Magnetism and Matter- 1 Practice Questions - DPP for NEET

 Page 1


DIRECTIONS (Q.1-Q.21) : There are 21 mul1tiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A north pole of strength 50 Am and south pole of strength
100 Am are separated by a distance of 10 cm in air. Find
the force between them.
(a) 50 × 10
–3
 N (b) 25 × 10
–3
 N
(c) 20 × 10
–6
 N (d) 30 × 10
–18
 N
Q.2 Calculate magnetic induction at a distance of 20 cm from
a pole of strength 40 Am in air.
(a) 10
–4
 wb/m
2
(b) 10
–8
 wb/m
2
(c) 10
–1
 wb/m
2
(d) 10
–12
 wb/m
2
Q.3 A bar magnet of length 0.2 m and pole strength 5 Am is
kept in a uniform magnetic induction field of strength 15
wb/m
–2
 making an angle of 30° with the field. Find the
couple acting on it.
(a) 2.5 Nm (b) 5.5 Nm (c) 7.5 Nm (d) 9.0 Nm
Q.4 The force experienced by a pole of strength 100 Am at a
distance of 0.2 m from a short magnet of length 5 cm and
pole strength of 200 Am on its axial line will be
(a) 2.5 × 10
-2
 N (b) 2.5 × 10
-3
 N
(c) 5.0 × 10
-2 
N (d) 5.0 × 10
-3
 N
Q.5 A magnet of moment M is ly ing in a magnetic field of induction
B. W
1
 is the work done in turning it from 0º to 60º and W
2
 is
the work done in turning it from 30º to 90º. Then
(a)W
2
 = W
1
(b)W
2
 = 
1
W
2
(c)W
2
 = 2W
1
(d)W
2
 = 
3
W
1
Page 2


DIRECTIONS (Q.1-Q.21) : There are 21 mul1tiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A north pole of strength 50 Am and south pole of strength
100 Am are separated by a distance of 10 cm in air. Find
the force between them.
(a) 50 × 10
–3
 N (b) 25 × 10
–3
 N
(c) 20 × 10
–6
 N (d) 30 × 10
–18
 N
Q.2 Calculate magnetic induction at a distance of 20 cm from
a pole of strength 40 Am in air.
(a) 10
–4
 wb/m
2
(b) 10
–8
 wb/m
2
(c) 10
–1
 wb/m
2
(d) 10
–12
 wb/m
2
Q.3 A bar magnet of length 0.2 m and pole strength 5 Am is
kept in a uniform magnetic induction field of strength 15
wb/m
–2
 making an angle of 30° with the field. Find the
couple acting on it.
(a) 2.5 Nm (b) 5.5 Nm (c) 7.5 Nm (d) 9.0 Nm
Q.4 The force experienced by a pole of strength 100 Am at a
distance of 0.2 m from a short magnet of length 5 cm and
pole strength of 200 Am on its axial line will be
(a) 2.5 × 10
-2
 N (b) 2.5 × 10
-3
 N
(c) 5.0 × 10
-2 
N (d) 5.0 × 10
-3
 N
Q.5 A magnet of moment M is ly ing in a magnetic field of induction
B. W
1
 is the work done in turning it from 0º to 60º and W
2
 is
the work done in turning it from 30º to 90º. Then
(a)W
2
 = W
1
(b)W
2
 = 
1
W
2
(c)W
2
 = 2W
1
(d)W
2
 = 
3
W
1
2
DPP/ P 42
Q.6 A bar magnet of magnetic moment 4.0 A-m
2
 is free to rotate
about a vertical axis through its centre. The magnet is
released from rest from east-west position. Kinetic energy
of the magnet in north-south position will be (Horizontal
component of earth’s magnetic field B
H 
= 25 mT)
(a) 10
-2
 J (b) 10
-4
 J (c) 10
-6
 J (d)0
Q.7 The length of a bar magnet is 10 cm and its pole strength is
10
-3
 Weber. It is placed in a magnetic field of induction
4 p × 10
-3
 Tesla in a direction making an angle 30º with
the field direction. The value of torque acting on the magnet
will be –
(a)2p × 10
-7
 N-m (b)2p × 10
-5
 N-m
(c) 0.5 × 10
2
 N-m (d) None of these
Q.8 At magnetic poles of earth, angle of dip is
(a) zero (b) 45° (c) 90
°
(d) 180
°
Q.9 A short bar magnet is placed with its north pole pointing
south. The neutral point is 10 cm away from the centre of
the magnet. If H = 0.4 gauss, calculate magnetic moment
of the magnet.
