Quiz Tweek

Preparing your workspace...

Magnetism and Matter Set-3 MCQ Online Practice Test | Class 12 | Quiz Tweek

Magnetism and Matter Set-3

Practice Important MCQs for Magnetism and Matter — Physics, Class 12.

Magnetism and Matter connects microscopic magnetic moments and macroscopic fields through concepts such as magnetization, susceptibility, permeability, demagnetizing factors and hysteresis. Mastery of these topics is crucial for board exams and competitive tests because many problems require combining formulas with shape-dependent reasoning, energy considerations and interpreting M–H/B–H curves rather than mere recall.

This set focuses on multi-step reasoning: calculating fields and forces in the presence of magnetic materials, analysing hysteresis and temperature effects, and resolving common misconceptions (shape vs material dependence, sphere vs cylinder, open vs closed circuits). Practising these problems strengthens both numerical skills and conceptual understanding needed for CBSE, JEE and NEET level questions.

Minutes

Questions

1 / -0

Marking

Question Bank Preview

Q1. A long solenoid (length ≫ radius) has $n=800\ \text{turns m}^{-1}$ and carries current $I=0.50\ \mathrm{A}$ . The core is filled with a linear magnetic material of volume susceptibility $\chi=2.5$ . Assuming the demagnetizing factor is negligible, calculate the magnetic induction $B$ inside the core. (Use $\mu_0=4\pi\times10^{-7}\ \mathrm{N/A^2}$ and $B=\mu_0(1+\chi)nI$ .)

(A)

$5.03\times10^{-3}\ \mathrm{T}$

(B)

$7.04\times10^{-4}\ \mathrm{T}$

(C)

$1.76\times10^{-3}\ \mathrm{T}$

(D)

$2.80\times10^{-3}\ \mathrm{T}$

Q2. A cylindrical specimen with demagnetizing factor $N=0.10$ (axis along applied field) is placed in an external uniform field $H_0=1000\ \mathrm{A/m}$ . The material is linear with susceptibility $\chi=50$ . Using $H_{\rm int}=\dfrac{H_0}{1+N\chi}$ and $B=\mu_0(1+\chi)H_{\rm int}$ , find the magnetic induction $B$ inside the specimen. (Take $\mu_0=4\pi\times10^{-7}\ \mathrm{N/A^2}$ .)

(A)

$5.34\times10^{-3}\ \mathrm{T}$

(B)

$1.07\times10^{-2}\ \mathrm{T}$

(C)

$2.14\times10^{-2}\ \mathrm{T}$

(D)

$7.12\times10^{-3}\ \mathrm{T}$

Q3. Two materials X and Y are subjected to the same cyclic magnetising field and yield the following qualitative hysteresis loops: Loop X is very narrow with a small coercive field and small area; Loop Y is wide with large coercivity and large loop area. Which option best follows from these observations?

(A)

Material X is suitable for permanent magnets and Y is ideal for transformer cores.

(B)

Material X has larger remanent magnetisation than Y.

(C)

Loop area depends only on saturation magnetisation, so Y must have a higher saturation than X.

(D)

Material X is a soft magnetic material (low coercivity, low hysteresis loss) suitable for transformer cores, while Y is a hard magnetic material (high coercivity, high hysteresis loss) suitable for permanent magnets.

Q4. Assertion: For a very long slender ferromagnetic rod magnetised along its axis, the demagnetising field inside is negligible compared to the applied field, so the internal magnetising field is approximately the applied field.
Reason: The demagnetising factor $N$ for an axially magnetised long rod tends to zero because the surface pole distribution produces little opposing internal field.

(A)

Both Assertion and Reason are true and Reason is the correct explanation of the Assertion.

(B)

Both Assertion and Reason are true but Reason is NOT the correct explanation of the Assertion.

(C)

Assertion is true but Reason is false.

(D)

Assertion is false but Reason is true.

