33 Years NEET-AIPMT Chapterwise Solutions - Physics 2020

Moving Charges and Magnetism
Telegram @unacademyplusdiscounts
43
(a) a net attractive force towards the conductor
(b) a net repulsive force away from the conductor
(c) a net torque acting upward perpendicular to the
horizontal plane
(d) a net torque acting downward normal to the
horizontal plane. (Mains 2011)
58. Two long parallel wires are at a distance of 1 metre.
Both of them carry one ampere of current. The force
of attraction per unit length between the two wires is
(a) 5 × 10 –8 N/m (b) 2 × 10 –8 N/m
(c) 2 × 10 –7 N/m (d) 10 –7 N/m (1998)
59. Two parallel wires in free space are 10 cm apart and each
carries a current of 10 A in the same direction. The force
exerted by one wire on the other, per metre length is
(a) 2 × 10 –4 N, repulsive
(b) 2 × 10 –7 N, repulsive
(c) 2 × 10 –4 N, attractive
(d) 2 × 10 –7 N, attractive. (1997)
4.10 Torque on Current Loop, Magnetic Dipole
60. 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 Weber/m 2 . The coil carries
a current of 2 A. If the plane of the coil is inclined at an
angle of 30° with the direction of the field, the torque
required to keep the coil in stable equilibrium will be
(a) 0.24 N m (b) 0.12 N m
(c) 0.15 N m (d) 0.20 N m (2015)
61. A current loop in a magnetic field
(a) can be in equilibrium in two orientations, both
the equilibrium states are unstable.
(b) can be in equilibrium in two orientations, one
stable while the other is unstable.
(c) experiences a torque whether the field is uniform
or non uniform in all orientations.
(d) can be in equilibrium in one orientation.
(NEET 2013)
62. A circular coil ABCD carrying
a current ‘i’ is placed in a
uniform magnetic field. If the
magnetic force on the segment
AB is F, the force on the
remaining segment BCDA is
(a) −F (b) 3F (c) −3F
(d) F
(Karnataka NEET 2013)
63. A current carrying closed 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
(a) − 2F (b) −F
(c) F (d) 2F (2011)
64. A square current carrying loop is suspended in a
uniform magnetic field acting in the plane of the
loop. If the force on one arm of the loop is F the net
force on the remaining three arms of the loop is
(a) 3 F (b) − F (c) −3 F (d) F (2010)
65. A closed loop PQRS carrying
a current is placed in a
uniform magnetic field. If
the magnetic forces on
segments PS, SR and RQ are
F 1 , F 2 and F 3 respectively and
are in the plane of the paper
and along the directions
shown, the force on the
segment QP is
(a) ( F3 −F1)
2 − F2 2 (b) F 3 – F 1 + F 2
(c) F 3 – F 1 – F 2 (d) ( F3 − F1) 2 + F2 2 . (2008)
66. A charged particle (charge q) is moving in a circle
of radius R with uniform speed v. The associated
magnetic moment m is given by
(a) qvR 2 (b) qvR 2 /2 (c) qvR (d) qvR/2 (2007)
67. A coil in the shape of an equilateral triangle of side l
is suspended between the pole pieces of a permanent
magnet such that B is in plane of the coil. If due to a
current i in the triangle a torque t acts on it, the side
l of the triangle is
(a)
12 /
2 ⎛ τ ⎞
3 ⎝
⎜
Bi ⎠
⎟ (b) ⎛ τ ⎞
2
⎝
⎜
3Bi
⎠
⎟
(c)
12 /
2 ⎛ τ ⎞
1 τ
3 ⎝
⎜
Bi ⎠
⎟ (d)
3 Bi (2005)
68. If number of turns, area and current through a coil
is given by n, A and i respectively then its magnetic
moment will be
(a) niA (b) n 2 iA (c) niA 2 (d)
ni
. (2001)
A
69. A circular loop of area 0.01 m 2 carrying a current
of 10 A, is held perpendicular to a magnetic field of
intensity 0.1 T. The torque acting on the loop is
(a) 0.001 N m (b) 0.8 N m
(c) zero (d) 0.01 N m. (1994)
70. A coil carrying electric current is placed in uniform
magnetic field
(a) torque is formed
(b) e.m.f is induced
(c) both (a) and (b) are correct
(d) none of these (1993)
71. A current carrying coil is subjected to a uniform
magnetic field. The coil will orient so that its plane
becomes