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Physics
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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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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
JEE Mains
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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
JEE Mains
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>