Moving Charges & Magnetism PYQs Set 6 (PDF)

Set 6 of 17 · Questions 151-180 of 499

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Mere Teacher · Previous Year Questions NEET Physics · Moving Charges & Magnetism · Set 6 (Q151-180)
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151. $A proton moving with a velocity 2.5 \times 10^{7} m / s, enters a magnetic field of intensity 2.5 T making an angle 30^{\circ} with the magnetic field. The force on the proton is$ (1) $3 \times 10^{- 12} N$ (2) $5 \times 10^{- 12} N$ (3) $6 \times 10^{- 12} N$ (4) $9 \times 10^{- 12} N$ 152. $An electron is constrained to move along the y -axis with a speed of 0.1 c (c is the speed of light) in the presence of electromagnetic wave, whose electric field is E \to= 30 j^sin (1.5 \times 10^{7} t - 5 \times 10^{- 2} \times) V / m The maximum magnetic force experienced by the electron will be (given c = 3 \times 10^{8} ms^{- 1} and electron charge = 1.6 \times 10^{- 19} C)$ (1) $4.8 \times 10^{- 19} N$ (2) $2.4 \times 10^{- 18} N$ (3) $3.2 \times 10^{- 18} N$ (4) $1.6 \times 10^{- 19} N$ 153. $Two particles X and Y having equal charges are being accelerated through the same potential difference. Thereafter they enter normally in a region of uniform magnetic field and describes circular paths of radii R_{1} and R_{2} respectively. The mass ratio of X and Y is:$ (1) $(\frac{R _{2}}{R _{1}})^{2}$ (2) $(\frac{R _{1}}{R _{2}})^{2}$ (3) $(\frac{R _{1}}{R _{2}})$ (4) $(\frac{R _{2}}{R _{1}})$ 154. $Proton, Deuteron and alpha particle of same kinetic energy are moving in circular trajectories in a constant magnetic field. The radii of proton, deuteron and alpha particle are respectively r_{p}, r_{d} and r_{α} . Which one of the following relation is correct?$ (1) $r_{α} = r_{p} = r_{d}$ (2) $r_{α} = r_{p} < r_{d}$ (3) $r_{α} > r_{d} > r_{p}$ (4) $r_{α} = r_{d} > r_{p}$ 155. $Assertion (A): When proton and a neutron enter into a transverse magnetic field with equal speeds, then they trace a circular paths of equal radii. Reason (R): In a transverse magnetic field the period of revolution of a charged particle in a circular path is directly proportional to the mass of the particle.$ (1) $Both (A) and (R) are correct and (R) is the correct explanation of (A) .$ (2) $Both (A) and (R) are correct but (R) is not the correct explanation of (A) .$ (3) $(A) is correct but (R) is not correct.$ (4) $(A) is not correct but (R) is correct.$ 156. $A long wire carrying a steady current is bent into a circular loop of one turn. The magnetic field at the center of the loop is B . It is then bent into a circular coil of n turns. The magnetic field at the centre of this coil of n turns will be$ (1) $nB$ (2) $n^{2} B$ (3) $2 nB$ (4) $2 n^{2} B .$ 157. $A loop of flexible wire of irregular shape carrying current is placed in an external magnetic field. Identify the effect of the field on the wire.$ (1) $Loop assumes circular shape with its plane normal to the field.$ (2) $Loop assumes circular shape with its plane parallel to the field.$ (3) $Wire gets stretched to become straight.$ (4) $Shape of the loop remains unchanged.$ 158. $A circular coil of radius 10 cm and 100 turns carries a current 1 A . What is the magnetic moment of the coil ?$ (1) $3.142 A m^{2}$ (2) $3.142 \times 10^{4} A m^{2}$ (3) $3 A m^{2}$ (4) $10^{4} A m^{2}$ 159. $Two circular coils P and Q are made of two identical wires of the same length. The number of turns in the P and Q are 4 and 2, respectively. The magnetic inductions at the centre of P and Q are BP and BQ, respectively. The ratio \frac{B _{P}}{B _{Q}} is$ (1) $0.25$ (2) $4$ (3) $0.5$ (4) $2$ 160. $Choose the wrong statement to complete: An ideal solenoid has$ (1) $the turns widely separated.$ (2) $the turns closely wound.$ (3) $the length is very much greater than the radius.$ (4) $the magnetic field inside almost uniform.$ 161. $A wire loop of irregular shape carrying current is placed in an external magnetic field. If the wire is flexible, the shape of the loop changes to$ (1) $helical$ (2) $circular$ (3) $straight line$ (4) $parabolic$ 162. $Two to roads 1 and 2 have total number of turns 200 and 100 respectively with average radii 40 cm and 20 cm respectively. If they carry same current i, the radio of the magnetic fields along the two loops is$ (1) $1 : 1$ (2) $4 : 1$ (3) $2 : 1$ (4) $1 : 2$ 163. $The magnetic dipole moment of a current loop is independent of$ (1) $magnetic field in which it is lying$ (2) $number of turns$ (3) $area of the loop$ (4) $current in the loop.