Magnetic Materials

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JEE Advanced 2010

Comprehension Passage

Electrical resistance of certain materials, known as superconductors, changes abruptly from a non-zero value to zero as their temperature is lowered below a critical temperature

T_{C} (0)

. An interesting property of superconductors is that their critical temperature becomes smaller than

T_{C} (0)

if they are placed in a magnetic field i.e. the critical temperature

T_{C} (B)

is a function of the magnetic field strength

B

. The dependence of

T_{C} (B)

B

is shown in the figure.

Question 1:

In the graphs below, the resistance $R$ of a superconductor is shown as a function of its temperature $T$ for two different magnetic fields $B_{1}$ (solid line) and $B_{2}$ (dashed line). If $B_{2}$ is larger than $B_{1}$ , which of the following graphs shows the correct variation of $R$ with $T$ in these fields? (2010)

A superconductor has $T_{C} (0) = 100 K$ . When a magnetic field of 7.5 T is applied, its $T_{C}$ decreases to 75 K. For this material one can definitely say that when (Note T = Tesla) (2010)

(A)

B = 5 T

T_{C} (B) = 80 K

(B)

B = 5 T

75 K < T_{C} (B) < 100 K

(C)

B = 10 T

75 K < T_{C} (B) < 100 K

(D)

B = 10 T

T_{C} (B) = 70 K

JEE Main 2021

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A long solenoid with $1000 turns/m$ has a core material with relative permeability $500$ and volume $1 0^{3} cm^{3}$ . If the core material is replaced by another material having relative permeability of $750$ with same volume maintaining same current of $0.75 A$ in the solenoid, the fractional change in the magnetic moment of the core would be approximately $(\frac{x}{499})$ . Find the value of $x$ .

JEE Main 2020

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A paramagnetic sample shows a net magnetisation of $6 A/m$ , when it is placed in an external magnetic field of $0.4 T$ at a temperature of $4 K$ . When the sample is placed in an external magnetic field of $0.3 T$ at a temperature of $24 K$ , then the magnetisation will be

(A)

4 A/m

উভ 0.75 \text{ A/m}

উভ 1 A/m

উভ 2.25 \text{ A/m}$

JEE Main 2021

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The magnetic susceptibility of a material of a rod is $499$ . Permeability in vacuum is $4 π \times 1 0^{- 7} H/m$ . Absolute permeability of the material of the rod is

(A)

4 π \times 1 0^{- 4} H/m

(B)

2 π \times 1 0^{- 4} H/m

(C)

3 π \times 1 0^{- 4} H/m

(D)

π \times 1 0^{- 4} H/m

JEE Main 2020

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A perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a paramagnetic substance. The whole system is placed in a uniform magnetic field $B$ . Then, the field inside the paramagnetic substance is

(A)

much larger than

∣ B ∣

and parallel to

B

(B)

B

∣ B ∣

but opposite to

B

JEE Main 2020

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An iron rod of volume $1 0^{- 3} m^{3}$ and relative permeability $1000$ is placed as core in a solenoid with $10 turns/cm$ . If a current of $0.5 A$ is passed through the solenoid, then the magnetic moment of the rod will be

(A)

50 \times 1 0^{2} Am^{2}

(B)

5 \times 1 0^{2} Am^{2}

(C)

500 \times 1 0^{2} Am^{2}

(D)

0.5 \times 1 0^{2} Am^{2}

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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 quantities are allowed for a diamagnetic material?

(A)

ε_{r} = 0.5, μ_{r} = 1.5

(B)

ε_{r} = 1.5, μ_{r} = 0.5

(C)

ε_{r} = 0.5, μ_{r} = 0.5

(D)

ε_{r} = 1.5, μ_{r} = 1.5

JEE Main 2014

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The coercivity of a small magnet where the ferromagnet gets demagnetised is $3 \times 1 0^{3} Am^{- 1}$ . The current required to be passed in a solenoid of length $10 cm$ and number of turns $100$ , so that the magnet gets demagnetised when inside the solenoid is

The figure gives experimentally measured $B$ versus $H$ variation in a ferromagnetic material. The retentivity, coercivity and saturation respectively of the material are

(A)

1.0 T, 50 A/m and 1.5 T

(B)

150 A/m, 1.0 T and 1.5 T

(C)

1.5 T, 50 A/m and 1.0 T

(D)

1.5 T, 50 A/m and 1.0 T

JEE Main 2016

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Hysteresis loops for two magnetic materials A and B are as given below These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then, it is proper to use

(A)

A for electric generators and transformers

(B)

A for electromagnets and B for electric generators

(C)

A for transformers and B for electric generators

(D)

B for electromagnets and transformers

JEE Main 2021

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Statement I: The ferromagnetic property depends on temperature. At high temperature, ferromagnet becomes paramagnet. Statement II: At high temperature, the domain wall area of a ferromagnetic substance increases. In the light of the above statements, choose the most appropriate answer from the options given below.

