Practice Test - Magnetic effects & Magnetism Notes | EduRev

Created by: Vikas Sharma

: Practice Test - Magnetic effects & Magnetism Notes | EduRev

 Page 1


                                   [1] 
 
 
 
Test -04_Magnetic effects & Magnetism 
1. An iron rod of volume 10
-4
 m
3
 and relative 
permeability 1000 is placed inside a long solenoid 
wound with 5 turns/cm. If a current of 0.5 A is 
passed through the solenoid, then the magnetic 
moment of the rod is :    
(a) 10 Am
2
 (b) 15 Am
2
  
(c) 20 Am
2
 (d) 25 Am
2
 
2. For substances hystersis (B-H) curves are given as 
shown in figure. For making temporary magnet 
which of the following is best :  
 
 
3. The B-H curves (a) and (b) shown in the figure are 
associated with :  
(a) a diamagnetic and a 
paramagnetic substance 
respectively   
(b) a paramagnetic and a 
ferromagnetic substance  
respectively  
(c) soft iron and steel 
respectively   
(d) steel and soft iron respectively  
4. SI unit for measuring magnetic flux is called :  
(a) oersted  (b) maxwell   
(c) weber  (d) gauss  
5. The figure illustrate how B, 
the flux density inside  a 
sample of unmagnetised 
ferromagnetic material 
varies with B 0
 the magnetic 
flux density in which the 
sample is kept. For the 
sample to be suitable for making a permanent 
magnet,  
(a) OQ should be large, OR should be small  
(b) OQ and OR should both be large  
(c) OQ should be small and OR should be large  
(d) OQ and OR should both be small  
6. The variation of the intensity of magnetisation (I) 
with respect to the magnetising field (H) in a 
diamagnetic substance is described by the graph  
(a) OD 
  
(b) OC 
 
(c) OB 
(d) OA 
7. In figure , the magnetic induction B at the center 
O is  
(a) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(inwards) 
(b) 
R 4
I
0
µ
(inwards) 
(c) 
R 8
I
0
µ
(inwards) 
(d) 
R 2
I
R 8
I
0 0
p
µ
+
µ
(inwards) 
8. It is placed in a uniform 
magnetic field 
?
B ( out of paper) 
such that its plane is 
perpendicular to the direction 
of 
?
B . The wire will experience  
(a) No force  (b) A stretching force  
(c) A compressive force  (d) A torque  
9. In the figure , shown the magnetic induction at 
the centre of there are due to the current in will be  
 
 
 
 
(a) 
r
i
0
µ
 (b) 
r 2
i
0
µ
 
(c) 
r 4
i
0
µ
 (d) Zero  
10. A rod of a paramagnetic substance is placed in a 
non-uniform magnetic field. Which of the 
following figure shows its alignment in the field :  
 
Page 2


                                   [1] 
 
 
 
Test -04_Magnetic effects & Magnetism 
1. An iron rod of volume 10
-4
 m
3
 and relative 
permeability 1000 is placed inside a long solenoid 
wound with 5 turns/cm. If a current of 0.5 A is 
passed through the solenoid, then the magnetic 
moment of the rod is :    
(a) 10 Am
2
 (b) 15 Am
2
  
(c) 20 Am
2
 (d) 25 Am
2
 
2. For substances hystersis (B-H) curves are given as 
shown in figure. For making temporary magnet 
which of the following is best :  
 
 
3. The B-H curves (a) and (b) shown in the figure are 
associated with :  
(a) a diamagnetic and a 
paramagnetic substance 
respectively   
(b) a paramagnetic and a 
ferromagnetic substance  
respectively  
(c) soft iron and steel 
respectively   
(d) steel and soft iron respectively  
4. SI unit for measuring magnetic flux is called :  
(a) oersted  (b) maxwell   
(c) weber  (d) gauss  
5. The figure illustrate how B, 
the flux density inside  a 
sample of unmagnetised 
ferromagnetic material 
varies with B 0
 the magnetic 
flux density in which the 
sample is kept. For the 
sample to be suitable for making a permanent 
magnet,  
(a) OQ should be large, OR should be small  
(b) OQ and OR should both be large  
(c) OQ should be small and OR should be large  
(d) OQ and OR should both be small  
6. The variation of the intensity of magnetisation (I) 
with respect to the magnetising field (H) in a 
diamagnetic substance is described by the graph  
(a) OD 
  
(b) OC 
 
(c) OB 
(d) OA 
7. In figure , the magnetic induction B at the center 
O is  
(a) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(inwards) 
(b) 
R 4
I
0
µ
(inwards) 
(c) 
R 8
I
0
µ
(inwards) 
(d) 
R 2
I
R 8
I
0 0
p
µ
+
µ
(inwards) 
8. It is placed in a uniform 
magnetic field 
?
B ( out of paper) 
such that its plane is 
perpendicular to the direction 
of 
?
B . The wire will experience  
(a) No force  (b) A stretching force  
(c) A compressive force  (d) A torque  
9. In the figure , shown the magnetic induction at 
the centre of there are due to the current in will be  
 
 
 
 
(a) 
r
i
0
µ
 (b) 
r 2
i
0
µ
 
(c) 
r 4
i
0
µ
 (d) Zero  
10. A rod of a paramagnetic substance is placed in a 
non-uniform magnetic field. Which of the 
following figure shows its alignment in the field :  
 