(a) 2 Am
2
(b) 1A m
2
(c) 0.1 A m
2
(d) 0.2 Am
2
Q.10 A bar magnet with its poles 25 cm apart and of pole strength
24.0 A-m rests with its centre on a frictionless pivot. A
force F is applied on the magnet at a distance of 12 cm
from the pivot, so that it is held in equilibrium at an angle
of 30º with respect to a magnetic field of induction 0.25
T. The value of force F is
(a) 65.62 N (b) 2.56 N (c) 6.52 N (d) 6.25 N
Q.11 A small magnet of magnetic moment 4A-m
2
 is placed on a
deflection magnetometer in tan-B position at a distance
of 20cm from the compass needle. At what distance from
compass needle should another small magnet of moment
0.5A-m
2
 be placed such that the deflection of the needle
remains zero ?
(a) 12 cm (b) 10 cm (c) 20 cm (d) 30 cm
Q.12The ratio of intensities of magnetic field, at distances x
and 2x from the centre of magnet of length 2cm on its
axis, will be
(a) 4 : 1 (b) 4 : 1 approx
(c) 8 : 1 (d) 8 : 1 approx
Q.13 Two magnets A and B are identical and these are arranged
as shown in the figure. Their length is negligible in
comparison to the separation between them. A magnetic
needle is placed between the magnets at point P which gets
deflected through an angle q under the influence of
magnets. The ratio of distances d
1
 and d
2
 will be
(a) (2 tan q)
1/3
(b) (2 tan q)
-1/3
d
1
d
2
A
P
B
q
(c) (2 cot q)
1/3
(d) (2 cot q)
-1/3
Q.14 The period of oscillation of a freely suspended bar magnet
is 4 second. If it is cut into two equal parts length wise
then the time period of each part will be
(a) 4 sec (b) 2 sec (c) 0.5 sec (d) 0.25 sec
Q.15 The length, breadth and mass of two bar magnets are same
but their magnetic moments are 3M and 2M respectively.
These are joined pole to pole and are suspended by a string.
When oscillated in a magnetic field of strength B, the time
period obtained is 5s. If the poles of either of the magnets
are reverse then the time period of the combination in the
same magnetic field will be –
(a) 3 3s (b) 2 2s (c) 5 5s (d) 1s
Q.16 A thin magnetic needle oscillates in a horizontal plane with
a period T. It is broken into n equals parts.  The time period
of each part will be
(a)T (b)
T
n
(c) Tn
2
(d)
2
T
n
Q.17 A bar magnet made of steel has a magnetic moment of 2.5 A-
m
2
 and a mass of  6.6 × 10
3
 kg. If the density of steel is
7.9 × 10
9
 kg/m
3
, find the intensity of magnetization of the
magnet.
(a) 3.0 × 10
6
 A/m (b) 2.0 × 10
6
 A/m
(c) 5.0 × 10
6
 A/m (d) 1.2 × 10
6
 A/m
Q.18 A short magnet of length 4 cm is kept at a distance of 20
cm to the east of a compass box such that is axis is
perpendicular to the magnetic meridian. If the deflection
produced is 45°, find the pole strength (H = 30 Am
–1
)
(a) 17.7 Am (b) 44.2 Am
(c) 27.7 Am (d) 37.7 Am
Page 3


DIRECTIONS (Q.1-Q.21) : There are 21 mul1tiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A north pole of strength 50 Am and south pole of strength
100 Am are separated by a distance of 10 cm in air. Find
the force between them.
