Magnetism and Matter Practice Questions - DPP for JEE

 Page 1


PART-I (Single Correct MCQs)
1. Two identical thin bar magnets each of length l
and pole strength m are placed at right angles to
each other, with north pole of one touching south
pole of the other, then the magnetic moment of
the system is
(a) 1 m l
(b) 2 m l
(c)  m l
(d) m l/2
2. If the period of oscillation of freely suspended bar magnet in earth’s
horizontal field H is 4 sec. When another magnet is brought near it, the
period of oscillation is reduced to 2s. The magnetic field of second bar
magnet is
(a) 4 H
(b) 3 H
Page 2


PART-I (Single Correct MCQs)
1. Two identical thin bar magnets each of length l
and pole strength m are placed at right angles to
each other, with north pole of one touching south
pole of the other, then the magnetic moment of
the system is
(a) 1 m l
(b) 2 m l
(c)  m l
(d) m l/2
2. If the period of oscillation of freely suspended bar magnet in earth’s
horizontal field H is 4 sec. When another magnet is brought near it, the
period of oscillation is reduced to 2s. The magnetic field of second bar
magnet is
(a) 4 H
(b) 3 H
(c) 2 H
(d) H
3. A coil in the shape of an equilateral triangle of side l is suspended between
the pole pieces of a permanent magnet such that  is in the 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)
(b)
(c)
(d)
4. A compass needle whose magnetic moment is 60 Am
2
, is directed
towards geographical north at any place experiencing moment of force
of 1.2 × 10
–3
 Nm. At that place the horizontal component of earth field
is 40 micro W/m
2
. What is the value of dip angle at that place?
(a) 30°
(b) 60°
(c) 45°
(d) 15°
5. The materials suitable for making electromagnets should have
(a) high retentivity and low coercivity
(b) low retentivity and low coercivity
(c) high retentivity and high coercivity
(d) low retentivity and high coercivity
Page 3


PART-I (Single Correct MCQs)
1. Two identical thin bar magnets each of length l
and pole strength m are placed at right angles to
each other, with north pole of one touching south
pole of the other, then the magnetic moment of
the system is
(a) 1 m l
(b) 2 m l
(c)  m l
(d) m l/2
2. If the period of oscillation of freely suspended bar magnet in earth’s
horizontal field H is 4 sec. When another magnet is brought near it, the
period of oscillation is reduced to 2s. The magnetic field of second bar
magnet is
(a) 4 H
(b) 3 H
(c) 2 H
(d) H
3. A coil in the shape of an equilateral triangle of side l is suspended between
the pole pieces of a permanent magnet such that  is in the 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)
(b)
(c)
(d)
4. A compass needle whose magnetic moment is 60 Am
2
, is directed
towards geographical north at any place experiencing moment of force
of 1.2 × 10
–3
 Nm. At that place the horizontal component of earth field
is 40 micro W/m
2
. What is the value of dip angle at that place?
(a) 30°
(b) 60°
(c) 45°
(d) 15°
5. The materials suitable for making electromagnets should have
(a) high retentivity and low coercivity
(b) low retentivity and low coercivity
(c) high retentivity and high coercivity
(d) low retentivity and high coercivity
6. The length of a magnet is large compared to its width and breadth. The
time period of its oscillation in a vibration magnetometer is 2s. The
magnet is cut along its length into three equal parts and these parts are
then placed on each other with their like poles together. The time period
of this combination will be
(a)
(b)
(c) 2 s
(d)
7. A magnetic dipole is under the influence of two magnetic fields The
angle between the field directions is 60° and one of the fields has a
magnitude of 1.2 × 10
–2
 T. If the dipole comes to stable equilibrium at
an angle of 15° with this field, what is the magnitude of other field ?
(a) 4.4 × 10
–3
 tesla
(b) 5.2 × 10
–3
 tesla
(c) 3.4 × 10
–3
 tesla
(d) 7.8 × 10
–3
 tesla
8. A bar magnet 8 cm long is placed in the magnetic merdian with the N-
pole pointing towards geographical north. Two netural points separated
by a distance of 6 cms are obtained on the equatorial axis of the magnet.
If horizontal component of earth’s field = 3.2 × 10
–5
 T, then pole strength
of magnet is
(a) 5 ab-amp × cm
(b) 10 ab-amp × cm
(c) 2.5 ab-amp × cm
(d) 20 ab-amp × cm
9. If the susceptibility of dia, para and ferro magnetic materials are ?
d
, ?
p
,
?
f
 respectively, then
Page 4


