The unit of $ \frac{\mu_{0}}{4 \pi} $ is

$ \mathrm{Nm}^{2} \mathrm{C}^{2} $

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JEE • PHYSICS • MAGNETISM AND MATTER

Magnetism and matter practice · Medium

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Practice format and chapter quiz

These sets use single-correct-answer MCQs. They do not cover every JEE Main or JEE Advanced question format and are not full-length mock papers.

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Showing 301-323 of 323 questions

301 Medium

301 of 323

Understanding +4 | -1

Which of the following properties is 'False' for
a bar magnet ?

View answer and explanation

Correct option: A

It doesn't produce magnetic field

Option A (It doesn't produce magnetic field) is correct because a bar magnet inherently produces a magnetic field.

302 Medium

302 of 323

Understanding +4 | -1

The oscillating electric and magnetic field vectors of electromagnetic wave are oriented along

View answer and explanation

Correct option: C

mutually perpendicular directions and are in same phase

Option C (mutually perpendicular directions and are in same phase) is correct because the electric and magnetic fields in an electromagnetic wave are perpendicular to each other and oscillate in phase.

303 Medium

303 of 323

Understanding +4 | -1

If there is no torsion in the suspension thread, then the time period of a magnet executing

\mathrm{SHM}

is :

View answer and explanation

Correct option: A

\mathrm{T}=2 \pi \sqrt{\frac{\mathrm{I}}{\mathrm{MB}}}

Option A (

\mathrm{T}=2 \pi \sqrt{\frac{\mathrm{I}}{\mathrm{MB}}}

) is correct because it represents the standard formula for the time period of a magnet in SHM without torsion.

304 Medium

304 of 323

Remembering +4 | -1

Meissner effect is related to

View answer and explanation

Correct option: B

Superconductors

Option B (Superconductors) is correct because the Meissner effect is a characteristic property of superconductors.

305 Medium

305 of 323

Understanding +4 | -1

The relation between total magnetic field (B), magnetic intensity

(\mathrm{H})

, permeability of free space

\left(\mu_0\right)

and susceptibility

(\chi)

View answer and explanation

Correct option: B

\frac{\mathrm{B}}{\mathrm{H}}=\mu_0(1+\chi)

Option B (

\frac{\mathrm{B}}{\mathrm{H}}=\mu_0(1+\chi)

) is correct because it represents the relationship between magnetic field, magnetic intensity, permeability, and susceptibility.

306 Medium

306 of 323

Understanding +4 | -1

Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show

View answer and explanation

Correct option: A

Paramagnetism

Option A (Paramagnetism) is correct because above the Curie temperature, ferromagnetic materials lose their long-range order and become paramagnetic, where atomic magnetic moments align weakly with an external field.

307 Medium

307 of 323

Application +4 | -1

3 {~cm} \times 10 {~cm}

rectangular coil with number of turns 300 is placed in uniform magnetic field of strength

0.2 {~T}

. The maximum magnetic torque acting on it when a current of

10^{-4} {~A}

is passed through it; 

View answer and explanation

Correct option: D

1.8 \times 10^{-5} {Nm}

Option D (

1.8 \times 10^{-5} {Nm}

) is correct because it is the maximum torque calculated using the formula

\tau = NIBA \sin \theta

with

\theta = 90^{\circ}

308 Medium

308 of 323

Understanding +4 | -1

Due to the earth’s magnetic field, charged cosmic ray particles

View answer and explanation

Correct option: C

Can never reach the equator

Option A (Require greater kinetic energy to reach the equator than the poles) is correct because charged particles are deflected more strongly near the equator due to the Earth's magnetic field, requiring more energy to overcome this deflection.

309 Medium

309 of 323

Understanding +4 | -1

A bar magnet is characterized by

View answer and explanation

Correct option: D

all of these

Option D (all of these) is correct because a bar magnet exhibits directional properties, attracts magnetic materials, and induces magnetism in other materials.

310 Medium

310 of 323

Application +4 | -1

A magnet placed in the magnetic meridian with its north pole pointing north of the earth produces a neutral point at a distance of

0.15 \mathrm{~m}

from either pole. It is then broken into two equal pieces and one such piece is placed in a similar position. Find the position of the neutral point.

View answer and explanation

Correct option: A

0.119 m

Option A (0.119 m) is correct because when the magnet is broken, its magnetic moment changes, and the new distance to the neutral point can be calculated using the relationship between magnetic field and distance.

311 Medium

311 of 323

Understanding +4 | -1

Assertion (A): Electromagnets are made of soft iron.

Reason (R): Coercivity of soft iron is small.