(a) 50 × 10
–3
 N (b) 25 × 10
–3
 N
(c) 20 × 10
–6
 N (d) 30 × 10
–18
 N
Q.2 Calculate magnetic induction at a distance of 20 cm from
a pole of strength 40 Am in air.
(a) 10
–4
 wb/m
2
(b) 10
–8
 wb/m
2
(c) 10
–1
 wb/m
2
(d) 10
–12
 wb/m
2
Q.3 A bar magnet of length 0.2 m and pole strength 5 Am is
kept in a uniform magnetic induction field of strength 15
wb/m
–2
 making an angle of 30° with the field. Find the
couple acting on it.
(a) 2.5 Nm (b) 5.5 Nm (c) 7.5 Nm (d) 9.0 Nm
Q.4 The force experienced by a pole of strength 100 Am at a
distance of 0.2 m from a short magnet of length 5 cm and
pole strength of 200 Am on its axial line will be
(a) 2.5 × 10
-2
 N (b) 2.5 × 10
-3
 N
(c) 5.0 × 10
-2 
N (d) 5.0 × 10
-3
 N
Q.5 A magnet of moment M is ly ing in a magnetic field of induction
B. W
1
 is the work done in turning it from 0º to 60º and W
2
 is
the work done in turning it from 30º to 90º. Then
(a)W
2
 = W
1
(b)W
2
 = 
1
W
2
(c)W
2
 = 2W
1
(d)W
2
 = 
3
W
1
2
DPP/ P 42
Q.6 A bar magnet of magnetic moment 4.0 A-m
2
 is free to rotate
about a vertical axis through its centre. The magnet is
released from rest from east-west position. Kinetic energy
of the magnet in north-south position will be (Horizontal
component of earth’s magnetic field B
H 
= 25 mT)
(a) 10
-2
 J (b) 10
-4
 J (c) 10
-6
 J (d)0
Q.7 The length of a bar magnet is 10 cm and its pole strength is
10
-3
 Weber. It is placed in a magnetic field of induction
4 p × 10
-3
 Tesla in a direction making an angle 30º with
the field direction. The value of torque acting on the magnet
will be –
(a)2p × 10
-7
 N-m (b)2p × 10
-5
 N-m
(c) 0.5 × 10
2
 N-m (d) None of these
Q.8 At magnetic poles of earth, angle of dip is
(a) zero (b) 45° (c) 90
°
(d) 180
°
Q.9 A short bar magnet is placed with its north pole pointing
south. The neutral point is 10 cm away from the centre of
the magnet. If H = 0.4 gauss, calculate magnetic moment
of the magnet.
(a) 2 Am
2
(b) 1A m
2
(c) 0.1 A m
2
(d) 0.2 Am
2
Q.10 A bar magnet with its poles 25 cm apart and of pole strength
24.0 A-m rests with its centre on a frictionless pivot. A
force F is applied on the magnet at a distance of 12 cm
from the pivot, so that it is held in equilibrium at an angle
of 30º with respect to a magnetic field of induction 0.25
T. The value of force F is
(a) 65.62 N (b) 2.56 N (c) 6.52 N (d) 6.25 N
Q.11 A small magnet of magnetic moment 4A-m
2
 is placed on a
deflection magnetometer in tan-B position at a distance
of 20cm from the compass needle. At what distance from
compass needle should another small magnet of moment
0.5A-m
2
 be placed such that the deflection of the needle
remains zero ?
(a) 12 cm (b) 10 cm (c) 20 cm (d) 30 cm
Q.12The ratio of intensities of magnetic field, at distances x
and 2x from the centre of magnet of length 2cm on its
axis, will be
(a) 4 : 1 (b) 4 : 1 approx
(c) 8 : 1 (d) 8 : 1 approx
Q.13 Two magnets A and B are identical and these are arranged
as shown in the figure. Their length is negligible in
comparison to the separation between them. A magnetic
needle is placed between the magnets at point P which gets
deflected through an angle q under the influence of
magnets. The ratio of distances d
1
 and d
2
 will be
(a) (2 tan q)
1/3
(b) (2 tan q)
-1/3
d
1
d
2
A
P
B
q
(c) (2 cot q)
1/3
(d) (2 cot q)
-1/3
Q.14 The period of oscillation of a freely suspended bar magnet
is 4 second. If it is cut into two equal parts length wise
then the time period of each part will be
(a) 4 sec (b) 2 sec (c) 0.5 sec (d) 0.25 sec
Q.15 The length, breadth and mass of two bar magnets are same
but their magnetic moments are 3M and 2M respectively.
