Moving Charges & Magnetism PYQs Set 13 (PDF)

Set 13 of 17 · Questions 361-390 of 499

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Mere Teacher · Previous Year Questions NEET Physics · Moving Charges & Magnetism · Set 13 (Q361-390)
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361. $A uniform electric field E = (8m/e) V/m is created between two parallel plates of length 1m as shown in figure, (where m = mass of electron and e = charge of electron). An electron enters the field symmetrically between the plates with a speed of 2m/s. The angle of the deviation (θ) of the path of the electron as it comes out of the field will be _______$ (1) $t a n^{- 1} (4)$ (2) $t a n^{- 1} (2)$ (3) $t a n^{- 1} (\frac{1}{3})$ (4) $t a n^{- 1} (3)$ 362. $The magnetic induction at point O of the given infinitely long current carrying wire shown in the figure below is$ (1) $\frac{μ _{0} l}{4 πR} (1 - \frac{3 π}{2})$ (2) $\frac{μ _{0} l}{2 R ( 1 + π )}$ (3) $\frac{μ _{0} l}{4 πR} (1 + \frac{3 π}{2})$ (4) $\frac{μ _{0} l}{4 πR}$ 363. $A thin circular disk of radius R is uniformly charged with density σ > 0 per unit area. The disk rotates about its axis with a uniform angular speed ω . The magnetic moment of the disk is:$ (1) $π R^{4} σω$ (2) $\frac{π R ^{4}}{2} σω$ (3) $\frac{π R ^{4}}{4} σω$ (4) $2 π R^{4} σω$ 364. $A positively charged particle of mass m is passed through a velocity selector. It moves horizontally rightward without deviation along the line y = \frac{2 mv}{qB} with a speed v . The electric field is vertically downward and magnetic field is into the plane of the paper. Now, the electric field is switched off at t = 0 . The angular momentum of the charged particle about the origin O at t = \frac{πm}{qB} is$ (1) $\frac{m E ^{2}}{q B ^{3}}$ (2) $\frac{2 m E ^{2}}{q B ^{3}}$ (3) $zero$ (4) $\frac{4 m ^{2} E ^{2}}{q B ^{3}}$ 365. $Figure shows a current carrying square loop ABCD of edge length is ' a' lying in a plane. If the resistance of the ABC part is r and that of ADC part is 2 r, then the magnitude of the resultant magnetic field at centre of the square loop is$ (1) $\frac{2 μ _{0} I}{3 πa}$ (2) $\frac{2 μ _{0} I}{3 πa}$ (3) $\frac{3 π μ _{0} I}{2 a}$ (4) $\frac{μ _{0} I}{2 πa}$ 366. $There are two infinitely long straight current carrying conductors and they are held at right angles to each other so that their common ends meet at the origin as shown in the figure given below. The ratio of current in both conductor is 1:1. The magnetic field at point P is$ (1) $\frac{μ _{0} I}{4 πxy} (x^{2} + y^{2} + (x + y))$ (2) $\frac{μ _{0} I}{4 πxy} (x^{2} + y^{2} - (x + y))$ (3) $\frac{μ _{0} Ixy}{4 π} (x^{2} + y^{2} - (x + y))$ (4) $\frac{μ _{0} Ixy}{4 π} (x^{2} + y^{2} + (x + y))$ 367. $Two wires A & B are carrying currents I_{1} and I_{2} as shown in the figure. The separation between them is d . A third wire C carrying a current I is to be kept parallel to them at a distance x from A such that the net force acting on it is zero. The possible values of x are:$ (1) $x = (\frac{I _{1}}{I _{1} - I _{2}}) d and x = \frac{I _{2}}{( I _{1} + I _{2} )} d$ (2) $x = (\frac{I _{2}}{( I _{1} + I _{2} )}) d and x = (\frac{I _{2}}{( I _{1} - I _{2} )}) d$ (3) $x = (\frac{I _{1}}{( I _{1} + I _{2} )}) d and x = (\frac{I _{2}}{( I _{1} - I _{2} )}) d$ (4) $x = \pm \frac{I _{1} d}{( I _{1} - I _{2} )}$ 368. $At a point A on the earth’s surface of angle of dip, d = +25º. At a point B on the earth’s surface the angle of dip, d = -25º. We can interpret that:$ (1) $A and B are both located in the southern hemisphere.$ (2) $A and B are both located in the northern hemisphere.$ (3) $A is located in the southern hemisphere and B is located in the northern hemisphere.