PART-I (Single Correct MCQs)
1. Two identical thin bar magnets each of length l
and pole strength m are placed at right angles to
each other, with north pole of one touching south
pole of the other, then the magnetic moment of
the system is
(a) 1 m l
(b) 2 m l
(c)  m l
(d) m l/2
2. If the period of oscillation of freely suspended bar magnet in earth’s
horizontal field H is 4 sec. When another magnet is brought near it, the
period of oscillation is reduced to 2s. The magnetic field of second bar
magnet is
(a) 4 H
(b) 3 H
(c) 2 H
(d) H
3. A coil in the shape of an equilateral triangle of side l is suspended between
the pole pieces of a permanent magnet such that  is in the 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)
(b)
(c)
(d)
4. A compass needle whose magnetic moment is 60 Am
2
, is directed
towards geographical north at any place experiencing moment of force
of 1.2 × 10
–3
 Nm. At that place the horizontal component of earth field
is 40 micro W/m
2
. What is the value of dip angle at that place?
(a) 30°
(b) 60°
(c) 45°
(d) 15°
5. The materials suitable for making electromagnets should have
(a) high retentivity and low coercivity
(b) low retentivity and low coercivity
(c) high retentivity and high coercivity
(d) low retentivity and high coercivity
6. The length of a magnet is large compared to its width and breadth. The
time period of its oscillation in a vibration magnetometer is 2s. The
magnet is cut along its length into three equal parts and these parts are
then placed on each other with their like poles together. The time period
of this combination will be
(a)
(b)
(c) 2 s
(d)
7. A magnetic dipole is under the influence of two magnetic fields The
angle between the field directions is 60° and one of the fields has a
magnitude of 1.2 × 10
–2
 T. If the dipole comes to stable equilibrium at
an angle of 15° with this field, what is the magnitude of other field ?
(a) 4.4 × 10
–3
 tesla
(b) 5.2 × 10
–3
 tesla
(c) 3.4 × 10
–3
 tesla
(d) 7.8 × 10
–3
 tesla
8. A bar magnet 8 cm long is placed in the magnetic merdian with the N-
pole pointing towards geographical north. Two netural points separated
by a distance of 6 cms are obtained on the equatorial axis of the magnet.
If horizontal component of earth’s field = 3.2 × 10
–5
 T, then pole strength
of magnet is
(a) 5 ab-amp × cm
(b) 10 ab-amp × cm
(c) 2.5 ab-amp × cm
(d) 20 ab-amp × cm
9. If the susceptibility of dia, para and ferro magnetic materials are ?
d
, ?
p
,
?
f
 respectively, then
(a) ?
d
 < ?
p
 < ?
f
(b) ?
d
 < ?
f
 < ?
p
(c) ?
f
 < ?
d
 < ?
p
(d) ?
f
 < ?
p
 < ?
d
10. The figure shows the various positions (labelled
by subscripts) of small magnetised needles P
and Q. The arrows show the direction of their
magnetic moment. Which configuration
corresponds to the lowest potential energy
among all the configurations shown ?
(a) PQ
3
(b) PQ
4
(c) PQ
5
(d) PQ
6
11. The angle of dip at a place is 37° and the vertical component of the
earth’s magnetic field is 6 × 10
–5
T. The earth’s magnetic field at this
place is (tan 37° = 3/4)
(a) 7 × 10
–5
 T
(b) 6 × 10
–5
 T
(c) 5 × 10
–5
 T
(d) 10
–4
 T
12. Needles N
1
, N
2
 and N
3
 are made of a ferromagnetic, a paramagnetic and
a diamagnetic substance respectively. A magnet when brought close to
them will
(a) attract N
1
 and N
2
 strongly but repel N
3
Page 5