                                   [2] 
 
 
 
11. The variation of magnetic susceptibility ( ?) with 
magnetizing field for a paramagnetic substance is    
 
12. The ratio of magnetic moments of two short 
magnets which gives null deflection in tan B 
position at 12 cm and 18 cm from the centre of a 
deflection magnetometer is :  
(a) 2 : 3  (b) 8 : 27   
(c) 27 : 8  (d) 4 : 9  
13. The net magnetic 
moment of two identical 
magnets each of 
magnetic moment M 0
, 
inclined at 60 ° with each 
other is :  
 (a) M
0
  
(b) 2 M
0
  
(c) 3 M
0
  
(d) 2M
0
 
14. The S.I. unit of magnetic dipole moment is   
(a) AM
–1 
(b) AM
2
 
(c) TMA
–1 
(d) TMA
–2
 
15. Curie’s law can be written as  
(a) ? ?(T–T
C
) (b) ? ?
C
T T
1
-
 
(c) ? ?
T
1
  (d) ? ?T 
16. In the above problem, if the straight wires are 
turned upwards as shown in fig, then the value of 
B at the centre O is given by  
(a) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(inwards) 
(b) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(outwards) 
(c) 
R 2
I
R 4
I
0 0
p
µ
+
µ
(outwards) 
(d) 
R 4
I
0
µ
(inwards) 
 
 
17. A and B are two concentric circular conductors of 
centre O and current I
1
 and I
2
 
as shown in the adjacent 
figure. It ratio of the flux 
densities at O due to A and B 
is 1 : 3, then the value of I
1
 /I
2
 
is  
 
(a) 
6
1
 (b) 
4
1
 
(c) 
3
1
 (d) 
2
1
 
18. A current i is flowing a loop of 
radius r as shown in the figure. 
The magnetic induction 
intensity at the centre O will be  
 
(a) 
r 4
i
0
p
µ
? (b) 
2
0
r 4
sin i 2
p
? µ
   
(c) 
r 2
sin i 2
0
? µ
 (d) 
r 4
sin i
0
? µ
  
19. If f
1
 and f
2
 be the angles of dip observed in two 
vertical planes at right angles to each other and f 
be the true angle of dip, then :  
(a) cos
2
 f = cos
2
f
1
 + cos
2
f
2
  
(b) sec f = sec
2
f
1
 + sec
2
f
2
  
(c) tan
2
 f = tan
2
f
1
 + tan
2
f
2
  
(d) cot
2
 f = cot
2
f
1
 + cot
2
f
2
 
20. A rod of a diamagnetic material is placed in a 
non-uniform strong magnetic field. Which of the 
figure below shows the alignment of the rod in 
the field :   
 
21. If the symbols have their usual meanings, the 
expression 
MH
I
has the dimensions of :  
(a) frequency  (b) time   
(c) distance  (d) None of these  
 
22. Which of the following is most suitable for the 
core of the electromagnets  :  
(a) Air  (b) Steel   
(c) Soft iron  (d) Cu-Ni alloy  
Page 3


                                   [1] 
 
 
 
Test -04_Magnetic effects & Magnetism 
1. An iron rod of volume 10
-4
 m
3
 and relative 
permeability 1000 is placed inside a long solenoid 
wound with 5 turns/cm. If a current of 0.5 A is 
passed through the solenoid, then the magnetic 
moment of the rod is :    
(a) 10 Am
2
 (b) 15 Am
2
  
(c) 20 Am
2
 (d) 25 Am
2
 
2. For substances hystersis (B-H) curves are given as 
shown in figure. For making temporary magnet 
which of the following is best :  
 
 
3. The B-H curves (a) and (b) shown in the figure are 
associated with :  
(a) a diamagnetic and a 
paramagnetic substance 
respectively   
(b) a paramagnetic and a 
ferromagnetic substance  
respectively  
(c) soft iron and steel 
respectively   
(d) steel and soft iron respectively  
4. SI unit for measuring magnetic flux is called :  
(a) oersted  (b) maxwell   
(c) weber  (d) gauss  
5. The figure illustrate how B, 
the flux density inside  a 
sample of unmagnetised 
ferromagnetic material 
varies with B 0
 the magnetic 
flux density in which the 
sample is kept. For the 
sample to be suitable for making a permanent 
magnet,  
(a) OQ should be large, OR should be small  
(b) OQ and OR should both be large  
(c) OQ should be small and OR should be large  
(d) OQ and OR should both be small  
6. The variation of the intensity of magnetisation (I) 
with respect to the magnetising field (H) in a 
diamagnetic substance is described by the graph  
(a) OD 
  
(b) OC 
 
(c) OB 
(d) OA 
7. In figure , the magnetic induction B at the center 
O is  
(a) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(inwards) 
(b) 
R 4
I
0
µ
(inwards) 
(c) 
R 8
I
0
µ
(inwards) 
(d) 
R 2
I
R 8
I
0 0
p
µ
+
µ
(inwards) 
8. It is placed in a uniform 
magnetic field 
?
B ( out of paper) 
such that its plane is 
perpendicular to the direction 
of 
?
B . The wire will experience  
(a) No force  (b) A stretching force  
(c) A compressive force  (d) A torque  
9. In the figure , shown the magnetic induction at 
the centre of there are due to the current in will be  
 
 
 