$ (4) $A is located in the northern hemisphere and B is located in the southern hemisphere.$ 369. $A long straight wire carries a certain current and produces a magnetic field 2 \times 1 0^{- 4} Wb m^{- 2} at a perpendicular distance of 5 cm from the wire. An electron situated at 5 cm from the wire moves with a velocity 1 0^{7} m / s towards the wire along perpendicular to it. The force experienced by the electron will be (charge on electron 1.6 \times 1 0^{- 19} C)$ (1) $3.2 N$ (2) $3.2 \times 1 0^{- 16} N$ (3) $1.6 \times 1 0^{- 16} N$ (4) $zero.$ 370. $What is the value of shunt resistance required to convert a galvanometer of resistance 100Ω into an ammeter of range 1 A ? Given: Full scale deflection of the galvanometer is 5 mA .$ (1) $0.5Ω$ (2) $\frac{5}{9.95} Ω$ (3) $0.05Ω$ (4) $\frac{9.95}{5} Ω$ 371. $A rectangular coil of length 0.12 m and width 0.1 m having 50 turns of wire is suspended vertically in a uniform magnetic field of strength 0.2 Wb / m^{2} . The coil carries a current of 2 A. If the plane of the coil is inclined at an angle of 30^{\circ} with the direction of the field. the torque required to keep the coil in stable equilibrium will be$ (1) $0.15 N - m$ (2) $0.20 N - m$ (3) $0.24 N - m$ (4) $0.12 N - m$ 372. $Two long parallel straight metal wires A and B carrying currents 12 A and 36 A respectively, in the same direction are separated by 50 cm . The point relative to A, where the resultant magnetic induction between the two wires due to the currents is zero, will be$ (1) $90 cm$ (2) $7.5 cm$ (3) $28 cm$ (4) $12.5 cm$ 373. $A long straight wire carrying a current of 25 A rests on the table. Another wire PQ of length 1 m and mass 2.5 g carries the same current but in the opposite direction. The wire PQ is free to slide up and down. To what height will wire PQ rise? (μ_{0} = 4 π \times 10^{- 7} SI unit)$ (1) $3 mm$ (2) $4 mm$ (3) $5 mm$ (4) $8 mm$ 374. $Three parallel wires a, b and c carrying currents i_{a}, i_{b} and i_{c} as shown in the figure are placed next to each other. The magnitude force on a length l of the wire a, if d_{2} = 2 d_{1}, i_{b} = i_{a} and i_{c} = 4 i_{a} is$ (1) $\frac{μ _{0}}{6 π d _{1}} i_{a}^{2} l$ (2) $\frac{μ _{0}}{2 π d _{1}} i_{a}^{2} l$ (3) $\frac{μ _{0}}{4 π d _{1}} i_{a}^{2} l$ (4) $\frac{μ _{0}}{3 π d _{1}} i_{a}^{2} l$ 375. $A current I a flows in a circular arc of radius r subtending an angle θ as shown in the figure. Find the magnetic field at the centre O of the circle.$ (1) $\frac{μ _{0} Iθ}{4 πr}$ (2) $\frac{2 μ _{0} I \cdot sin θ}{4 πr}$ (3) $\frac{2 μ _{0} Isin θ}{2 r}$ (4) $\frac{2 μ _{0} Isin θ}{4 r}$ 376. $An iron bar of length l has magnetic moment M. It is bent at the middle of its length such that the two arms make an angle 60^{\circ} with each other. The magnetic moment of this new magnet is [NEET 2024]$ (1) $M$ (2) $\frac{M}{2}$ (3) $2M$ (4) $\frac{M}{3}$ 377. $Two tangent galvanometers A and B are identical except in their number of turns. They are connected in series. On passing a current through them, deflections of 60^{\circ} and 30^{\circ} are produced. The ratio of the number of turns in A and B is$ (1) $1 : 2$ (2) $2 : 1$ (3) $1 : 3$ (4) $3 : 1$ 378. $The figure gives experimentally measured B vs. H variation in a ferromagnetic material. The retentivity co-ercivity and saturation, respectively, of the material are :$ (1) $50 A / m, 1 T, 1.5 T$ (2) $1.5 T, 50 A / m, 1 T$ (3) $1 T, 50 A / m, 1.5 T$ (4) $50 A / m, 1.5 T, 1 T$ 379. $A very long wire carrying a current 42 A is bent at a right angles. The magnitude of magnetic field (\| B \|) at a point P lying on a line perpendicular to the bent wire at a distance, d = 20 cm from the point of the