Moving Charges & Magnetism PYQs Set 1 (PDF)

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Mere Teacher · Previous Year Questions NEET Physics · Moving Charges & Magnetism · Set 1 (Q1-30)
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1. $A galvanometer of resistance 50Ω gives a full scale deflection for a current 5 \times 10^{- 4} A . The resistance that should be connected in series with the galvanometer to read 3 V is$ (1) $5050Ω$ (2) $5950Ω$ (3) $595Ω$ (4) $5059Ω$ 2. $A long solenoid has 200 turns per cm and carriers a current i . The magnetic field at its centre is 6.28 \times 10^{- 2} Wb / m^{2} . Another long solenoid has 100 turns per cm and it carries a current i /3 . The value of magnetic field at its center is nearly$ (1) $1.05 \times 10^{- 3} Wb / m^{2}$ (2) $1.05 \times 10^{- 5} Wb / m^{2}$ (3) $1.05 \times 10^{- 4} Wb / m^{2}$ (4) $1.05 \times 10^{- 2} Wb / m^{2}$ 3. $A long cylindrical wire of radius R carries a uniform current I flowing through it. The variation of magnetic field with distance r from the axis of the wire is shown by$ (1) (2) (3) (4) 4. $The electric current in a circular coil of 2 turns produces a magnetic induction B_{1} at its center. The coil is unwound and is rewound into a circular coil of 5 turns and the same current produces a magnetic induction B_{2} at its center. The ratio of \frac{B _{2}}{B _{1}} is:$ (1) $\frac{5}{2}$ (2) $\frac{25}{4}$ (3) $\frac{5}{4}$ (4) $\frac{25}{2}$ 5. $A proton, an electron, and a Helium nucleus, have the same energy. They are in circular orbits in a plane due to magnetic field perpendicular to the plane. Let r_{p}, r_{e} and r_{He} be their respective radii, then,$ (1) $r_{e} > r_{p} = r_{He}$ (2) $r_{e} < r_{p} = r_{He}$ (3) $r_{e} < r_{p} < r_{He}$ (4) $r_{e} > r_{p} > r_{He}$ 6. $A closely wound solenoid of 80 cm long has 5 layers of windings of 400 turns each. The diameter of the solenoid is 1.8 cm . If the current carried is 8 A, then the magnitude of the magnetic field inside the solenoid near its centre is approximately$ (1) $1.5 \times 10^{- 2} T$ (2) $2.5 \times 10^{- 2} T$ (3) $3.5 \times 10^{- 2} T$ (4) $4.5 \times 10^{- 2} T$ 7. $A tightly wound 100 turns coil of radius 10 cm carries a current of 7 A. The magnitude of the magnetic field at the center of the coil is (Take, permeability of free space as 4 π \times 10^{- 7} SI units) [NEET 2024]$ (1) $44 MT$ (2) $4.4 T$ (3) $4.4 mT$ (4) $44 T$ 8. $A current carrying solenoid is placed vertically and a particle of mass m with charge Q is released from rest. The particle moves along the axis of solenoid. If g is acceleration due to gravity then the acceleration$ (1) $of the charged particle will satisfy:(a) a > g$ (2) $0 < a < g$ (3) $a = 0$ (4) $a = g$ 9. $A voltmeter of 250 mV range having a resistance of 10Ω is converted into an ammeter of 250 mA range. The value of necessary shunt is (nearly)$ (1) $2Ω$ (2) $0.1Ω$ (3) $1Ω$ (4) $10Ω$ 10. $A beam of electrons is moving with constant velocity in a region having electric and magnetic fields of strength 20 V m^{- 1} and 0.5 T at right angles to the direction of motion of the electrons. What is the velocity of the electrons?$ (1) $8 m s^{- 1}$ (2) $5.5 m s^{- 1}$ (3) $20 m s^{- 1}$ (4) $40 m s^{- 1}$ 11. $10 A current is flowing in two straight parallel wires in the same direction. Force of attraction between them is 1 \times 10^{- 3} N . If the current is doubled in both the wires the force will be$ (1) $1 \times 10^{- 3} N$ (2) $2 \times 10^{- 3} N$ (3) $4 \times 10^{- 3} N$ (4) $0.25 \times 10^{- 3} N$ 12. $A long current carrying wire produces a magnetic field of 1 T at a distance of r . The magnetic field (i) \frac{r}{2} (ii) 2 r and (ii) 3 r is$ (1) $(i) 2T, (ii) = \frac{1}{2} T, (iii) = \frac{1}{3} T$ (2) $(i) 3 T, (ii) = \frac{1}{3} T, (iii) = \frac{1}{6} T$ (3) $(i) 3 2 T,(ii)=14T,(iii)=18T$ (4) $(i) \frac{5}{2} T, (ii) = \frac{1}{2} T, (iii) = \frac{1}{3} T$ 13. $A circular coil carrying a certain current produces a magnetic field B_{0} at its centre. The coil is now rewound so as to have 3 turns and the same current is passed through it. The new magnetic field at the centre is$ (1) $B_{0} /9$ (2) $9 B_{0}$ (3) $B_{0} /3$ (4) $3 B_{0}$ 14. $A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron$ (1) $will turn towards right of direction of motion$ (2) $speed will decrease$ (3) $speed will increase$ (4) $will turn towards left of direction of motion.