 
(a) 
r
i
0
µ
 (b) 
r 2
i
0
µ
 
(c) 
r 4
i
0
µ
 (d) Zero  
10. A rod of a paramagnetic substance is placed in a 
non-uniform magnetic field. Which of the 
following figure shows its alignment in the field :  
 
                                   [2] 
 
 
 
11. The variation of magnetic susceptibility ( ?) with 
magnetizing field for a paramagnetic substance is    
 
12. The ratio of magnetic moments of two short 
magnets which gives null deflection in tan B 
position at 12 cm and 18 cm from the centre of a 
deflection magnetometer is :  
(a) 2 : 3  (b) 8 : 27   
(c) 27 : 8  (d) 4 : 9  
13. The net magnetic 
moment of two identical 
magnets each of 
magnetic moment M 0
, 
inclined at 60 ° with each 
other is :  
 (a) M
0
  
(b) 2 M
0
  
(c) 3 M
0
  
(d) 2M
0
 
14. The S.I. unit of magnetic dipole moment is   
(a) AM
–1 
(b) AM
2
 
(c) TMA
–1 
(d) TMA
–2
 
15. Curie’s law can be written as  
(a) ? ?(T–T
C
) (b) ? ?
C
T T
1
-
 
(c) ? ?
T
1
  (d) ? ?T 
16. In the above problem, if the straight wires are 
turned upwards as shown in fig, then the value of 
B at the centre O is given by  
(a) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(inwards) 
(b) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(outwards) 
(c) 
R 2
I
R 4
I
0 0
p
µ
+
µ
(outwards) 
(d) 
R 4
I
0
µ
(inwards) 
 
 
17. A and B are two concentric circular conductors of 
centre O and current I
1
 and I
2
 
as shown in the adjacent 
figure. It ratio of the flux 
densities at O due to A and B 
is 1 : 3, then the value of I
1
 /I
2
 
is  
 
(a) 
6
1
 (b) 
4
1
 
(c) 
3
1
 (d) 
2
1
 
18. A current i is flowing a loop of 
radius r as shown in the figure. 
The magnetic induction 
intensity at the centre O will be  
 
(a) 
r 4
i
0
p
µ
? (b) 
2
0
r 4
sin i 2
p
? µ
   
(c) 
r 2
sin i 2
0
? µ
 (d) 
r 4
sin i
0
? µ
  
19. If f
1
 and f
2
 be the angles of dip observed in two 
vertical planes at right angles to each other and f 
be the true angle of dip, then :  
(a) cos
2
 f = cos
2
f
1
 + cos
2
f
2
  
(b) sec f = sec
2
f
1
 + sec
2
f
2
  
(c) tan
2
 f = tan
2
f
1
 + tan
2
f
2
  
(d) cot
2
 f = cot
2
f
1
 + cot
2
f
2
 
20. A rod of a diamagnetic material is placed in a 
non-uniform strong magnetic field. Which of the 
figure below shows the alignment of the rod in 
the field :   
 
21. If the symbols have their usual meanings, the 
expression 
MH
I
has the dimensions of :  
(a) frequency  (b) time   
(c) distance  (d) None of these  
 
22. Which of the following is most suitable for the 
core of the electromagnets  :  
(a) Air  (b) Steel   
(c) Soft iron  (d) Cu-Ni alloy  
                                   [3] 
 
 
 
23. The ratio of SI unit to C.G.S. unit for magnetic flux 
density is :  
(a) 10
3
 (b) 10
4
   
(c) 10
-4
 (d) 10
-3
 
24. Identify the paramagnetic substance  
(a) Iron  (b) Aluminium  
(c) Nickel  (d) Hydrogen  
25. A frog can be deviated in a magnetic field 
produced by a current in a vertical solenoid 
placed below the frog. This is possible because the 
body of the frog behaves as   
(a) Paramagnetic   
(b) Diamagnetic  
(c) Ferromagnetic   
(d) Antiferromagnetic 
In every question a statement of ASSERTION is 
followed by a statement of REASON. Mark the 
correct answer out of the following choices:  
(a) If both ASSERTION and REASON are true 
and reason is the correct explanation of the 
assertion. 
(b) If both ASSERTION and REASON are true 
but reason is not the correct explanation of the 
assertion. 
(c) If ASSERTION is true but REASON is false. 
(d) If ASSERTION is false but REASON is true. 
26. Assertion: When a magnet of length L and 
magnetic moment M is bent to form a 
semicircular arc, the new magnetic moment is 
2M/ p. 
Reason: Magnetic moment of a magnet depends 
only upon the distance between the poles of the 
magnet.  
27. Assertion: An iron nail placed in the magnetic 
field of a bar magnet experiences a torque as well 
as a force. 
Reason: The magnetic field near a bar magnet is 
non-uniform  
28. Assertion: Ferromagnetic substances do not obey 
Curies law. 
Reason:  Above the Curie temperature, a 
ferromagnetic substance shows paramagnetic 
properties. 
29. Assertion: Copper is diamagnetic but copper 
chloride is attracted by magnetic fields.  
Reason: Copper chloride is paramagnetic.  
30. Assertion: A liquid contained in one limb of a 
narrow U-tube is placed between the pole pieces 
of an electromagnet, with the meniscus in line 
with the field as shown. On switching on the 
electromagnet the level in the limb goes up 
slightly.  
 
Reason: The liquid is paramagnetic.  
 
