Tiêu đề 04. MOVING CHARGES AND MAGNETISM (1).pdf ✅

E⃗ should be perpendicular to the direction of velocity Which one of the following pairs of statements is possible? (a) (1) and (3) (b) (3) and (4) (c) (2) and (3) (d) (2) and (4) (Mains 2010) 28. A beam of electron passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move (a) in a circular orbit (b) along a parabolic path (c) along a straight line (d) in an elliptical orbit. (2007) 29. In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular paths of radius R using a magnetic field B. If V and B are kept constant, the ratio ( charge on the ion mass of the ion ) will be proportional to (a) 1/R 2 (b) R 2 (c) R (d) 1/R (2007) 30. In Thomson mass spectrograph E⃗ ⊥ B⃗ then the velocity of electron beam will be (a) |E⃗ | |B⃗ | (b) E⃗ × B⃗ (c) |B⃗ | |E⃗ | (d) E 2 B2 (2001) 31. 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? (a) 8 m s −1 (b) 5.5 m s −1 (c) 20 m s −1 (d) 40 m s −1 (1996) 4.4 Magnetic Field due to a Current Element, Biot-Savart Law 32. Given below are two statements : Statement I : Biot-Savart's law gives us the expression for the magnetic field strength of an infinitesimal current element (Idl) of a current carrying conductor only. Statement II : Biot-Savart's law is analogous to Coulomb's inverse square law of charge q, with the former being related to the field produced by a scalar source, Idl while the latter being produced by a vector source, q. In light of above statements choose the most appropriate answer from the options given below. (a) Both Statement I and Statement II are correct. (b) Both Statement I and Statement II are incorrect. (c) Statement I is correct and Statement II is incorrect. (d) Statement I is incorrect and Statement II is correct. (2022) 33. The magnetic field dB⃗ due to a small current element dl at a distance r and element carrying current i is (a) dB⃗ = μ0 4π i 2 ( dl ×r r ) (b) dB⃗ = μ0 4π i ( dl ×r r 3 ) (c) dB⃗ = μ0 4π i ( dl ×r r ) (d) dB⃗ = μ0 4π i 2 ( dl ×r r 2 ) (1996) 4.5 Magnetic Field on the Axis of a Circular Current Loop 34. Averylong conducting wire is bent in a semi- circular shape from A to B as shown in figure. The magnetic field at point P for steady current