Page 1
DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice questions.
Each question has 4 choices (a), (b), (c) and (d), out of which ONLY
ONE choice is correct.
Q.1 A circular coil has radius 4 cm and 20 number of turns
carries a current of 3 ampere. It is placed in a magnetic
field of intensity 0.5 weber/m
2
. The magnetic dipole
moment of the coil is
22
Take
7
æö
p=
ç÷
èø
(a) 0.15 ampere m
2
(b) 0.3 ampere m
2
(c) 0.45 ampere m
2
(d) 0.6 ampere m
2
Q.2 A circular coil of radius 4 cm has 50 turns. In this coil a
current of 2 A is flowing. It is placed in a magnetic field of
0.1 weber/m
2
. The amount of work done in rotating it
through 180° from its equilibrium position will be
(a) 0.1 J (b) 0.2 J (c) 0.4 J (d) 0.8 J
Q.3 The deflection in a moving coil galvanometer is
(a) directly proportional to the torsional constant
(b) directly proportional to the number of turns in the coil
(c) inversely proportional to the area of the coil
(d) inversely proportional to the current flowing
Q.4 A moving coil galvanometer has N number of turns in a
coil of effective area A. It carries a current I. The magnetic
field B is radial. The torque acting on the coil is
(a)
22
NA BI (b)
2
NABI
(c)
2
N ABI
(d)
NABI
Q.5 A current carrying loop is free to turn in a uniform magnetic
field. The loop will then come into equilibrium when its
plane is inclined at
(a) 0° to the direction of the field
(b) 45° to the direction of the field
(c) 90° to the direction of the field
(d) 135° to the direction of the field
Page 2
DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice questions.
Each question has 4 choices (a), (b), (c) and (d), out of which ONLY
ONE choice is correct.
Q.1 A circular coil has radius 4 cm and 20 number of turns
carries a current of 3 ampere. It is placed in a magnetic
field of intensity 0.5 weber/m
2
. The magnetic dipole
moment of the coil is
22
Take
7
æö
p=
ç÷
èø
(a) 0.15 ampere m
2
(b) 0.3 ampere m
2
(c) 0.45 ampere m
2
(d) 0.6 ampere m
2
Q.2 A circular coil of radius 4 cm has 50 turns. In this coil a
current of 2 A is flowing. It is placed in a magnetic field of
0.1 weber/m
2
. The amount of work done in rotating it
through 180° from its equilibrium position will be
(a) 0.1 J (b) 0.2 J (c) 0.4 J (d) 0.8 J
Q.3 The deflection in a moving coil galvanometer is
(a) directly proportional to the torsional constant
(b) directly proportional to the number of turns in the coil
(c) inversely proportional to the area of the coil
(d) inversely proportional to the current flowing
Q.4 A moving coil galvanometer has N number of turns in a
coil of effective area A. It carries a current I. The magnetic
field B is radial. The torque acting on the coil is
(a)
22
NA BI (b)
2
NABI
(c)
2
N ABI
(d)
NABI
Q.5 A current carrying loop is free to turn in a uniform magnetic
field. The loop will then come into equilibrium when its
plane is inclined at
(a) 0° to the direction of the field
(b) 45° to the direction of the field
(c) 90° to the direction of the field
(d) 135° to the direction of the field
2
DPP/ P 41
Q.6 A 100 turns coil shown in figure carries a current of 2 amp
in a magne tic fie ld B = 0.2Wb/m
2
. The torque acting on
the coil is
C
B A
D
10 cm
8 cm
N
S
(a) 0.32 Nm tending to rotate the side AD out of the page
(b) 0.32 Nm tending to rotate the side AD into the page
(c) 0.0032 Nm tending to rotate the side AD out of the
page
(d) 0.0032 Nm tending to rotate the side AD into the page
Q.7 A rectangular coil of size 20 cm × 20 cm has 100 turns
and carries a current of 1 A. It is placed in a uniform
magnetic field B = 0.5 T with the direction of magnetic
field parallel to the plane of the coil. The magnitude of the
torque required to hold this coil in this position is
(a) zero (b) 200 Nm
(c) 2 Nm (d) 10 Nm
Q.8 A circular loop of area 0.01m
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) zero (b) 0.01 Nm
(c) 0.001 N m (d) 0.8 Nm
Q.9 The magnetic moment of a current carrying circular coil is
(a) directly proportional to the length of the wire
(b) inversely proportional to the length of the wire
(c) directly proportional to the square of the length of
the wire
(d) inversely proportional to the square of the length of
the wire
Q.10 What is the shape of magnet in moving coil galvanometer
to make the radial magnetic field?