These are joined pole to pole and are suspended by a string.
When oscillated in a magnetic field of strength B, the time
period obtained is 5s. If the poles of either of the magnets
are reverse then the time period of the combination in the
same magnetic field will be –
(a) 3 3s (b) 2 2s (c) 5 5s (d) 1s
Q.16 A thin magnetic needle oscillates in a horizontal plane with
a period T. It is broken into n equals parts.  The time period
of each part will be
(a)T (b)
T
n
(c) Tn
2
(d)
2
T
n
Q.17 A bar magnet made of steel has a magnetic moment of 2.5 A-
m
2
 and a mass of  6.6 × 10
3
 kg. If the density of steel is
7.9 × 10
9
 kg/m
3
, find the intensity of magnetization of the
magnet.
(a) 3.0 × 10
6
 A/m (b) 2.0 × 10
6
 A/m
(c) 5.0 × 10
6
 A/m (d) 1.2 × 10
6
 A/m
Q.18 A short magnet of length 4 cm is kept at a distance of 20
cm to the east of a compass box such that is axis is
perpendicular to the magnetic meridian. If the deflection
produced is 45°, find the pole strength (H = 30 Am
–1
)
(a) 17.7 Am (b) 44.2 Am
(c) 27.7 Am (d) 37.7 Am
DPP/ P 42
3
Q.19 A 10 cm long bar magnet of magnetic moment 1.34 Am
2
is placed in the magnetic meridian with its south pole
pointing geographical south. The neutral point is obtained
at a distance of 15 cm from the centre of the magnet.
Calculate the horizontal component of earth’s magnetic
field.
(a) 0.12 × 10
–4
 T (b) 0.21× 10
–4
 T
(c) 0.34 × 10
–4
 T (d) 0.87 × 10
–7
 T
Q.20 A 30 cm long bar magnet is placed in the magnetic meridian
with its north pole pointing south. The neutral point is
obtained at a distance of 40 cm from the centre of the
magnet. Pole strength of the magnet is (The horizontal
component of earth’s magnetic field is 0.34 Gauss)
(a) 26.7 Am (b) 16.7 Am (c) 12.7 Am (d) 15.2 Am
Q.21 A long straight horizontal cable carries a current of 2.5 A
in the direction 10° south of west to 10° north of east. The
magnetic meridian of the place happens to be 10° west of
the geographic meridian. The earth’s magnetic field at the
location is 0.33 Gauss, and the angle of dip is zero.
Distance of the line of neutral points from the cable is
(Ignore the thickness of the cable).
(a) 1.5 cm (b) 2.5 cm (c) 3.5 cm (d) 2.0 cm
DIRECTIONS (Q.22-Q.24) : 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.22Which of the following is/are not the main difference
between electric lines of force and magnetic lines of force
?
(1) Electric lines of force are closed curves whereas
magnetic lines of force are open curves.
(2) Magnetic lines of force cut each other whereas
electric lines of force do not cut.
(3) Electric lines of force cut each other whereas
magnetic lines of force do not cut.
(4) Electric lines of force are open curves whereas
magnetic lines of force are closed curves.
