Magnetism and Matter | Physics JEE Main questions with Solutions

Q 1 :

Paramagnetic substances

A. align themselves along the directions of external magnetic field.

B. attract strongly towards external magnetic field.

C. has susceptibility little more than zero.

D. move from a region of strong magnetic field to weak magnetic field.

Choose the most appropriate answer from the options given below: [2024]

A, C only
B, D only
A, B, C, D
A, B, C only

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(1)

(A) align themselves along the directions of external magnetic field.

(C) has susceptibility little more than zero.

A, C only

Q 2 :

The coercivity of a magnet is $5 \times 10^{3}$ A/m. The amount of current required to be passed in a solenoid of length 30 cm and the number of turns 150, so that the magnet gets demagnetised when inside the solenoid is _____ A. [2024]

0%

(10) $L e n g t h o f s o l e n o i d (λ) = 30 c m, N o . o f t u r n s (n) = 150$ $a n d$ $H = 5 \times 10^{3}$ $A / m$

$W e k n o w n = \frac{N}{I} \Rightarrow I = \frac{N}{n}$

$I = \frac{5 \times 10^{3} \times 0.3}{150} = 10 A$

Q 3 :

Match List-I with List-II [2024]

Choose the correct answer from the options given below:

(A)-(III), (B)-(I), (C)-(IV), (D)-(II)
(A)-(III), (B)-(IV), (C)-(I), (D)-(II)
(A)-(I), (B)-(III), (C)-(II), (D)-(IV)
(A)-(IV), (B)-(I), (C)-(III), (D)-(II)

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(1)

Q 4 :

The relationship between the magnetic susceptibility ( $χ$ ) and the magnetic permeability ( $μ$ ) is given by:

( $μ_{0}$ is the permeability of free space and $μ_{r}$ is relative permeability) [2025]

$χ = \frac{μ}{μ_{0}} - 1$
$χ = \frac{μ_{r}}{μ_{0}} + 1$
$χ = μ_{T} + 1$
$χ = 1 - \frac{μ}{μ_{0}}$

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We have

$μ_{r} = (1 + χ) \Rightarrow χ = (μ_{r} - 1)$

$μ = μ_{0} μ_{r} \Rightarrow μ_{r} = \frac{μ}{μ_{0}}$

$∴ χ = (\frac{μ}{μ_{0}} - 1)$

Q 5 :

The percentage increase in magnetic field (B) when space within a current carrying solenoid is filled with magnesium (magnetic susceptibility $χ_{mg} = 1.2 \times 10^{- 5}$ ) is [2025]

$\frac{6}{5} \times 10^{- 3} %$
$\frac{5}{6} \times 10^{- 5} %$
$\frac{5}{6} \times 10^{- 4} %$
$\frac{5}{3} \times 10^{- 5} %$

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(1)

% change in $B = \frac{△ B}{B} % = \frac{B_{new} - B_{old}}{B_{old}} \times 100 %$

$= \frac{μ n i - μ_{0} n i}{μ_{0} n i} \times 100 % = \frac{(μ - μ_{0})}{μ_{0}} \times 100 %$

$= \frac{(μ_{0} μ_{r} - μ_{0})}{μ_{0}} \times 100 %$

$= (μ_{r} - 1) \times 100 %$

$= χ_{n} \times 100 % = 1.2 \times 10^{- 3} %$

Q 6 :

Certain galvanometers have a fixed core made of non-magnetic metallic material. The function of this metallic material is [2023]

to make the magnetic field radial
to bring the coil to rest quickly
to produce large deflecting torque on the coil
to oscillate the coil in magnetic field for longer period of time

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(2)

Due to motion of the coil eddy current develops thus bringing the coil to rest.

Q 7 :

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R [2023]

Assertion A: Electromagnets are made of soft iron.

Reason R: Soft iron has high permeability and low retentivity.

In the light of above statements, choose the most appropriate answer from the options given below.

A is not correct but R is correct
A is correct but R is not correct
Both A and R are correct but R is NOT the correct explanation of A
Both A and R are correct and R is the correct explanation of A

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(4)

Electromagnets are made of soft iron because it has high permeability and low retentivity.

So, Both A and R are correct and R is the correct explanation of A.

Q 8 :

Given below are two statements: [2023]

Statement I For diamagnetic substance $- 1 \leq χ \leq 0$ , where $χ$ is the magnetic susceptibility.

Statement II: Diamagnetic substances when placed in an external magnetic field, tend to move from stronger to weaker part of the field.

In the light of the above statements, choose the correct answer from the options given below.

Both Statement I and Statement II are false.
Both Statement I and Statement II are true.
Statement I is incorrect but Statement II is true.
Statement I is correct but Statement II is false.

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(2)

Both Statements are correct.

Q 9 :

The free space inside a current carrying toroid is filled with a material of susceptibility $2 \times 10^{- 2}$ . The percentage increase in the value of magnetic field inside the toroid will be [2023]

2%
0.2%
0.1%
1%

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(1)

$As χ_{m} = 2 \times 10^{- 2}$

$μ_{r} = 1 + χ_{m} = 1.02 \Rightarrow B = μ_{r} B_{0} = 1.02 B_{0}$

$So percentage increase in magnetic field = 2 %$

Q 10 :

Given below are two statements: [2023]

Statement I: The diamagnetic property depends on temperature.

Statement II: The induced magnetic dipole moment in a diamagnetic sample is always opposite to the magnetizing field.

In the light of given statement, choose the correct answer from the options given below:

Statement I is incorrect but Statement II is true
Both Statement I and Statement II are true
Both Statement I and Statement II are false
Statement I is correct but Statement II is false

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(1)

Conceptual

Topic Question Set

Q 2 :

The coercivity of a magnet is $5 \times 10^{3}$ A/m. The amount of current required to be passed in a solenoid of length 30 cm and the number of turns 150, so that the magnet gets demagnetised when inside the solenoid is _____ A. [2024]

0%

Q 3 :

Match List-I with List-II [2024]

Choose the correct answer from the options given below:

(1)

Q 4 :

The relationship between the magnetic susceptibility ( $χ$ ) and the magnetic permeability ( $μ$ ) is given by:

( $μ_{0}$ is the permeability of free space and $μ_{r}$ is relative permeability) [2025]

Q 5 :

The percentage increase in magnetic field (B) when space within a current carrying solenoid is filled with magnesium (magnetic susceptibility $χ_{mg} = 1.2 \times 10^{- 5}$ ) is [2025]

Q 6 :

Certain galvanometers have a fixed core made of non-magnetic metallic material. The function of this metallic material is [2023]

Q 9 :

The free space inside a current carrying toroid is filled with a material of susceptibility $2 \times 10^{- 2}$ . The percentage increase in the value of magnetic field inside the toroid will be [2023]

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