(a) Concave cylindrical (b) Horse shoe magnet
(c) Convex cylindrical (d) None of these
Q.11 Current i is carried in a wire of length L. If the wire is
turned into a circular coil, the maximum magnitude of
torque in a given magnetic field B will be
(a)
2
2
LiB
(b)
2
2
LiB
(c)
2
4
L iB
p
(d)
2
4
LiB
p
Q.12 In ballistic galvanometer, the frame on which the coil is
wound is non-metallic. It is
(a) to avoid the production of induced e.m.f.
(b) to avoid the production of eddy currents
(c) to increase the production of eddy currents
(d) to increase the production of induced e.m.f.
Q.13 A solenoid of length 0.4 m and having 500 turns of wire
carries a current of 3 amp. A thin coil having 10 turns of wire
and of radius 0.01 m carries a current of 0.4 amp. The torque
(in Nm) required to hold the coil in the middle of the solenoid
with its axis perpendicular to the axis of the solenoid is
(m
0
= 4p × 10
–7
V -s/A-m)
(a) 59.2 × 10
–6
(b) 5.92 × 10
–6
(c) 0.592 × 10
–6
(d) 0.592 × 10
–4
.
Q.14 If an electron is moving with velocity v in an orbit of radius
r in a hydrogen atom, then the equivalent magnetic moment is
(a)
0
µe
2r
(b)
2
ev
r
(c)
7
3
ev 10
r
,
´
(d)
evr
2
Q.15 In a moving coil galvanometer, the deflection of the coil q is
related to the electrical current i by the relation
(a) i µ tan q (b) i µ q
(c) i µ q
2
(d) iµq
Q.16 A thin circular wire carrying a current I has a magnetic
moment M. The shape of the wire is changed to a square
and it carries the same current. It will have a magnetic
moment
(a) M (b)
2
4
M
p
(c)
4
M
p
(d)
4
M
p
Q.17 A ring of radius R, made of an insulating material carries a
charge Q uniformly distributed on it. If the ring rotates about
the axis passing through its centre and normal to plane of
the ring with constant angular speed w, then the magnitude
of the magnetic moment of the ring is
(a)
2
QR w (b)
2
1
2
QR w (c)
2
QR w (d)
2
1
2
QR w
Page 3
DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice questions.
Each question has 4 choices (a), (b), (c) and (d), out of which ONLY
ONE choice is correct.
