α -particle are projected perpendicular to the direction of a uniform magnetic field with same kinetic energy. The ratio of the radii of the circular paths described by them is$ (1) $1 : 2 : 2$ (2) $1 : 2 : 1$ (3) $2 : 2 : 1$ (4) $2 : 1 : 1$ 199. $Consider a long straight wire of a circular cross-section (radius a) carrying a steady current I. The current is uniformly distributed across this cross-section. The distances from the center of the wire's cross-section at which the magnetic field [inside the wire, outside the wire] is half of the maximum possible magnetic field, anywhere due to the wire, will be$ (1) $[a /4, 3 a /2]$ (2) $[a /4, 2 a]$ (3) $[a /2, 2 a]$ (4) $[a /2, 3 a]$ 200. $A particle having the same charge as of electron moves in a circular path of radius 0.5 cm under the influence of magnetic field of 0.5 T. If an electric field of 100 V/m makes it to move in a straight path, then the mass of the particle is (Given charge of electron = 1.6 \times 1 0^{-19} C)$ (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) $1.6 \times 1 0^{-19} kg$ 201. $The magnetic field at the center of a circular coil of radius r, due to current I flowing through it, is B. The magnetic field at a point along the axis at a distance \frac{r}{2} from the center is:$ (1) $B/2$ (2) $2B$ (3) $(\frac{2}{5})^{3} B$ (4) $(\frac{2}{3})^{3} B$ 202. $A charged particle moves through a magnetic field perpendicular to its direction. Then,$ (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) $both momentum and kinetic energy of the particles are constant$ 203. $A paramagnetic material has 1 0^{28} atoms/ m^{3} . Its magnetic susceptibility at temperature 350 K is 2.8 \times 1 0^{-4} . Its susceptibility at 300 K is:$ (1) $3.726 \times 1 0^{-4}$ (2) $3.672 \times 1 0^{-4}$ (3) $3.267 \times 1 0^{-4}$ (4) $2.672 \times 1 0^{-4}$ 204. $A long straight wire of radius a carries a steady current I . The current is uniformly distributed across its cross section. The ratio of the magnetic field at \frac{a}{2} and 2 a from axis of the wire is :$ (1) $1 : 4$ (2) $1 : 1$ (3) $3 : 4$ (4) $4 : 1$ 205. $A charged particle (charge = q; mass = m) is rotating in a circle of radius R with uniform speed V . Ratio of its magnetic moment (μ) to the angular momentum (L) is$ (1) $\frac{q}{2 m}$ (2) $\frac{q}{m}$ (3) $\frac{q}{4 m}$ (4) $\frac{2 q}{m}$ 206. $A wire carrying a current I along the positive X-axis has length L. It is kept in a magnetic field B = (2 i + 3 j - 4 k) T . The magnitude of the magnetic force acting on the wire is. [NEET 2023]$ (1) $5 IL$ (2) $5 IL$ (3) $3 IL$ (4) $3 IL$ 207. $B_{x} and B_{Y} are the magnetic field at the center of two coils of two coils X and Y respectively, each carrying equal current. If coil X has 200 turns and 20 cm radius and coil Y has 400 turns and 20 cm radius, the ratio of B_{x} and B_{Y} is$ (1) $1 : 1$ (2) $1 : 2$ (3) $2 : 1$ (4) $4 : 1$ 208. $Given below are two statements: Statement I: If the number of turns in the coil of a moving coil galvanometer is doubled then the current sensitivity becomes double. Statement II: Increasing current sensitivity of a moving coil galvanometer by only increasing the number of turns in the coil will also increase its voltage sensitivity in the same ratio In the light of the above statements, choose the correct answer from the options given below:$ (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) $Both Statement I and Statement II are true$ 209. $A coil of one turn is made of a wire of certain length and then from the same length a coil of two turns is made. If the same current is passed in both the cases, then the ratio of the magnetic inductions at their centers will be$ (1) $4 : 1$ (2) $1 : 4$ (3) $2 : 1$ (4) $1 : 2$ 210. $If ' q' is electric charge, B is magnetic field, ' R' is the dee radius and ' m' is the mass of ions, the kinetic energy of the ions in cyclotron is given by$ (1) $\frac{qBR}{2 m}$ (2) $\frac{qBR}{m}$ (3) $\frac{q ^{2} B ^{2} R ^{2}}{4 πm}$ (4) $\frac{q ^{2} B ^{2} R ^{2}}{2 m}$