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Magnetism and Matter
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JEE Mains Questions
Magnetism And Matter
Physics
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A magnetic dipole in a constant magnetic field has ;
A
Minimum potential energy when the torque is maximum.
B
Zero potential energy when the torque is minimum.
C
Zero potential energy when the torque is maximum.
D
Maximum potential energy when the torque is maximum.
Medium
JEE Mains
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Relative permittivity and permeability of a material are
ϵ
r
and
μ
r
, respectively. Which of the following values of these quantifies are allowed for a diamagnetic material?
A
ϵ
r
=
0
.
5
,
μ
r
=
0
.
5
B
ϵ
r
=
1
.
5
,
μ
r
=
1
.
5
C
ϵ
r
=
0
.
5
,
μ
r
=
1
.
5
D
ϵ
r
=
1
.
5
,
μ
r
=
0
.
5
Medium
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The B-H curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a ling solenoid with
1
0
0
0
turns/cm.. The current that should be passed in the solenoid to demagnetise the ferromagnet completely is:
A
2
m
A
B
1
m
A
C
3
m
A
D
None of these
Medium
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A tin rectangular magnet suspended freely has a period of oscillation equal to
T
. Now it is broken into equal halves (each having half of the original length) and one piece is mode to oscillate freely in the same field. If its period of oscillation is
T
′
, the ratio
T
T
′
is :
A
3
1
B
2
1
C
2
D
4
1
Medium
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Curie temperature is the temperature above which
A
a ferromagnetic material becomes paramagnetic
B
a paramagnetic material becomes diamagnetic
C
a ferromagnetic material becomes diamagnetic
D
a paramagnetic material becomes ferromagnetic.
Medium
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An example of a perfect diamagnet is a superconductor. This implies that when a superconductor is put in a magnetic field of intensity
B
, the magnetic field
B
S
inside the superconductor will be such that :
A
B
S
=
−
B
B
B
S
=
0
C
B
S
=
B
D
B
S
<
B
but
B
S
=
0
Easy
JEE Mains
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Three identical bars A, B and C are made of different magnetic materials. When kept in a uniform magnetic field, the field lines around them look as given in the figure . Make the correspondence of these bars with their material being diamagnetic (D), ferromagnetic (F) and paramagnetic (P) .
A
A
↔
F
,
B
↔
D
,
C
↔
P
B
A
↔
D
,
B
↔
P
,
C
↔
F
C
A
↔
F
,
B
↔
P
,
C
↔
D
D
A
↔
P
,
B
↔
F
,
C
↔
D
Medium
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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 all three of them.
B
attract
N
1
and
N
2
strongly but repel
N
3
.
C
attract
N
1
strongly,
N
2
weakly and repel
N
3
weakly.
D
attract
N
1
strongly, but repel
N
2
and
N
3
weakly.
Medium
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A planar loops of wire rotates in a uniform magnetic field. Initially, at
t
=
0
, the plane of the loop is perpendicular to the magnetic field. If it rotates with a period of
1
0
s
about an axis in its plane then the magnitude of induced emf will be maximum and minimum, respectively at :
A
5
.
0
s
and
7
.
5
s
B
2
.
5
s
and
7
.
5
s
C
2
.
5
s
and
5
.
0
s
D
5
.
0
s
and
1
0
.
0
s
Hard
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The figure gives experimentally measured B vs. H variation in a ferromagnetic material. The retentivity, co-ercivity and saturation, respectively, of the material are :
A
1
.
5
T
,
5
0
A
/
m
and
1
.
0
T
B
1
5
0
A
/
m
,
1
.
0
T
and
1
.
5
T
C
1
.
5
T
,
5
0
A
/
m
and
1
.
0
T
D
1
.
0
T
,
5
0
A
/
m
and
1
.
5
T
Hard
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