Q.23 The correct statements regarding the lines of force of the
magnetic field B are
(1) Magnetic intensity is a measure of lines of force
passing through unit area held normal to it
(2) Magnetic lines of force form a closed curve
(3) Due to a magnet magnetic lines of force never cut
each other
(4) Inside a magnet, its magnetic lines of force move from
north pole of a magnet towards its south pole
Q.24 A short bar magnet of magnetic moment 5.25 × 10
–2
 JT
–1
is placed with its axis perpendicular to the earth’s field
direction. Magnitude of the earth’s field at the place is given
to be 0.42 G . Ignore the length of the magnet in comparison
to the distance involved. Then
(1) the distance from the centre of the magnet on its
normal bisector at which the resultant field is inclined
at 45° with the earth's field is 5 cm
(2) the distance from the centre of the magnet on its axis
at which the resultant field inclined at 45° with the
earth's field is 6.3 cm
(3) the distance from the centre of the magnet on its
normal bisector at which the resultant field inclined
at 45° with the earth's field is 8.3 cm
(4) the distance from the centre of the magnet on its axis
at which the resultant field inclined at 45° with the
earth's field is 8 cm
DIRECTIONS (Q.25-Q.27) : Read the passage given below
and answer the questions that follows :
A telephone cable at a place has four long, straight horizontal wires
carrying a current of 1.0 A in the same direction east to west. The
earth’s magnetic field at the place is 0.39 Gauss, and the angle of
dip is 35°. The magnetic declination is nearly zero. (cos 35° =
0.82, sin 35° = 0.57)
Q.25The magnetic field produced by four current carrying
straight cable wires at a distance 4 cm is
(a) 0.2 Gauss (b) 0.3 Gauss
(c) 0.4 Gauss (d) 0.5 Gauss
Q.26 The resultant magnetic field  below at points 4cm and above
the cable are
(a) 0.25, 0.56 Gauss (b) 0.14, 0.32 Gauss
(c) 0.23, 0.34 Gauss (d) 0.52, 0.62 Gauss
Page 4


DIRECTIONS (Q.1-Q.21) : There are 21 mul1tiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A north pole of strength 50 Am and south pole of strength
100 Am are separated by a distance of 10 cm in air. Find
the force between them.
(a) 50 × 10
–3
 N (b) 25 × 10
–3
 N
(c) 20 × 10
–6
 N (d) 30 × 10
–18
 N
Q.2 Calculate magnetic induction at a distance of 20 cm from
a pole of strength 40 Am in air.
(a) 10
–4
 wb/m
2
(b) 10
–8
 wb/m
2
(c) 10
–1
 wb/m
2
(d) 10
–12
 wb/m
2
Q.3 A bar magnet of length 0.2 m and pole strength 5 Am is
kept in a uniform magnetic induction field of strength 15
wb/m
–2
 making an angle of 30° with the field. Find the
couple acting on it.
(a) 2.5 Nm (b) 5.5 Nm (c) 7.5 Nm (d) 9.0 Nm
Q.4 The force experienced by a pole of strength 100 Am at a
distance of 0.2 m from a short magnet of length 5 cm and
pole strength of 200 Am on its axial line will be
(a) 2.5 × 10
-2
 N (b) 2.5 × 10
-3
 N
(c) 5.0 × 10
-2 
N (d) 5.0 × 10
-3
 N
Q.5 A magnet of moment M is ly ing in a magnetic field of induction
B. W
1
 is the work done in turning it from 0º to 60º and W
2
 is
the work done in turning it from 30º to 90º. Then
(a)W
2
 = W
1
(b)W
2
 = 
1
W
2
(c)W
2
 = 2W
1
(d)W
2
 = 
3
W
1
2
DPP/ P 42
Q.6 A bar magnet of magnetic moment 4.0 A-m
2
 is free to rotate
about a vertical axis through its centre. The magnet is
released from rest from east-west position. Kinetic energy
of the magnet in north-south position will be (Horizontal
component of earth’s magnetic field B
H 
= 25 mT)
(a) 10
-2
 J (b) 10
-4
 J (c) 10
-6
 J (d)0
Q.7 The length of a bar magnet is 10 cm and its pole strength is
10
-3
 Weber. It is placed in a magnetic field of induction
4 p × 10
-3
 Tesla in a direction making an angle 30º with
the field direction. The value of torque acting on the magnet
will be –
(a)2p × 10
-7
 N-m (b)2p × 10
-5
 N-m
(c) 0.5 × 10
2
 N-m (d) None of these
Q.8 At magnetic poles of earth, angle of dip is
(a) zero (b) 45° (c) 90
°
(d) 180
°
Q.9 A short bar magnet is placed with its north pole pointing
south. The neutral point is 10 cm away from the centre of
the magnet. If H = 0.4 gauss, calculate magnetic moment
of the magnet.