Q.1 A circular coil has radius 4 cm and 20 number of turns
carries a current of 3 ampere. It is placed in a magnetic
field of intensity 0.5 weber/m
2
. The magnetic dipole
moment of the coil is
22
Take
7
æö
p=
ç÷
èø
(a) 0.15 ampere m
2
(b) 0.3 ampere m
2
(c) 0.45 ampere m
2
(d) 0.6 ampere m
2
Q.2 A circular coil of radius 4 cm has 50 turns. In this coil a
current of 2 A is flowing. It is placed in a magnetic field of
0.1 weber/m
2
. The amount of work done in rotating it
through 180° from its equilibrium position will be
(a) 0.1 J (b) 0.2 J (c) 0.4 J (d) 0.8 J
Q.3 The deflection in a moving coil galvanometer is
(a) directly proportional to the torsional constant
(b) directly proportional to the number of turns in the coil
(c) inversely proportional to the area of the coil
(d) inversely proportional to the current flowing
Q.4 A moving coil galvanometer has N number of turns in a
coil of effective area A. It carries a current I. The magnetic
field B is radial. The torque acting on the coil is
(a)
22
NA BI (b)
2
NABI
(c)
2
N ABI
(d)
NABI
Q.5 A current carrying loop is free to turn in a uniform magnetic
field. The loop will then come into equilibrium when its
plane is inclined at
(a) 0° to the direction of the field
(b) 45° to the direction of the field
(c) 90° to the direction of the field
(d) 135° to the direction of the field
2
DPP/ P 41
Q.6 A 100 turns coil shown in figure carries a current of 2 amp
in a magne tic fie ld B = 0.2Wb/m
2
. The torque acting on
the coil is
C
B A
D
10 cm
8 cm
N
S
(a) 0.32 Nm tending to rotate the side AD out of the page
(b) 0.32 Nm tending to rotate the side AD into the page
(c) 0.0032 Nm tending to rotate the side AD out of the
page
(d) 0.0032 Nm tending to rotate the side AD into the page
Q.7 A rectangular coil of size 20 cm × 20 cm has 100 turns
and carries a current of 1 A. It is placed in a uniform
magnetic field B = 0.5 T with the direction of magnetic
field parallel to the plane of the coil. The magnitude of the
torque required to hold this coil in this position is
(a) zero (b) 200 Nm
(c) 2 Nm (d) 10 Nm
Q.8 A circular loop of area 0.01m
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) zero (b) 0.01 Nm
(c) 0.001 N m (d) 0.8 Nm
Q.9 The magnetic moment of a current carrying circular coil is
(a) directly proportional to the length of the wire
(b) inversely proportional to the length of the wire
(c) directly proportional to the square of the length of
the wire
(d) inversely proportional to the square of the length of
the wire
Q.10 What is the shape of magnet in moving coil galvanometer
to make the radial magnetic field?
(a) Concave cylindrical (b) Horse shoe magnet
(c) Convex cylindrical (d) None of these
Q.11 Current i is carried in a wire of length L. If the wire is
turned into a circular coil, the maximum magnitude of
torque in a given magnetic field B will be
(a)
2
2
LiB
(b)
2
2
LiB
(c)
2
4
L iB
p
(d)
2
4
LiB
p
Q.12 In ballistic galvanometer, the frame on which the coil is
wound is non-metallic. It is
(a) to avoid the production of induced e.m.f.
(b) to avoid the production of eddy currents
(c) to increase the production of eddy currents
(d) to increase the production of induced e.m.f.
Q.13 A solenoid of length 0.4 m and having 500 turns of wire
carries a current of 3 amp. A thin coil having 10 turns of wire
and of radius 0.01 m carries a current of 0.4 amp. The torque
(in Nm) required to hold the coil in the middle of the solenoid
with its axis perpendicular to the axis of the solenoid is
(m
0
= 4p × 10
–7
V -s/A-m)
(a) 59.2 × 10
–6
(b) 5.92 × 10
–6
(c) 0.592 × 10
–6
(d) 0.592 × 10
–4
.
Q.14 If an electron is moving with velocity v in an orbit of radius
r in a hydrogen atom, then the equivalent magnetic moment is
(a)
0
µe
2r
(b)
2
ev
r
(c)
7
3
ev 10
r
,
´
(d)
evr
2
Q.15 In a moving coil galvanometer, the deflection of the coil q is
related to the electrical current i by the relation
(a) i µ tan q (b) i µ q
(c) i µ q
2
(d) iµq
Q.16 A thin circular wire carrying a current I has a magnetic
moment M. The shape of the wire is changed to a square
and it carries the same current. It will have a magnetic
moment
(a) M (b)
2
4
M
p
(c)
4
M
p
(d)
4
M
p
Q.17 A ring of radius R, made of an insulating material carries a
charge Q uniformly distributed on it. If the ring rotates about
the axis passing through its centre and normal to plane of
the ring with constant angular speed w, then the magnitude
of the magnetic moment of the ring is
(a)
2
QR w (b)
2
1
2
QR w (c)
2
QR w (d)
2
1
2
QR w
DPP/ P 41
3
Q.18 The (t - q) graph for a current carrying coil placed in a
uniform magnetic field is
(a)
0°
180° 90°
q
(b)
0°
180° 90°
q
(c)
0°
180° 90°
q
(d)
0°
180° 90°
q
Q.19A rectangular loop carrying a current i is placed in a
uniform magnetic field B. The area enclosed by the loop
is A. If there are n turns in the loop, the torque acting on
the loop is given by
(a) niAB ´
r r
(b) ni A.B
r r
(c)
1
(i A B)
n
´
r r
(d)
1
(iA.B)
n
r r
Q.20The pole pieces of the magnet used in a pivoted coil
galvanometer are
(a) plane surfaces of a bar magnet
(b) plane surfaces of a horse-shoe magnet
(c) cylindrical surfaces of a bar magnet
(d) cylindrical surfaces of a horse-shoe magnet
DIRECTIONS (Q.21-Q.23) : In the following questions,
more than one of the answers given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.21 Four wires each of length 2.0 metre are bent into four loops
P, Q, R and S and then suspended into uniform magnetic
field. Same current is passed in each loop. Which
statements are incorrect?