bending will be (Let μ_{0} = 4 π \times 10^{- 7} H / m)$ (1) $1 μT$ (2) $0.8 μT$ (3) $2 μT$ (4) $4 μT$ 380. $ABCD is a rectangular loop made of uniform wire. If AD = BC = 2 cm, what is the magnetic force per unit length acting on wire DC due to wire AB, if ammeter reads 20 A ? (The length of AB and DC are large in comparison with other two sides)$ (1) $10^{- 1} Nm^{- 1}$ (2) $10^{- 2} Nm^{- 1}$ (3) $10^{- 3} Nm^{- 1}$ (4) $10^{- 4} Nm^{- 1}$ 381. $An electron moves in a circular orbit with a uniform speed v . It produces a magnetic field B at the centre of the circle. The radius of the circle is proportional to$ (1) $B / v$ (2) $B / v$ (3) $v / B$ (4) $vlB$ 382. $Two thick wires and two thin wires, all of same material and same length, form a square in three different ways P, Q and R as shown in the figure. With correct connections shown, the magnetic field due to the current flow, at the centre of the loop will be zero in case of$ (1) $Q and R only$ (2) $P and Q only$ (3) $P only$ (4) $P and R only$ 383. $A coil having N turns is wound tightly in the form of a spiral with inner and outer radii 'a' and 'b' respectively. Find the magnetic field at center, when a current I passes through coil:$ (1) $\frac{μ _{0} IN}{2 ( b - a )} log_{e} (\frac{b}{a})$ (2) $\frac{μ _{0} I}{8} (\frac{a + b}{a - b})$ (3) $\frac{μ _{0} I}{4 ( a - b )} (\frac{1}{a} - \frac{1}{b})$ (4) $\frac{μ _{0} I}{8} (\frac{a - b}{a + b})$ 384. $Find the magnetic field at the point P in figure. The curved portion is a semicircle connected to two long straight wires.$ (1) $\frac{μ _{0} i}{2 r} (1 + \frac{2}{π})$ (2) $\frac{μ _{0} i}{2 r} (1 + \frac{1}{π})$ (3) $\frac{μ _{0} i}{2 r} (\frac{1}{2} + \frac{1}{2 π})$ (4) $\frac{μ _{0} i}{2 r} (\frac{1}{2} + \frac{1}{π})$ 385. $A current carrying loop in the form of a right angle isosceles triangle ABC is placed in a uniform magnetic field acting along AB. If the magnetic force on the arm BC is F, the force on the arm AC is:$ (1) $- 2 F$ (2) $- F$ (3) $F$ (4) $2 F$ 386. $Two long current carrying conductors are placed parallel to each other at a distance of 8 cm between them. The magnitude of magnetic field produced at mid-point between the two conductors due to current flowing in them is 300µT. The equal current flowing in the two conductors is:$ (1) $30A in the same direction.$ (2) $30A in the opposite direction.$ (3) $60A in the opposite direction.$ (4) $300A in the opposite direction.$ 387. $A straight wire of length 50 cm carrying a current of 2.5 A is suspended in mid-air by a uniform magnetic field of 0.5 T (as shown in figure). The mass of the wire is (g = 10 m s^{- 2})$ (1) $100 gm$ (2) $125 gm$ (3) $62.5 gm$ (4) $250 gm$ 388. $If only \frac{1}{51}^{th} of the main current is to be passed through a galvanometer then the shunt required is R_{1} and if only \frac{1 ^{th}}{11} of the main voltage is to be developed across the galvanometer, then the resistance required R_{2} . Then \frac{R _{2}}{R _{1}}$ (1) $\frac{1}{. 500}$ (2) $\frac{50}{9}$ (3) $\frac{500}{3}$ (4) $500$ 389. $Two long parallel wires are separated by a distance of 2.5 cm . The force per unit length that each wire exerts on the other is 4 \times 10^{- 5} N / m and the wires repel each other. The current in one wire is 0.5 A . What is the current in the second wire? (Take μ_{0} = 4 π \times 10^{- 7} SI unit)$ (1) $12 A$ (2) $8 A$ (3) $6 A$ (4) $10 A$ 390. $A direct current I flows along the length of an infinitely long straight thin walled pipe, then the magnetic field is$ (1) $uniform throughout the pipe but not zero$ (2) $zero only along the axis of the pipe$ (3) $zero at any point inside the pipe$ (4) $maximum at the centre and minimum at the edges.$