(a) 2 Am
2
(b) 1A m
2
(c) 0.1 A m
2
(d) 0.2 Am
2
Q.10 A bar magnet with its poles 25 cm apart and of pole strength
24.0 A-m rests with its centre on a frictionless pivot. A
force F is applied on the magnet at a distance of 12 cm
from the pivot, so that it is held in equilibrium at an angle
of 30º with respect to a magnetic field of induction 0.25
T. The value of force F is
(a) 65.62 N (b) 2.56 N (c) 6.52 N (d) 6.25 N
Q.11 A small magnet of magnetic moment 4A-m
2
 is placed on a
deflection magnetometer in tan-B position at a distance
of 20cm from the compass needle. At what distance from
compass needle should another small magnet of moment
0.5A-m
2
 be placed such that the deflection of the needle
remains zero ?
(a) 12 cm (b) 10 cm (c) 20 cm (d) 30 cm
Q.12The ratio of intensities of magnetic field, at distances x
and 2x from the centre of magnet of length 2cm on its
axis, will be
(a) 4 : 1 (b) 4 : 1 approx
(c) 8 : 1 (d) 8 : 1 approx
Q.13 Two magnets A and B are identical and these are arranged
as shown in the figure. Their length is negligible in
comparison to the separation between them. A magnetic
needle is placed between the magnets at point P which gets
deflected through an angle q under the influence of
magnets. The ratio of distances d
1
 and d
2
 will be
(a) (2 tan q)
1/3
(b) (2 tan q)
-1/3
d
1
d
2
A
P
B
q
(c) (2 cot q)
1/3
(d) (2 cot q)
-1/3
Q.14 The period of oscillation of a freely suspended bar magnet
is 4 second. If it is cut into two equal parts length wise
then the time period of each part will be
(a) 4 sec (b) 2 sec (c) 0.5 sec (d) 0.25 sec
Q.15 The length, breadth and mass of two bar magnets are same
but their magnetic moments are 3M and 2M respectively.
These are joined pole to pole and are suspended by a string.
When oscillated in a magnetic field of strength B, the time
period obtained is 5s. If the poles of either of the magnets
are reverse then the time period of the combination in the
same magnetic field will be –
(a) 3 3s (b) 2 2s (c) 5 5s (d) 1s
Q.16 A thin magnetic needle oscillates in a horizontal plane with
a period T. It is broken into n equals parts.  The time period
of each part will be
(a)T (b)
T
n
(c) Tn
2
(d)
2
T
n
Q.17 A bar magnet made of steel has a magnetic moment of 2.5 A-
m
2
 and a mass of  6.6 × 10
3
 kg. If the density of steel is
7.9 × 10
9
 kg/m
3
, find the intensity of magnetization of the
magnet.
(a) 3.0 × 10
6
 A/m (b) 2.0 × 10
6
 A/m
(c) 5.0 × 10
6
 A/m (d) 1.2 × 10
6
 A/m
Q.18 A short magnet of length 4 cm is kept at a distance of 20
cm to the east of a compass box such that is axis is
perpendicular to the magnetic meridian. If the deflection
produced is 45°, find the pole strength (H = 30 Am
–1
)
(a) 17.7 Am (b) 44.2 Am
(c) 27.7 Am (d) 37.7 Am
DPP/ P 42
3
Q.19 A 10 cm long bar magnet of magnetic moment 1.34 Am
2
is placed in the magnetic meridian with its south pole
pointing geographical south. The neutral point is obtained
at a distance of 15 cm from the centre of the magnet.
Calculate the horizontal component of earth’s magnetic
field.