P
Q R
S
(1) Couple on loop P will be the highest
(2) Couple on loop Q will be the highest
(3) Couple on loop R will be the highest
(4) Couple on loop S will be the highest
Q.22The sensitivity of a moving coil galvanometer can be
increased by
(1) decreasing the couple per unit twist of the suspension
(2) increasing the number of turns in the coil
(3) decreasing the area of the coil
(4) decreasing the magnetic field
Q.23A current carrying rectangular coil is placed in a uniform
magnetic field. In which orientation, the coil will tend to
rotate
(1) The magnetic field is parallel to the plane of the coil
(2) The magnetic field is at 45° with the plane of the coil
(3) In any orientation
(4) The magnetic field is perpendicular to the plane of
the coil
DIRECTIONS (Q.24-Q.26) : Read the passage given below
and answer the questions that follows :
A wire carrying a 10 A current is
bent to pass through sides of a cube
of side 10 cm as shown in figure. A
magnetic field
ˆ ˆˆ
B (2i 3j k)T = -+
r
is
present in the region. Then, find
2
y
z
4
x
1
3
Q.24 The net force on the loop
(a)
net
F0 =
r
(b)
net
ˆˆ
F (0.1i 0.2k)N =-
r
(c)
net
ˆˆ
F (0.3i 0.4k)N =+
r
(d)
net
ˆ
F (0.36k)N =
r
Q.25 The magnetic moment vector of the loop.
(a)
2
ˆ ˆˆ
(0.1i 0.05j 0.05k)Am +- (b)
2
ˆ ˆˆ
(0.1i 0.05j 0.05k)Am ++
(c)
2
ˆ ˆˆ
(0.1i 0.05j 0.05k)Am -+ (d)
2
ˆ ˆˆ
(0.1i 0.05j 0.05k)Am --
Page 4
DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice questions.
Each question has 4 choices (a), (b), (c) and (d), out of which ONLY
ONE choice is correct.