 
 
ANSWER KEY 
 
1 d 6 B 11 A 16 D 21 B 26 C 
2 d 7 C 12 B 17 A                                                                                                                                                                                              22 C 27 A 
3 C 8 B 13 C 18 A 23 B 28 B 
4 C 9 C 14 B 19 D 24 D 29 A 
5 B 10 A 15 
C 
20 D 25 B 30 A 
 
 
SOLUTIONS 
1. Use M= NIA 
2. For a temporary  magnet the hystersis loop  should  be long and narrow. 
3. (c) 
4. 1 Wb = 1 Tm
2
 
5. In the given figure OQ refers to retentivity while OR refers to corecivity should be high. 
6. Intensity of magnetization of diamagnetic substance is very small and negative. 
Page 4


                                   [1] 
 
 
 
Test -04_Magnetic effects & Magnetism 
1. An iron rod of volume 10
-4
 m
3
 and relative 
permeability 1000 is placed inside a long solenoid 
wound with 5 turns/cm. If a current of 0.5 A is 
passed through the solenoid, then the magnetic 
moment of the rod is :    
(a) 10 Am
2
 (b) 15 Am
2
  
(c) 20 Am
2
 (d) 25 Am
2
 
2. For substances hystersis (B-H) curves are given as 
shown in figure. For making temporary magnet 
which of the following is best :  
 
 
3. The B-H curves (a) and (b) shown in the figure are 
associated with :  
(a) a diamagnetic and a 
paramagnetic substance 
respectively   
(b) a paramagnetic and a 
ferromagnetic substance  
respectively  
(c) soft iron and steel 
respectively   
(d) steel and soft iron respectively  
4. SI unit for measuring magnetic flux is called :  
(a) oersted  (b) maxwell   
(c) weber  (d) gauss  
5. The figure illustrate how B, 
the flux density inside  a 
sample of unmagnetised 
ferromagnetic material 
varies with B 0
 the magnetic 
flux density in which the 
sample is kept. For the 
sample to be suitable for making a permanent 
magnet,  
(a) OQ should be large, OR should be small  
(b) OQ and OR should both be large  
(c) OQ should be small and OR should be large  
(d) OQ and OR should both be small  
6. The variation of the intensity of magnetisation (I) 
with respect to the magnetising field (H) in a 
diamagnetic substance is described by the graph  
(a) OD 
  
(b) OC 
 
(c) OB 
(d) OA 
7. In figure , the magnetic induction B at the center 
O is  
(a) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(inwards) 
(b) 
R 4
I
0
µ
(inwards) 
(c) 
R 8
I
0
µ
(inwards) 
(d) 
R 2
I
R 8
I
0 0
p
µ
+
µ
(inwards) 
8. It is placed in a uniform 
magnetic field 
?
B ( out of paper) 
such that its plane is 
perpendicular to the direction 
of 
?
B . The wire will experience  
(a) No force  (b) A stretching force  
(c) A compressive force  (d) A torque  
9. In the figure , shown the magnetic induction at 
the centre of there are due to the current in will be  
 
 
 
 
(a) 
r
i
0
µ
 (b) 
r 2
i
0
µ
 
(c) 
r 4
i
0
µ
 (d) Zero  
10. A rod of a paramagnetic substance is placed in a 
non-uniform magnetic field. Which of the 
following figure shows its alignment in the field :  
 
                                   [2] 
 
 
 
11. The variation of magnetic susceptibility ( ?) with 
magnetizing field for a paramagnetic substance is    
 
12. The ratio of magnetic moments of two short 
magnets which gives null deflection in tan B 
position at 12 cm and 18 cm from the centre of a 
deflection magnetometer is :  
(a) 2 : 3  (b) 8 : 27   
(c) 27 : 8  (d) 4 : 9  
13. The net magnetic 
moment of two identical 
magnets each of 
magnetic moment M 0
, 
inclined at 60 ° with each 
other is :  
 (a) M
0
  
(b) 2 M
0
  
(c) 3 M
0
  
(d) 2M
0
 
14. The S.I. unit of magnetic dipole moment is   
(a) AM
–1 
(b) AM
2
 
(c) TMA
–1 
(d) TMA
–2
 
15. Curie’s law can be written as  
(a) ? ?(T–T
C
) (b) ? ?
C
T T
1
-
 
(c) ? ?
T
1
  (d) ? ?T 
16. In the above problem, if the straight wires are 
turned upwards as shown in fig, then the value of 
B at the centre O is given by  
(a) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(inwards) 
(b) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(outwards) 
(c) 
R 2
I
R 4
I
0 0
p
µ
+
µ
(outwards) 
(d) 
R 4
I
0
µ
(inwards) 
 
 
17. A and B are two concentric circular conductors of 
centre O and current I
1
 and I
2
 
as shown in the adjacent 
figure. It ratio of the flux 
densities at O due to A and B 
is 1 : 3, then the value of I
1
 /I
2
 
is  
 
(a) 
6
1
 (b) 
4
1
 
(c) 
3
1
 (d) 
2
1
 
18. A current i is flowing a loop of 
radius r as shown in the figure. 
The magnetic induction 
intensity at the centre O will be  
 