(A)

Statement I is true but Statement II is false

(B)

Both Statement I and Statement II are true

(C)

Both Statement I and Statement II are false

(D)

Statement I is false but Statement II is true

LEVELBoard

Curie temperature is the temperature above which

(A)

a ferromagnetic material becomes para-magnetic

(B)

a paramagnetic material becomes dia-magnetic

(C)

a ferromagnetic material becomes dia-magnetic

(D)

a paramagnetic material becomes ferro-magnetic

JEE Main 2021

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Which of the following statements are correct? A. Electric monopoles do not exist, whereas magnetic monopoles exist. B. Magnetic field lines due to a solenoid at its ends and outside cannot be completely straight and confined. C. Magnetic field lines are completely confined within a toroid. D. Magnetic field lines inside a bar magnet are not parallel. E. $χ = - 1$ is the condition for a perfect diamagnetic material, where $χ$ is its magnetic susceptibility. Choose the correct answer from the options given below.

A paramagnetic material has $1 0^{28} atoms/m^{3}$ . Its magnetic susceptibility at temperature $350 K$ is $2.8 \times 1 0^{- 4}$ . Its susceptibility at $300 K$ is

(A)

3.726 \times 1 0^{- 4}

(B)

3.672 \times 1 0^{- 4}

(C)

2.672 \times 1 0^{- 4}

(D)

3.267 \times 1 0^{- 4}

JEE Main 2021

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In a ferromagnetic material, below the Curie temperature, a domain is defined as

(A)

a macroscopic region with zero magnetisation

(B)

a macroscopic region with saturation magnetisation

(C)

a macroscopic region with randomly oriented magnetic dipoles

(D)

a macroscopic region with consecutive magnetic dipoles oriented in opposite direction

LEVELJEE Main

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

JEE Main 2020

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Magnetic materials used for making permanent magnets (P) and magnets in a transformer (T) have different properties, of the following, which property best matches for the type of magnet required?

(A)

T: Large retentivity, small coercivity

(B)

P : Large retentivity, large coercivity

(C)

P : Small retentivity, large coercivity

(D)

T : Large retentivity, large coercivity

JEE Main 2019

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A bar magnet is demagnetised by inserting it inside a solenoid of length $0.2 m$ , $100$ turns and carrying a current of $5.2 A$ . The coercivity of the bar magnet is

(A)

1200 A/m

(B)

285 A/m

(C)

2600 A/m

(D)

520 A/m

JEE Main 2019

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A paramagnetic substance in the form of a cube with sides $1 cm$ has a magnetic dipole moment of $20 \times 1 0^{- 6} J/T$ when a magnetic intensity of $60 \times 1 0^{3} A/m$ is applied. Its magnetic susceptibility is

(A)

3.3 \times 1 0^{- 4}

(B)

3.3 \times 1 0^{- 2}

(C)

4.3 \times 1 0^{- 2}

(D)

2.3 \times 1 0^{- 2}

LEVELBoard

The materials suitable for making electro- magnets should have

(A)

high retentivity and high coercivity

(B)

low retentivity and low coercivity

(C)

high retentivity and low coercivity

(D)

low retentivity and high coercivity

Comprehension Passage

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } The magnetic susceptibility of a material of a rod is 499. Permeability in vacuum is 4π×10−7 H/m. Absolute permeability of the material of the rod is

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } The figure gives experimentally measured B versus H variation in a ferromagnetic material. The retentivity, coercivity and saturation respectively of the material are

Hysteresis loops for two magnetic materials A and B are as given below These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then, it is proper to use

Curie temperature is the temperature above which

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } A paramagnetic material has 1028 atoms/m3. Its magnetic susceptibility at temperature 350 K is 2.8×10−4. Its susceptibility at 300 K is

In a ferromagnetic material, below the Curie temperature, a domain is defined as

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } Needles N1​,N2​ and N3​ are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will

Magnetic materials used for making permanent magnets (P) and magnets in a transformer (T) have different properties, of the following, which property best matches for the type of magnet required?

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } A bar magnet is demagnetised by inserting it inside a solenoid of length 0.2 m, 100 turns and carrying a current of 5.2 A. The coercivity of the bar magnet is

The materials suitable for making electro- magnets should have

The magnetic susceptibility of a material of a rod is $499$ . Permeability in vacuum is $4 π \times 1 0^{- 7} H/m$ . Absolute permeability of the material of the rod is

The figure gives experimentally measured $B$ versus $H$ variation in a ferromagnetic material. The retentivity, coercivity and saturation respectively of the material are

A paramagnetic material has $1 0^{28} atoms/m^{3}$ . Its magnetic susceptibility at temperature $350 K$ is $2.8 \times 1 0^{- 4}$ . Its susceptibility at $300 K$ is

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 bar magnet is demagnetised by inserting it inside a solenoid of length $0.2 m$ , $100$ turns and carrying a current of $5.2 A$ . The coercivity of the bar magnet is