View answer and explanation

Correct option: A

If both (A) and (R) are true and the (R) is a correct explanation of the (A)

Option A (If both (A) and (R) are true and the (R) is a correct explanation of the (A)) is correct because electromagnets need to be easily magnetized and demagnetized, which is facilitated by the low coercivity of soft iron.

312 Medium

312 of 323

Understanding +4 | -1

If the susceptibility of dia, para and ferro magnetic materials are

\chi_{\mathrm{d}}, \chi_{\mathrm{p}}, \chi_{\mathrm{f}}

respectively, then

View answer and explanation

Correct option: A

\chi_{\mathrm{d}} < \chi_{\mathrm{p}} < \chi_{\mathrm{f}}

Option C (The velocity at the highest point is directed along the horizontal) is correct because at the highest point, the vertical component of velocity is zero, leaving only the horizontal component.

313 Medium

313 of 323

Application +4 | -1

In the magnetic meridian of a certain place, the horizontal component of the Earth's magnetic field is

86.6 \mathrm{~G}

(Gauss) and the magnetic field of earth is

100 \mathrm{~G}

(Gauss). Then the dip angle is

View answer and explanation

Correct option: C

30^{\circ}

Option C (

30^{\circ}

) is correct because the dip angle is calculated using the horizontal component and the Earth's magnetic field.

314 Medium

314 of 323

Understanding +4 | -1

\chi_1

and

\chi_2

are susceptibility of a paramagnetic material at temperatures

T_1\,K

and

T_2\,K

respectively, then :

View answer and explanation

Correct option: B

\chi_1 \mathrm{~T}_1=\chi_2 \mathrm{~T}_2

Option C is correct because, according to Curie's law, the magnetic susceptibility of a paramagnetic material is inversely proportional to its temperature.

315 Medium

315 of 323

Understanding +4 | -1

A hydrogen atom is paramagnetic. A hydrogen molecule is

View answer and explanation

Correct option: A

Diamagnetic

Option A (Diamagnetic) is correct because the hydrogen molecule has no unpaired electrons, resulting in a net magnetic moment of zero.

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316 Medium

316 of 323

Understanding +4 | -1

The unit of

\frac{\mu_{0}}{4 \pi}

View answer and explanation

Correct option: B

N A^{-2}

Option B is correct because the unit of

\frac{{\mu_{0}}}{{4 \pi}}

N A^{{-2}}

, derived from the Biot-Savart law or Ampere's law.

317 Medium

317 of 323

Application +4 | -1

A thin magnetic needle oscillates in a horizontal plane with a period

\mathrm{T}

. It is broken into

n

equals parts. The time period of each part will be

View answer and explanation

Correct option: D

\mathrm{T} / \mathrm{n}

Option D (

\mathrm{T} / \mathrm{n}

) is correct because the time period is inversely proportional to the number of parts the needle is broken into.

318 Medium

318 of 323

Remembering +4 | -1

The hysteresis cycle for the material of permanent magnet is

View answer and explanation

Correct option: C

Tall and wide

Option C (Tall and wide) is correct because a permanent magnet needs high coercivity and retentivity, resulting in a tall and wide hysteresis cycle.

319 Medium

319 of 323

Remembering +4 | -1

The value of relative magnetic permeability of
superconductors is:

View answer and explanation

Correct option: A

Option A (0) is correct because superconductors are perfectly diamagnetic, expelling all magnetic fields, resulting in a relative permeability of 0.

320 Medium

320 of 323

Remembering +4 | -1

The earth's magnetic field varies with the ______

View answer and explanation

Correct option: C

both position and time

Option C (both position and time) is correct because the Earth's magnetic field strength and direction vary depending on location and also change over time due to various factors within the Earth.

321 Medium

321 of 323

Understanding +4 | -1

What happens, when a magnetic substance is
heated?

View answer and explanation

Correct option: A

It loses its magnetism

Option A is correct because heating a magnetic substance above its Curie temperature causes it to lose its magnetism due to the randomization of atomic magnetic moments.

322 Medium

322 of 323

Analyzing +4 | -1

Assertion(A): Steel is attracted by a magnet.

Reason (R): Steel is not a magnetic substance.

View answer and explanation

Correct option: C

If (A) is true but the (R) is false

Option C (If (A) is true but the (R) is false) is correct because steel is attracted by a magnet, but steel is a magnetic substance.

323 Medium

323 of 323

Understanding +4 | -1

If the liquid in a U tube rises to a high level in
the limb placed between poles of an
electromagnet, then the liquid is

View answer and explanation

Correct option: C

paramagnetic

Option C is correct because paramagnetic materials are attracted to magnetic fields, causing the liquid to rise between the poles of the electromagnet.

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