Q.1 A circular coil has radius 4 cm and 20 number of turns
carries a current of 3 ampere. It is placed in a magnetic
field of intensity 0.5 weber/m
2
. The magnetic dipole
moment of the coil is
22
Take
7
æö
p=
ç÷
èø
(a) 0.15 ampere m
2
(b) 0.3 ampere m
2
(c) 0.45 ampere m
2
(d) 0.6 ampere m
2
Q.2 A circular coil of radius 4 cm has 50 turns. In this coil a
current of 2 A is flowing. It is placed in a magnetic field of
0.1 weber/m
2
. The amount of work done in rotating it
through 180° from its equilibrium position will be
(a) 0.1 J (b) 0.2 J (c) 0.4 J (d) 0.8 J
Q.3 The deflection in a moving coil galvanometer is
(a) directly proportional to the torsional constant
(b) directly proportional to the number of turns in the coil
(c) inversely proportional to the area of the coil
(d) inversely proportional to the current flowing
Q.4 A moving coil galvanometer has N number of turns in a
coil of effective area A. It carries a current I. The magnetic
field B is radial. The torque acting on the coil is
(a)
22
NA BI (b)
2
NABI
(c)
2
N ABI
(d)
NABI
Q.5 A current carrying loop is free to turn in a uniform magnetic
field. The loop will then come into equilibrium when its
plane is inclined at
(a) 0° to the direction of the field
(b) 45° to the direction of the field
(c) 90° to the direction of the field
(d) 135° to the direction of the field
2
DPP/ P 41
Q.6 A 100 turns coil shown in figure carries a current of 2 amp
in a magne tic fie ld B = 0.2Wb/m
2
. The torque acting on
the coil is
C
B A
D
10 cm
8 cm
N
S
(a) 0.32 Nm tending to rotate the side AD out of the page
(b) 0.32 Nm tending to rotate the side AD into the page
(c) 0.0032 Nm tending to rotate the side AD out of the
page
(d) 0.0032 Nm tending to rotate the side AD into the page
Q.7 A rectangular coil of size 20 cm × 20 cm has 100 turns
and carries a current of 1 A. It is placed in a uniform
magnetic field B = 0.5 T with the direction of magnetic
field parallel to the plane of the coil. The magnitude of the
torque required to hold this coil in this position is
(a) zero (b) 200 Nm
(c) 2 Nm (d) 10 Nm
Q.8 A circular loop of area 0.01m
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) zero (b) 0.01 Nm
(c) 0.001 N m (d) 0.8 Nm
Q.9 The magnetic moment of a current carrying circular coil is
(a) directly proportional to the length of the wire
(b) inversely proportional to the length of the wire
(c) directly proportional to the square of the length of
the wire
(d) inversely proportional to the square of the length of
the wire
Q.10 What is the shape of magnet in moving coil galvanometer
to make the radial magnetic field?
(a) Concave cylindrical (b) Horse shoe magnet
(c) Convex cylindrical (d) None of these
Q.11 Current i is carried in a wire of length L. If the wire is
turned into a circular coil, the maximum magnitude of
torque in a given magnetic field B will be
(a)
2
2
LiB
(b)
2
2
LiB
(c)
2
4
L iB
p
(d)
2
4
LiB
p
Q.12 In ballistic galvanometer, the frame on which the coil is
wound is non-metallic. It is
(a) to avoid the production of induced e.m.f.
(b) to avoid the production of eddy currents
(c) to increase the production of eddy currents
(d) to increase the production of induced e.m.f.
Q.13 A solenoid of length 0.4 m and having 500 turns of wire
carries a current of 3 amp. A thin coil having 10 turns of wire
and of radius 0.01 m carries a current of 0.4 amp. The torque
(in Nm) required to hold the coil in the middle of the solenoid
with its axis perpendicular to the axis of the solenoid is
(m
0
= 4p × 10
–7
V -s/A-m)
(a) 59.2 × 10
–6
(b) 5.92 × 10
–6
(c) 0.592 × 10
–6
(d) 0.592 × 10
–4
.
Q.14 If an electron is moving with velocity v in an orbit of radius
r in a hydrogen atom, then the equivalent magnetic moment is
(a)
0
µe
2r
(b)
2
ev
r
(c)
7
3
ev 10
r
,
´
(d)
evr
2
Q.15 In a moving coil galvanometer, the deflection of the coil q is
related to the electrical current i by the relation
(a) i µ tan q (b) i µ q
(c) i µ q
2
(d) iµq
Q.16 A thin circular wire carrying a current I has a magnetic
moment M. The shape of the wire is changed to a square
and it carries the same current. It will have a magnetic
moment
(a) M (b)
2
4
M
p
(c)
4
M
p
(d)
4
M
p
Q.17 A ring of radius R, made of an insulating material carries a
charge Q uniformly distributed on it. If the ring rotates about
the axis passing through its centre and normal to plane of
the ring with constant angular speed w, then the magnitude
of the magnetic moment of the ring is
(a)
2
QR w (b)
2
1
2
QR w (c)
2
QR w (d)
2
1
2
QR w
DPP/ P 41
3
Q.18 The (t - q) graph for a current carrying coil placed in a
uniform magnetic field is
(a)
0°
180° 90°
q
(b)
0°
180° 90°
q
(c)
0°
180° 90°
q
(d)
0°
180° 90°
q
Q.19A rectangular loop carrying a current i is placed in a
uniform magnetic field B. The area enclosed by the loop
is A. If there are n turns in the loop, the torque acting on
the loop is given by
(a) niAB ´
r r
(b) ni A.B
r r
(c)
1
(i A B)
n
´
r r
(d)
1
(iA.B)
n
r r
Q.20The pole pieces of the magnet used in a pivoted coil
galvanometer are
(a) plane surfaces of a bar magnet
(b) plane surfaces of a horse-shoe magnet
(c) cylindrical surfaces of a bar magnet
(d) cylindrical surfaces of a horse-shoe magnet
DIRECTIONS (Q.21-Q.23) : In the following questions,
more than one of the answers given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.21 Four wires each of length 2.0 metre are bent into four loops
P, Q, R and S and then suspended into uniform magnetic
field. Same current is passed in each loop. Which
statements are incorrect?