(a) 
r 4
i
0
p
µ
? (b) 
2
0
r 4
sin i 2
p
? µ
   
(c) 
r 2
sin i 2
0
? µ
 (d) 
r 4
sin i
0
? µ
  
19. If f
1
 and f
2
 be the angles of dip observed in two 
vertical planes at right angles to each other and f 
be the true angle of dip, then :  
(a) cos
2
 f = cos
2
f
1
 + cos
2
f
2
  
(b) sec f = sec
2
f
1
 + sec
2
f
2
  
(c) tan
2
 f = tan
2
f
1
 + tan
2
f
2
  
(d) cot
2
 f = cot
2
f
1
 + cot
2
f
2
 
20. A rod of a diamagnetic material is placed in a 
non-uniform strong magnetic field. Which of the 
figure below shows the alignment of the rod in 
the field :   
 
21. If the symbols have their usual meanings, the 
expression 
MH
I
has the dimensions of :  
(a) frequency  (b) time   
(c) distance  (d) None of these  
 
22. Which of the following is most suitable for the 
core of the electromagnets  :  
(a) Air  (b) Steel   
(c) Soft iron  (d) Cu-Ni alloy  
                                   [3] 
 
 
 
23. The ratio of SI unit to C.G.S. unit for magnetic flux 
density is :  
(a) 10
3
 (b) 10
4
   
(c) 10
-4
 (d) 10
-3
 
24. Identify the paramagnetic substance  
(a) Iron  (b) Aluminium  
(c) Nickel  (d) Hydrogen  
25. A frog can be deviated in a magnetic field 
produced by a current in a vertical solenoid 
placed below the frog. This is possible because the 
body of the frog behaves as   
(a) Paramagnetic   
(b) Diamagnetic  
(c) Ferromagnetic   
(d) Antiferromagnetic 
In every question a statement of ASSERTION is 
followed by a statement of REASON. Mark the 
correct answer out of the following choices:  
(a) If both ASSERTION and REASON are true 
and reason is the correct explanation of the 
assertion. 
(b) If both ASSERTION and REASON are true 
but reason is not the correct explanation of the 
assertion. 
(c) If ASSERTION is true but REASON is false. 
(d) If ASSERTION is false but REASON is true. 
26. Assertion: When a magnet of length L and 
magnetic moment M is bent to form a 
semicircular arc, the new magnetic moment is 
2M/ p. 
Reason: Magnetic moment of a magnet depends 
only upon the distance between the poles of the 
magnet.  
27. Assertion: An iron nail placed in the magnetic 
field of a bar magnet experiences a torque as well 
as a force. 
Reason: The magnetic field near a bar magnet is 
non-uniform  
28. Assertion: Ferromagnetic substances do not obey 
Curies law. 
Reason:  Above the Curie temperature, a 
ferromagnetic substance shows paramagnetic 
properties. 
29. Assertion: Copper is diamagnetic but copper 
chloride is attracted by magnetic fields.  
Reason: Copper chloride is paramagnetic.  
30. Assertion: A liquid contained in one limb of a 
narrow U-tube is placed between the pole pieces 
of an electromagnet, with the meniscus in line 
with the field as shown. On switching on the 
electromagnet the level in the limb goes up 
slightly.  
 
Reason: The liquid is paramagnetic.  
 
 
 
ANSWER KEY 
 
1 d 6 B 11 A 16 D 21 B 26 C 
2 d 7 C 12 B 17 A                                                                                                                                                                                              22 C 27 A 
3 C 8 B 13 C 18 A 23 B 28 B 
4 C 9 C 14 B 19 D 24 D 29 A 
5 B 10 A 15 
C 
20 D 25 B 30 A 
 
 
SOLUTIONS 
1. Use M= NIA 
2. For a temporary  magnet the hystersis loop  should  be long and narrow. 
3. (c) 
4. 1 Wb = 1 Tm
2
 
5. In the given figure OQ refers to retentivity while OR refers to corecivity should be high. 
6. Intensity of magnetization of diamagnetic substance is very small and negative. 
                                   [4] 
 
 
 
7. 
?
?
?
?
?
?
? µ
0
0
36 r 2
I
= 
?
?
?
?
?
?
µ
0
0
36
90
r 2
I
=
r 8
I
0
µ
 
8. (B) 
9. (C) 
10. When a paramagnetic substance is placed in a non- uniform magnetic field, then substance always aligns 
along the filed lines, because by aligning along the lines  of induction, magnetization is maximum 
11. Susceptibility of a paramagnetic substance is independent  of magnetizing field. 
12. 
3
2
2
3
1
1
d
M
d
M
=   ?   
27
8
3
2
d
d
M
M
3
3
2
1
2
1
=
?
?
?
?
?
?
=
?
?
?
?
?
?
?
?
=  
13. (c) 
14. (B) 
15. (C) 
16. The contribution of semi -circular wire is 
R 4
I
0
µ
 The two semi -infinite wires become one completely infinite 
wire, thus the contribution of straight wires is 
R 4
I
0
p
µ
 The direction of B is inwards ?. Hence, B = 
R 2
I
R 4
I
0 0
p
µ
-
µ
 
17. r
1
 : r
2
 = 1 : 2 and B
1
 : B
2
 = 1 : 3  We know that  B = 
r 2
ni
0
µ
 ?  
6
1
2 3
1 1
r B
r B
i
i
2 2
1 1
2
1
=
×
×
= = 
18. In this case, 2 p = ?  Hence, from the formula B = 
r
pi 2
.
4
0
p
µ
 we get  B = 
r
i
.
4
0
?
p
µ
 
19. Let a  be the angle which one of the planes make  with the magnetic meridian the other plane  makes  an angle 
(90
o
– a) with it. The component of H in these planes will  be H cos a and H sin a  respectively. If f
1
 and f
2
  are 
the apparent dips in these two planes, then  
tan f
1
 = 
a cos H
V
  i.e  cos a = 
1
tan H
V
f
….(i)  tan f
2
  = 
a sin H
V
 
i.e sin a  = 
2
tan H
V
f
….(ii)  Squaring and adding  equation (i) and (ii), we get  
cos
2 
a + sin
2
 a = 
2
H
V
?
?
?
?
?
?
 