(a) 0.12 × 10
–4
 T (b) 0.21× 10
–4
 T
(c) 0.34 × 10
–4
 T (d) 0.87 × 10
–7
 T
Q.20 A 30 cm long bar magnet is placed in the magnetic meridian
with its north pole pointing south. The neutral point is
obtained at a distance of 40 cm from the centre of the
magnet. Pole strength of the magnet is (The horizontal
component of earth’s magnetic field is 0.34 Gauss)
(a) 26.7 Am (b) 16.7 Am (c) 12.7 Am (d) 15.2 Am
Q.21 A long straight horizontal cable carries a current of 2.5 A
in the direction 10° south of west to 10° north of east. The
magnetic meridian of the place happens to be 10° west of
the geographic meridian. The earth’s magnetic field at the
location is 0.33 Gauss, and the angle of dip is zero.
Distance of the line of neutral points from the cable is
(Ignore the thickness of the cable).
(a) 1.5 cm (b) 2.5 cm (c) 3.5 cm (d) 2.0 cm
DIRECTIONS (Q.22-Q.24) : 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.22Which of the following is/are not the main difference
between electric lines of force and magnetic lines of force
?
(1) Electric lines of force are closed curves whereas
magnetic lines of force are open curves.
(2) Magnetic lines of force cut each other whereas
electric lines of force do not cut.
(3) Electric lines of force cut each other whereas
magnetic lines of force do not cut.
(4) Electric lines of force are open curves whereas
magnetic lines of force are closed curves.
Q.23 The correct statements regarding the lines of force of the
magnetic field B are
(1) Magnetic intensity is a measure of lines of force
passing through unit area held normal to it
(2) Magnetic lines of force form a closed curve
(3) Due to a magnet magnetic lines of force never cut
each other
(4) Inside a magnet, its magnetic lines of force move from
north pole of a magnet towards its south pole
Q.24 A short bar magnet of magnetic moment 5.25 × 10
–2
 JT
–1
is placed with its axis perpendicular to the earth’s field
direction. Magnitude of the earth’s field at the place is given
to be 0.42 G . Ignore the length of the magnet in comparison
to the distance involved. Then
(1) the distance from the centre of the magnet on its
normal bisector at which the resultant field is inclined
at 45° with the earth's field is 5 cm
(2) the distance from the centre of the magnet on its axis
at which the resultant field inclined at 45° with the
earth's field is 6.3 cm
(3) the distance from the centre of the magnet on its
normal bisector at which the resultant field inclined
at 45° with the earth's field is 8.3 cm
(4) the distance from the centre of the magnet on its axis
at which the resultant field inclined at 45° with the
earth's field is 8 cm
DIRECTIONS (Q.25-Q.27) : Read the passage given below
and answer the questions that follows :
A telephone cable at a place has four long, straight horizontal wires
carrying a current of 1.0 A in the same direction east to west. The
earth’s magnetic field at the place is 0.39 Gauss, and the angle of
dip is 35°. The magnetic declination is nearly zero. (cos 35° =
0.82, sin 35° = 0.57)
Q.25The magnetic field produced by four current carrying
straight cable wires at a distance 4 cm is
(a) 0.2 Gauss (b) 0.3 Gauss
(c) 0.4 Gauss (d) 0.5 Gauss
Q.26 The resultant magnetic field  below at points 4cm and above
the cable are
(a) 0.25, 0.56 Gauss (b) 0.14, 0.32 Gauss
(c) 0.23, 0.34 Gauss (d) 0.52, 0.62 Gauss
4
DPP/ P 42
Q.27 The angle that resultant makes with horizontal in case below
and above the cable respectively, are
(a) 30°, 45° (b) tan
–1
 1.8, tan
–1
 0.43
(c) tan
–1
 2, tan
–1
2 (d) sin
–1
 0.7, sin
–1
 0.9
DIRECTIONS (Q. 28-Q.30) : 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.28Statement-1 : Gauss theorem is not applicable in
magnetism.
Statement-2 : Mono magnetic pole does not exist.
Q.29 Statement-1 : A compass needle when placed on the
magnetic north pole of the earth cannot rotate in vertical
direction.
Statement-2 : The earth has only horizontal component
of its magnetic field at the north poles.
Q.30Statement-1 : We cannot think of magnetic field
configuration with three poles.
Statement-2 : A bar magnet does not exert a torque on
itself due to its own field.