$ 164. $A toroid has an iron core with an Internal Magnetic field of 10 πmT, when the current in the winding of 1500 turns per metre is 10 A . Determine the field due to magnetisation (μ_{0} = 4 π \times 10^{- 7} Hm^{- 1})$ (1) $(4 π) mT$ (2) $(10 π) mT$ (3) $(\frac{8}{π}) mT$ (4) $(\frac{π}{4}) mT$ 165. $A bar magnet having a magnetic moment of 2.0 x 1 0^{5} J T^{- 1}, is placed along the direction of uniform magnetic field of magnitude B= 14 x 1 0^{- 5} T. The work done in rotating the magnet slowly through 60° from the direction of field is:$ (1) $14J$ (2) $8.4J$ (3) $4J$ (4) $1.4J$ 166. $A current i flows in an infinitely long, straight and thin walled pipe, then$ (1) $the magnetic field at all the points inside the pipe is same, but not zero$ (2) $the magnetic field at any point inside the pipe is zero$ (3) $the magnetic field is zero only on the axis of the pipe$ (4) $the magnetic field is different at different points inside the pipe$ 167. $Sensitivity of moving coil galvanometer is s. If a shunt of (\frac{1}{8})^{th} of the resistance of galvanometer is connected to moving coil galvanometer, its sensitivity becomes$ (1) $\frac{s}{3}$ (2) $\frac{s}{6}$ (3) $\frac{s}{9}$ (4) $\frac{5}{12}$ 168. $To convert a galvanometer into a ammeter, one needs to connect a$ (1) $low resistance in parallel$ (2) $high resistance in parallel$ (3) $low resistance in series$ (4) $high resistance in series$ 169. $The magnetic induction at a point P which is at the distance of 4 cm from a long current carrying wire is 1 0^{- 3} T. The field of induction at a distance 12 cm from the current will be$ (1) $3.33 \times 1 0^{- 4} T$ (2) $1.11 \times 1 0^{- 4} T$ (3) $33 \times 1 0^{- 3} T$ (4) $9 \times 1 0^{- 3} T$ 170. $A galvanometer of resistance 40Ω gives a deflection of 10 divisions per mA . There are 50 divisions on the scale. Maximum current that can pass through it when a shunt resistance of 2Ω is connected is$ (1) $105 mA$ (2) $155 mA$ (3) $210 mA$ (4) $75 mA$ 171. $A charged particle moves along circular path in a uniform magnetic field in a cyclotron. The kinetic energy of the charged particle increases to 4 times its initial value. What will be the ratio of new radius to the original radius of circular path of the charged particle:$ (1) $1 : 1$ (2) $1 : 2$ (3) $2 : 1$ (4) $1 : 4$ 172. $A closely wound solenoid of length 1 m has 5 layers of 500 turns each. If the magnitude of magnetic field inside the solenoid near its center is 4.4 mT, the current carried is$ (1) $1.4 A$ (2) $1.5 A$ (3) $1.6 A$ (4) $1.8 A$ 173. $The dipole moment of a circular loop carrying a current I, is m and the magnetic field at the centre of the loop is B_{1} . When the dipole moment is doubled by keeping the current constant, the magnetic field at the centre of loop is B_{2} . The ratio \frac{B _{1}}{B _{2}} is:$ (1) $2$ (2) $\frac{1}{2}$ (3) $2$ (4) $3$ 174. $The time taken for the magnetic energy to reach 25 % of its maximum value, when a solenoid of resistance R,inductance L is connected to a battery, is:$ (1) $\frac{L}{R} l n 5$ (2) $infinite$ (3) $\frac{L}{R} l n 2$ (4) $\frac{L}{R} l n 10$ 175. $A charged particle (charge q) is moving in a circle of radius R with uniform speed v . The associated magnetic moment μ is given by$ (1) $qv R^{2}$ (2) $qv R^{2} /2$ (3) $qvR$ (4) $qvR /2$ 176. $The torque acting on a magnetic dipole placed in uniform magnetic field is zero, when the angle between the dipole axis and the magnetic field is$ (1) $zero$ (2) $45^{\circ}$ (3) $60^{\circ}$ (4) $90^{\circ}$ 177. $Ionized hydrogen atoms and α-particle with momenta enters perpendicular to a constant magnetic field, B. The ratio of their radii of their paths r_{H} : r_{α} will be:$ (1) $1 ; 4$ (2) $2 : 1$ (3) $1 : 2$ (4) $4 : 1$ 178. $There are four light-weight-rod samples A, B, C, D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted: (i) A is feebly repelled (ii) B is feebly attracted (iii) C is strongly attracted (iv) D remains unaffected Which one of the following is true?$ (1) $B is of a paramagnetic material$ (2) $C is of a diamagnetic material$ (3) $D is of a ferromagnetic material$ (4) $A is of a non-magnetic material$ 179. $A circular coil of 10 turns and radius 10 cm is placed in a uniform magnetic field of 0.1 T normal to the plane of the coil. If the current in the coil is 5 A, then the magnitude of the torque on the coil is$ (1) $500 πN - m$ (2) $0.05 πN - m$ (3) $0.005 πN - m$ (4) $zero$ 180. $An electron having mass m and kinetic energy E enter in uniform magnetic field B perpendicularly, then its frequency will be$ (1) $\frac{eE}{qvB}$ (2) $\frac{2 πm}{eB}$ (3) $\frac{eB}{2 πm}$ (4) $\frac{2 m}{eBE}$