?
?
?
?
?
?
?
?
f
=
f
2
2 2
tan
1
tan
1
  i.e. 1 = ) cot (cot
H
V
2
2
1
2
2
2
f + f or 
2
2
1
2
2
2
cot cot
V
H
f + f = i.e. cot
2 
 
cot
2
f = cot
2
 f
1
 + cot
2
 f
2   
This  is the required  result.  
20. When a diamagnetic substance is placed in a non -uniform strong magnetic field, it always aligns itself 
perpendicular to the lines of induction, hence repulsion. Magnetisation, hence susceptibility is negative. 
21. (B) 
22. Soft iron has highest susceptibility.  
23. Magnetic flux density is the magnetic field.   1 T = 10
4
 G  ?  
4
10
G 1
T 1
= 
24. (D) 
25. Diamagnetic substance are repelled by the magnetic field. 
26. (c) Assertion is true but reason is false 
Consider a magnet of length L and pole strength m. Its magnetic moment = mL 
Next bend it into a semicircular are of radius R. 
Then R = 
p
L
and the magnetic moment M
1
 = m 2 R = .
M 2 L m 2
p
=
p
 
The assertion is true. The magnetic moment which depends upon the pole strength and the distance between 
the poles is calculated as 
p
M 2
. The reason is false. It is not only the distance between the poles but also the 
pole strength which determines the magnetic moment. 
27. (a) The reason is the correct explanation of the assertion and both are correct. 
Any magnet placed in a non-uniform magnetic field experiences both a net force as well as a torque. The 
magnetic field around a bar magnet is non-uniform. An iron nail placed in a magnetic field acquires induced 
90
o
 – a 
H
1
= H cos a 
H 
H
2
 = H sin a 
Page 5


                                   [1] 
 
 
 
Test -04_Magnetic effects & Magnetism 
1. An iron rod of volume 10
-4
 m
3
 and relative 
permeability 1000 is placed inside a long solenoid 
wound with 5 turns/cm. If a current of 0.5 A is 
passed through the solenoid, then the magnetic 
moment of the rod is :    
(a) 10 Am
2
 (b) 15 Am
2
  
(c) 20 Am
2
 (d) 25 Am
2
 
2. For substances hystersis (B-H) curves are given as 
shown in figure. For making temporary magnet 
which of the following is best :  
 
 
3. The B-H curves (a) and (b) shown in the figure are 
associated with :  
(a) a diamagnetic and a 
paramagnetic substance 
respectively   
(b) a paramagnetic and a 
ferromagnetic substance  
respectively  
(c) soft iron and steel 
respectively   
(d) steel and soft iron respectively  
4. SI unit for measuring magnetic flux is called :  
(a) oersted  (b) maxwell   
(c) weber  (d) gauss  
5. The figure illustrate how B, 
the flux density inside  a 
sample of unmagnetised 
ferromagnetic material 
varies with B 0
 the magnetic 
flux density in which the 
sample is kept. For the 
sample to be suitable for making a permanent 
magnet,  
(a) OQ should be large, OR should be small  
(b) OQ and OR should both be large  
(c) OQ should be small and OR should be large  
(d) OQ and OR should both be small  
6. The variation of the intensity of magnetisation (I) 
with respect to the magnetising field (H) in a 
diamagnetic substance is described by the graph  
(a) OD 
  
(b) OC 
 
(c) OB 
(d) OA 
7. In figure , the magnetic induction B at the center 
O is  
(a) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(inwards) 
(b) 
R 4
I
0
µ
(inwards) 
(c) 
R 8
I
0
µ
(inwards) 
(d) 
R 2
I
R 8
I
0 0
p
µ
+
µ
(inwards) 
8. It is placed in a uniform 
magnetic field 
?
B ( out of paper) 
such that its plane is 
perpendicular to the direction 
of 
?
B . The wire will experience  
(a) No force  (b) A stretching force  
(c) A compressive force  (d) A torque  
9. In the figure , shown the magnetic induction at 
the centre of there are due to the current in will be  
 
 
 
 
(a) 
r
i
0
µ
 (b) 
r 2
i
0
µ
 
(c) 
r 4
i
0
µ
 (d) Zero  
10. A rod of a paramagnetic substance is placed in a 
non-uniform magnetic field. Which of the 
following figure shows its alignment in the field :  
 
                                   [2] 
 
 
 
11. The variation of magnetic susceptibility ( ?) with 
magnetizing field for a paramagnetic substance is    
 
12. The ratio of magnetic moments of two short 
magnets which gives null deflection in tan B 
position at 12 cm and 18 cm from the centre of a 
deflection magnetometer is :  
(a) 2 : 3  (b) 8 : 27   
(c) 27 : 8  (d) 4 : 9  
13. The net magnetic 
moment of two identical 
magnets each of 
magnetic moment M 0
, 
inclined at 60 ° with each 
other is :  
 (a) M
0
  