PART-I (Single Correct MCQs)
1. Two identical thin bar magnets each of length l
and pole strength m are placed at right angles to
each other, with north pole of one touching south
pole of the other, then the magnetic moment of
the system is
(a) 1 m l
(b) 2 m l
(c)  m l
(d) m l/2
2. If the period of oscillation of freely suspended bar magnet in earth’s
horizontal field H is 4 sec. When another magnet is brought near it, the
period of oscillation is reduced to 2s. The magnetic field of second bar
magnet is
(a) 4 H
(b) 3 H
(c) 2 H
(d) H
3. A coil in the shape of an equilateral triangle of side l is suspended between
the pole pieces of a permanent magnet such that  is in the 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)
(b)
(c)
(d)
4. A compass needle whose magnetic moment is 60 Am
2
, is directed
towards geographical north at any place experiencing moment of force
of 1.2 × 10
–3
 Nm. At that place the horizontal component of earth field
is 40 micro W/m
2
. What is the value of dip angle at that place?
(a) 30°
(b) 60°
(c) 45°
(d) 15°
5. The materials suitable for making electromagnets should have
(a) high retentivity and low coercivity
(b) low retentivity and low coercivity
(c) high retentivity and high coercivity
(d) low retentivity and high coercivity
6. The length of a magnet is large compared to its width and breadth. The
time period of its oscillation in a vibration magnetometer is 2s. The
magnet is cut along its length into three equal parts and these parts are
then placed on each other with their like poles together. The time period
of this combination will be
(a)
(b)
(c) 2 s
(d)
7. A magnetic dipole is under the influence of two magnetic fields The
angle between the field directions is 60° and one of the fields has a
magnitude of 1.2 × 10
–2
 T. If the dipole comes to stable equilibrium at
an angle of 15° with this field, what is the magnitude of other field ?
(a) 4.4 × 10
–3
 tesla
(b) 5.2 × 10
–3
 tesla
(c) 3.4 × 10
–3
 tesla
(d) 7.8 × 10
–3
 tesla
8. A bar magnet 8 cm long is placed in the magnetic merdian with the N-
pole pointing towards geographical north. Two netural points separated
by a distance of 6 cms are obtained on the equatorial axis of the magnet.
If horizontal component of earth’s field = 3.2 × 10
–5
 T, then pole strength
of magnet is
(a) 5 ab-amp × cm
(b) 10 ab-amp × cm
(c) 2.5 ab-amp × cm
(d) 20 ab-amp × cm
9. If the susceptibility of dia, para and ferro magnetic materials are ?
d
, ?
p
,
?
f
 respectively, then
(a) ?
d
 < ?
p
 < ?
f
(b) ?
d
 < ?
f
 < ?
p
(c) ?
f
 < ?
d
 < ?
p
(d) ?
f
 < ?
p
 < ?
d
10. The figure shows the various positions (labelled
by subscripts) of small magnetised needles P
and Q. The arrows show the direction of their
magnetic moment. Which configuration
corresponds to the lowest potential energy
among all the configurations shown ?
(a) PQ
3
(b) PQ
4
(c) PQ
5
(d) PQ
6
11. The angle of dip at a place is 37° and the vertical component of the
earth’s magnetic field is 6 × 10
–5
T. The earth’s magnetic field at this
place is (tan 37° = 3/4)
(a) 7 × 10
–5
 T
(b) 6 × 10
–5
 T
(c) 5 × 10
–5
 T
(d) 10
–4
 T
12. Needles N
1
, N
2
 and N
3
 are made of a ferromagnetic, a paramagnetic and
a diamagnetic substance respectively. A magnet when brought close to
them will
(a) attract N
1
 and N
2
 strongly but repel N
3
(b) attract N
1
 strongly, N
2
 weakly and repel N
3
 weakly
(c) attract N
1
 strongly, but repel N
2
 and N
3
 weakly
(d) attract all three of them
13. A vibration magnetometer consists of two identical bar magnets placed
one over the other such that they are perpendicular and bisect each other.
The time period of oscillation in a horizontal magnetic field is 2
5/4
seconds. One of the magnets is removed and if the other magnet
oscillates in the same field, then the time period in seconds is
(a) 2
1/4
(b) 2
1/2
(c) 2
(d) 2
3/4
14. Two identical bar magnets are fixed with their centres at a distance d
apart. A stationary charge Q is placed at P in between the gap of the
two magnets at a distance D from the centre O as shown in the Figure
The force on the charge Q is 
(a) directed perpendicular to the plane of paper
(b) zero
(c) directed along OP
(d) directed along PO
15. Two short bar magnets P and Q are arranged such that their centres are
on the X-axis and are separated by a large distance. The magnetic axes
of P and Q are along X and Y axes respectively.  At a point R, midway
between their centres, if B is the magnitude of induction due to Q, the
magnitude of total induction at R due to the both magnets is
(a) 3B