JEE Main Magnetism and Matter PYQ

6. (JEE Main 2021 (Online) 22th July Evening Shift)

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 false but Statement II is true

B. Statement I is true but Statement II is false

C. Both Statement I and Statement II are false

D. Both Statement I and Statement II are true

Correct Option is (B)

With increase in temperature domain volume decreases. Statement I true Statement 2 false

7. (JEE Main 2021 (Online) 18th March Evening Shift)

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 x is its magnetic susceptibility.

Choose the correct answer from the options given below :

A. (A) and (B) only

B. (B) and (C) only

C. (C) and (E) onlyp>

D. (B) and (D) only

Correct Option is (C)

(a) Electric monopoles exist while magnetic monopoles do not exist.

(b) Magnetic field lines at the ends and outside of solenoid cannot be confined. (c) Magnetic field lines are confined within a toroid.

(d) Magnetic field lines inside a bar magnet are parallel.

(e) For perfectly diamagnetic material $χ$ = -1.

8. (JEE Main 2021 (Online) 25th February Evening Shift)

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

A. a macroscopic region with zero magnetization.

B. a macroscopic region with saturation magnetization.

C. a macroscopic region with randomly oriented magnetic dipoles.

D. a macroscopic region with consecutive magnetic dipoles oriented in opposite direction.

Correct Option is (B)

In a ferromagnetic material, below the curie temperature a domain is defined as a macroscopic region with saturation magnetization.

9. (JEE Main 2021 (Online) 24th February Evening Shift)

A soft ferromagnetic material is placed in an external magnetic field. The magnetic domains :

A. may increase or decrease in size and change its orientation.

B. increase in size but no change in orientation.

C. decrease in size and changes orientation.

D. have no relation with external magnetic field.

Correct Option is (A)

Atoms of ferromagnetic material in unmagnetised state form domains inside the ferromagnetic material. These domains have large magnetic moment of atoms. In the absence of magnetic field, these domains have magnetic moment in different directions. But when the magnetic field is applied, domains aligned in the direction of the field grow in size and those aligned in the direction opposite to the field reduce in size and also its orientation changes.

10. (JEE Main 2020 (Online) 4th September Evening Slot)

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

B. 1 A/m

C. 0.75 A/m

D. 2.25 A/m

Correct Option is (C)

According to curies law

$χ$ $= \frac{C B_{e x t}}{T}$

$\Rightarrow$ $6 = \frac{C \times 0.4}{4}$

$\Rightarrow C = 60$

$∴$ Case - II : $χ$ $= \frac{60 \times 0.3}{24}$ $= \frac{60 \times 3}{240} = \frac{3}{4} = 0.75 A / m$