(b) 2 M
0
  
(c) 3 M
0
  
(d) 2M
0
 
14. The S.I. unit of magnetic dipole moment is   
(a) AM
–1 
(b) AM
2
 
(c) TMA
–1 
(d) TMA
–2
 
15. Curie’s law can be written as  
(a) ? ?(T–T
C
) (b) ? ?
C
T T
1
-
 
(c) ? ?
T
1
  (d) ? ?T 
16. In the above problem, if the straight wires are 
turned upwards as shown in fig, then the value of 
B at the centre O is given by  
(a) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(inwards) 
(b) 
R 2
I
R 4
I
0 0
p
µ
-
µ
(outwards) 
(c) 
R 2
I
R 4
I
0 0
p
µ
+
µ
(outwards) 
(d) 
R 4
I
0
µ
(inwards) 
 
 
17. A and B are two concentric circular conductors of 
centre O and current I
1
 and I
2
 
as shown in the adjacent 
figure. It ratio of the flux 
densities at O due to A and B 
is 1 : 3, then the value of I
1
 /I
2
 
is  
 
(a) 
6
1
 (b) 
4
1
 
(c) 
3
1
 (d) 
2
1
 
18. A current i is flowing a loop of 
radius r as shown in the figure. 
The magnetic induction 
intensity at the centre O will be  
 
(a) 
r 4
i
0
p
µ
? (b) 
2
0
r 4
sin i 2
p
? µ
   
(c) 
r 2
sin i 2
0
? µ
 (d) 
r 4
sin i
0
? µ
  
19. If f
1
 and f
2
 be the angles of dip observed in two 
vertical planes at right angles to each other and f 
be the true angle of dip, then :  
(a) cos
2
 f = cos
2
f
1
 + cos
2
f
2
  
(b) sec f = sec
2
f
1
 + sec
2
f
2
  
(c) tan
2
 f = tan
2
f
1
 + tan
2
f
2
  
(d) cot
2
 f = cot
2
f
1
 + cot
2
f
2
 
20. A rod of a diamagnetic material is placed in a 
non-uniform strong magnetic field. Which of the 
figure below shows the alignment of the rod in 
the field :   
 
21. If the symbols have their usual meanings, the 
expression 
MH
I
has the dimensions of :  
(a) frequency  (b) time   
(c) distance  (d) None of these  
 
22. Which of the following is most suitable for the 
core of the electromagnets  :  
(a) Air  (b) Steel   
(c) Soft iron  (d) Cu-Ni alloy  
                                   [3] 
 
 
 
23. The ratio of SI unit to C.G.S. unit for magnetic flux 
density is :  
(a) 10
3
 (b) 10
4
   
(c) 10
-4
 (d) 10
-3
 
24. Identify the paramagnetic substance  
(a) Iron  (b) Aluminium  
(c) Nickel  (d) Hydrogen  
25. A frog can be deviated in a magnetic field 
produced by a current in a vertical solenoid 
placed below the frog. This is possible because the 
body of the frog behaves as   
(a) Paramagnetic   
(b) Diamagnetic  
(c) Ferromagnetic   
(d) Antiferromagnetic 
In every question a statement of ASSERTION is 
followed by a statement of REASON. Mark the 
correct answer out of the following choices:  
(a) If both ASSERTION and REASON are true 
and reason is the correct explanation of the 
assertion. 
(b) If both ASSERTION and REASON are true 
but reason is not the correct explanation of the 
assertion. 
(c) If ASSERTION is true but REASON is false. 
(d) If ASSERTION is false but REASON is true. 
26. Assertion: When a magnet of length L and 
magnetic moment M is bent to form a 
semicircular arc, the new magnetic moment is 
2M/ p. 
Reason: Magnetic moment of a magnet depends 
only upon the distance between the poles of the 
magnet.  
27. Assertion: An iron nail placed in the magnetic 
field of a bar magnet experiences a torque as well 
as a force. 
Reason: The magnetic field near a bar magnet is 
non-uniform  
28. Assertion: Ferromagnetic substances do not obey 
Curies law. 
Reason:  Above the Curie temperature, a 
ferromagnetic substance shows paramagnetic 
properties. 
29. Assertion: Copper is diamagnetic but copper 
chloride is attracted by magnetic fields.  
Reason: Copper chloride is paramagnetic.  
30. Assertion: A liquid contained in one limb of a 
narrow U-tube is placed between the pole pieces 
of an electromagnet, with the meniscus in line 
with the field as shown. On switching on the 
electromagnet the level in the limb goes up 
slightly.  
 
Reason: The liquid is paramagnetic.  
 