$ 15. $A long straight wire of circular cross-section (radius a) is carrying steady current I. The current I is uniformly distributed across this cross-section. The magnetic field is$ (1) $inversely proportional to r in the region r < a and uniform throughout in the region r > a$ (2) $directly proportional to r in the region r < a and inversely proportional to r in the region r > a$ (3) $Zero in the region r < a and inversely proportional to r in the region r > a$ (4) $uniform in the region r < a and inversely proportional to distance r from the axis, in the region r > a$ 16. $A beam of protons with speed 4 \times 10^{5} ms^{- 1} enters a uniform magnetic field of 0.3 T at an angle of 60^{\circ} to the magnetic field. The pitch of the resulting helical path of protons is close to (Mass of the proton = 1.67 \times 10^{- 27} kg charge of the proton = 1.69 \times 10^{- 19} C)$ (1) $2 cm$ (2) $12 cm$ (3) $5 cm$ (4) $4 cm$ 17. $A magnetic field of 5 \times 10^{- 5} T is produced at a perpendicular distance of 0.2 m from a long straight wire carrying electric current. If the permeability of free space is 4 π \times 10^{- 7} Tm / A . The current passing through the wire in A is:$ (1) $45$ (2) $40$ (3) $50$ (4) $30$ 18. $Astraightwireofdiameter0.5mmcarrying a current of 1 A is replaced by the another wire of 1 mm diameter carrying the same current. The strength of the magnetic field far away is$ (1) $one‐quarter of the earlier value$ (2) $one‐half of the earlier value$ (3) $twice the earlier value$ (4) $same as the earlier value.$ 19. $A circular loop of radius r is carrying current I A. The ratio of magnetic field at the center of circular loop and at a distance r from the center of the loop on its axis is:$ (1) $1 : 3 2$ (2) $32 : 2$ (3) $22 : 1$ (4) $1 : 2$ 20. $Ionized hydrogen atoms and α ‐particles with same momenta enters perpendicular to a constant magnetic field, B . The ratio of their radii of their paths r_{H} : r_{α} will be$ (1) $1 : 4$ (2) $2: 1$ (3) $1 : 2$ (4) $4: 1$ 21. $A charged particle carrying charge 1 μC is moving with velocity (2 i + 3 j + 4 k) m s^{- 1} . If an external magnetic field of (5 i + 3 j - 6 k) \times 10^{- 3} T exists in the region where the particle is moving, then the force on the particle is F \times 10^{- 9} N . The vector F is$ (1) $- 0.30 i + 0.32 j - 0.09 k$ (2) $- 30 i + 32 j - 9 k$ (3) $- 300 i + 320 j - 90 k$ (4) $- 3.0 i + 3.2 j - 0.9 k$ 22. $The electric current in a circular coil of 2 turns produces a magnetic induction B_{1} at its centre. The coil is unwound and is rewound into a circular coil of 5 turns and the same current produces a magnetic induction B_{2} at its centre. The ratio of \frac{B _{2}}{B _{1}}$ (1) $\frac{5}{2}$ (2) $\frac{25}{4}$ (3) $\frac{5}{4}$ (4) $\frac{25}{2}$ 23. $For parallel conductors and steady currents, the results in accordance with Newton's third law are$ (1) $Biot-Savart law and the Lorentz force$ (2) $Biot-Savart law and Ampere's law$ (3) $Ampere's law and the Lorentz force$ (4) $Lenz's law and Lorentz force$ 24. $The magnetic field at the center of a current carrying loop of radius 0.1 m is 55 times that at a point along its axis. The distance of this point from the center of the loop is$ (1) $0.2 m$ (2) $0.05 m$ (3) $0.1 m$ (4) $0.25 m$ 25. $The magnetic field at a distance r from a long wire carrying current i is 0.4 tesla. The magnetic field at a distance 2 r is$ (1) $0.2 tesla$ (2) $0.8 tesla$ (3) $0.1 tesla$ (4) $1.6 tesla.$ 26. $An electron is moving in a circular path under the influence of a transverse magnetic field of 3.57 \times 10^{- 2} T . If the value of e / m is 1.76 \times 10^{11} C / kg, the frequency of revolution of the electron is [NEET 2016]$ (1) $1 GHz$ (2) $100 MHz$ (3) $62.8 MHz$ (4) $6.28 MHz$ 27. $For a moving coil galvanometer, the deflection in the coil is 0.05 rad when a current of 10 mA is passed through it. If the torsional constant of suspension wire is 4.0 x 1 0^{- 5} Nm r a d^{- 1}, the magnetic field is 0.01 T and the number of turns in the coil is 200, the area of each turn (in c m^{2}) is:$ (1) $2.0$ (2) $1.0$ (3) $1.5$ (4) $0.5$ 28. $If M_{0} and L_{0} denote the magnetic moment and angular momentum of the electron due to its orbital motion respectively, then the gyromagnetic ratio is given by$ (1) $\frac{L _{0}}{M _{0}}$ (2) $L_{0} M_{0}$ (3) $\frac{M _{0}}{L _{0}}$ (4) $\frac{M _{0}}{L _{0}}$ 29. $A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of magnetic field will be equal to$ (1) $B$ (2) $2 B$ (3) $4 B$ (4) $\frac{B}{2}$ 30. $Two long straight wires P and Q carrying equal current 10A each were kept parallel to each other at 5 cm distance. Magnitude of magnetic force experienced by 10 cm length of wire P is F_{1} . If distance between wires is halved and currents on them are doubled, force F_{2} on 10 cm length of wire P will be:$ (1) $8 F_{1}$ (2) $10 F_{1}$ (3) $F_{1} /8$ (4) $F_{1} /10$