P
Q R
S
(1) Couple on loop P will be the highest
(2) Couple on loop Q will be the highest
(3) Couple on loop R will be the highest
(4) Couple on loop S will be the highest
Q.22The sensitivity of a moving coil galvanometer can be
increased by
(1) decreasing the couple per unit twist of the suspension
(2) increasing the number of turns in the coil
(3) decreasing the area of the coil
(4) decreasing the magnetic field
Q.23A current carrying rectangular coil is placed in a uniform
magnetic field. In which orientation, the coil will tend to
rotate
(1) The magnetic field is parallel to the plane of the coil
(2) The magnetic field is at 45° with the plane of the coil
(3) In any orientation
(4) The magnetic field is perpendicular to the plane of
the coil
DIRECTIONS (Q.24-Q.26) : Read the passage given below
and answer the questions that follows :
A wire carrying a 10 A current is
bent to pass through sides of a cube
of side 10 cm as shown in figure. A
magnetic field
ˆ ˆˆ
B (2i 3j k)T = -+
r
is
present in the region. Then, find
2
y
z
4
x
1
3
Q.24 The net force on the loop
(a)
net
F0 =
r
(b)
net
ˆˆ
F (0.1i 0.2k)N =-
r
(c)
net
ˆˆ
F (0.3i 0.4k)N =+
r
(d)
net
ˆ
F (0.36k)N =
r
Q.25 The magnetic moment vector of the loop.
(a)
2
ˆ ˆˆ
(0.1i 0.05j 0.05k)Am +- (b)
2
ˆ ˆˆ
(0.1i 0.05j 0.05k)Am ++
(c)
2
ˆ ˆˆ
(0.1i 0.05j 0.05k)Am -+ (d)
2
ˆ ˆˆ
(0.1i 0.05j 0.05k)Am --
4
DPP/ P 41
Q.26 The net torque on the loop.
(a)
ˆˆ
0.1i 0.4k Nm -+ (b)
ˆˆ
0.1i 0.4k Nm --
(c)
ˆˆ
0.1i 0.4k Nm - (d)
ˆˆ
0.1i 0.4k Nm -
DIRECTIONS (Q. 27-Q.29) : Each of these questions contains
two statements: Statement-1 (Assertion) and Statement-2
(Reason). Each of these questions has four alternative choices,
only one of which is the correct answer. You have to select the
correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement-1 is False, Statement-2 is True.
(d) Statement-1 is True, Statement-2 is False.
Q.27 Statement-1 : The coil is bound over the metallic frame
in moving coil galvanometer.
Statement-2 : The metallic frame help in making steady
deflection without any oscillation.
Q.28 Statement-1 : Torque on the coil is maximum, when coil
is suspended in a radial magnetic field.
Statement-2 : The torque tends to rotate the coil on its
own axis.
Q.29Statement-1 : A current carrying loop placed in
equilibrium in a uniform magnetic field starts oscillating
when disturbed from equilibrium.
Statement-2 : A system when disturbed slightly from stable
equilibrium oscillates.
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