 
 
ANSWER KEY 
 
1 d 6 B 11 A 16 D 21 B 26 C 
2 d 7 C 12 B 17 A                                                                                                                                                                                              22 C 27 A 
3 C 8 B 13 C 18 A 23 B 28 B 
4 C 9 C 14 B 19 D 24 D 29 A 
5 B 10 A 15 
C 
20 D 25 B 30 A 
 
 
SOLUTIONS 
1. Use M= NIA 
2. For a temporary  magnet the hystersis loop  should  be long and narrow. 
3. (c) 
4. 1 Wb = 1 Tm
2
 
5. In the given figure OQ refers to retentivity while OR refers to corecivity should be high. 
6. Intensity of magnetization of diamagnetic substance is very small and negative. 
                                   [4] 
 
 
 
7. 
?
?
?
?
?
?
? µ
0
0
36 r 2
I
= 
?
?
?
?
?
?
µ
0
0
36
90
r 2
I
=
r 8
I
0
µ
 
8. (B) 
9. (C) 
10. When a paramagnetic substance is placed in a non- uniform magnetic field, then substance always aligns 
along the filed lines, because by aligning along the lines  of induction, magnetization is maximum 
11. Susceptibility of a paramagnetic substance is independent  of magnetizing field. 
12. 
3
2
2
3
1
1
d
M
d
M
=   ?   
27
8
3
2
d
d
M
M
3
3
2
1
2
1
=
?
?
?
?
?
?
=
?
?
?
?
?
?
?
?
=  
13. (c) 
14. (B) 
15. (C) 
16. The contribution of semi -circular wire is 
R 4
I
0
µ
 The two semi -infinite wires become one completely infinite 
wire, thus the contribution of straight wires is 
R 4
I
0
p
µ
 The direction of B is inwards ?. Hence, B = 
R 2
I
R 4
I
0 0
p
µ
-
µ
 
17. r
1
 : r
2
 = 1 : 2 and B
1
 : B
2
 = 1 : 3  We know that  B = 
r 2
ni
0
µ
 ?  
6
1
2 3
1 1
r B
r B
i
i
2 2
1 1
2
1
=
×
×
= = 
18. In this case, 2 p = ?  Hence, from the formula B = 
r
pi 2
.
4
0
p
µ
 we get  B = 
r
i
.
4
0
?
p
µ
 
19. Let a  be the angle which one of the planes make  with the magnetic meridian the other plane  makes  an angle 
(90
o
– a) with it. The component of H in these planes will  be H cos a and H sin a  respectively. If f
1
 and f
2
  are 
the apparent dips in these two planes, then  
tan f
1
 = 
a cos H
V
  i.e  cos a = 
1
tan H
V
f
….(i)  tan f
2
  = 
a sin H
V
 
i.e sin a  = 
2
tan H
V
f
….(ii)  Squaring and adding  equation (i) and (ii), we get  
cos
2 
a + sin
2
 a = 
2
H
V
?
?
?
?
?
?
 
?
?
?
?
?
?
?
?
f
=
f
2
2 2
tan
1
tan
1
  i.e. 1 = ) cot (cot
H
V
2
2
1
2
2
2
f + f or 
2
2
1
2
2
2
cot cot
V
H
f + f = i.e. cot
2 
 
cot
2
f = cot
2
 f
1
 + cot
2
 f
2   
This  is the required  result.  
20. When a diamagnetic substance is placed in a non -uniform strong magnetic field, it always aligns itself 
perpendicular to the lines of induction, hence repulsion. Magnetisation, hence susceptibility is negative. 
21. (B) 
22. Soft iron has highest susceptibility.  
23. Magnetic flux density is the magnetic field.   1 T = 10
4
 G  ?  
4
10
G 1
T 1
= 
24. (D) 
25. Diamagnetic substance are repelled by the magnetic field. 
26. (c) Assertion is true but reason is false 
Consider a magnet of length L and pole strength m. Its magnetic moment = mL 
Next bend it into a semicircular are of radius R. 
Then R = 
p
L
and the magnetic moment M
1
 = m 2 R = .
M 2 L m 2
p
=
p
 
The assertion is true. The magnetic moment which depends upon the pole strength and the distance between 
the poles is calculated as 
p
M 2
. The reason is false. It is not only the distance between the poles but also the 
pole strength which determines the magnetic moment. 
27. (a) The reason is the correct explanation of the assertion and both are correct. 
Any magnet placed in a non-uniform magnetic field experiences both a net force as well as a torque. The 
magnetic field around a bar magnet is non-uniform. An iron nail placed in a magnetic field acquires induced 
90
o
 – a 
H
1
= H cos a 
H 
H
2
 = H sin a 
                                   [5] 
 
 
 
magnetization. Thus the iron nail experiences a torque as well as a force when placed in the non-uniform 
magnetic field of a bar magnet. 
28. (b) Both the assertion and reason are correct independent statements. 
Till a certain temperature the susceptibility of ferromagnetic substances do not follow the variation given by 
Curie’s law. At a critical temperature called Curie’s temperature the material loses its ferromagnetic properties 
and becomes paramagnetic. Above this temperature the variation of susceptibility is according to Curie’s law. 
29. (a) The reason is true. It explains the assertion which is also true. 
Copper is diamagnetic. It is not necessary that all compounds or alloys of copper will also be diamagnetic. As 
copper chloride is paramagnetic it will be attracted by strong magnetic fields. 
30. (a) The reason is true. It explains the assertion which is also true. 
Both paramagnetic and ferromagnetic substances are attracted by magnetic fields. However, the force of 
attraction is weak for paramagnetic substances and very strong for ferromagnetic substances. When the 
electromagnet is switched ON, the magnetic field attracts more of the liquid and the level rises. For a 
paramagnetic liquid, the force being less the level rises only by a slight amount. The assertion is correct based 
on the information in the reason. 
 
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