Q5. A small spherical paramagnetic particle (volume susceptibility $\chi=2.0\times10^{-2}$ ) is placed in vacuum in a uniform external magnetic induction $B_0=0.100\ \mathrm{T}$ . For a sphere the demagnetising factor is $N=1/3$ . Assuming linear response, compute the magnetisation $M$ inside the sphere. (Use $\mu_0=4\pi\times10^{-7}\ \mathrm{N/A^2}$ and $H_0=B_0/\mu_0$ .)

(A)

$1.58\times10^{3}\ \mathrm{A/m}$

(B)

$1.58\times10^{2}\ \mathrm{A/m}$

(C)

$7.90\times10^{4}\ \mathrm{A/m}$

(D)

$3.16\times10^{3}\ \mathrm{A/m}$

Q6. A linear, non-hysteretic magnetic material has relative permeability $\mu_r=100$ and is subjected to an applied field $H=800\ \mathrm{A/m}$ . Using the relation for magnetic energy density in a linear medium $u=\tfrac{1}{2}\,B\cdot H=\tfrac{1}{2}\mu_0\mu_r H^2$ , calculate the magnetic energy stored per unit volume.

(A)

$8.04\times10^{1}\ \mathrm{J/m^3}$

(B)

$4.02\times10^{1}\ \mathrm{J/m^3}$

(C)

$4.02\ \mathrm{J/m^3}$

(D)

$4.02\times10^{2}\ \mathrm{J/m^3}$

Q7. A long ferromagnetic rod of length $L$ is magnetised along its axis by an external field $H_0$ , producing magnetisation $M_0$ . The rod is then cut into two identical rods of length $L/2$ and the halves are separated so each is isolated in the same external field $H_0$ . Neglecting interactions between pieces beyond the shape-dependent demagnetising factor, which statement best describes the magnetisation $M$ of each half compared to $M_0$ ?

(A)

Each half has magnetisation $M$ smaller than $M_0$ because the demagnetising factor increases for shorter rods, reducing the internal field and hence $M$ .

(B)

Each half has magnetisation equal to $M_0$ because magnetisation is an intrinsic material property independent of shape.

(C)

Each half has magnetisation larger than $M_0$ because cutting reduces domain wall pinning and so increases alignment.

(D)

Each half becomes non-magnetic ( $M=0$ ) because cutting creates uncompensated magnetic charges that cancel magnetisation.

Q8. For a ferromagnetic sample measured at two temperatures T1 and T2, the following qualitative M–H behaviours are observed: Curve P shows a hysteresis loop with remanence and coercivity; Curve Q is a straight line through the origin with a small positive slope. Which assignment is correct regarding the Curie temperature $T_C$ ?

(A)

Curve P corresponds to $T>T_C$ and Curve Q to $T<T_C$ .

(B)

Both curves correspond to $T<T_C$ but with different pinning strengths.

(C)

Both curves correspond to $T>T_C$ ; one just has larger susceptibility.

(D)

Curve P is measured at $T<T_C$ (ferromagnetic — hysteresis), while Curve Q is at $T>T_C$ (paramagnetic — linear response).

Q9. A small paramagnetic bead of volume $V=1.0\times10^{-6}\ \mathrm{m^3}$ and susceptibility $\chi=1.0\times10^{-2}$ is placed near $x=0$ in a magnetic field $H(x)=H_0(1+\alpha x)$ with $H_0=1.0\times10^{4}\ \mathrm{A/m}$ and $\alpha=0.10\ \mathrm{m^{-1}}$ . For a small linear sample, the magnetic force may be approximated as $\vec{F}=\dfrac{1}{2}\mu_0\chi V\nabla(H^2)$ . Calculate the magnitude of the force at $x=0$ (use $\mu_0=4\pi\times10^{-7}\ \mathrm{N/A^2}$ ).

(A)

$6.28\times10^{-8}\ \mathrm{N}$

(B)

$1.26\times10^{-7}\ \mathrm{N}$

(C)

$2.51\times10^{-6}\ \mathrm{N}$

(D)

$1.26\times10^{-5}\ \mathrm{N}$

Q10. Assertion: In a linear isotropic magnetic material the vectors $\vec{B}$ and $\vec{H}$ are always parallel.
Reason: Magnetisation $\vec{M}$ is always perpendicular to the applied field $\vec{H}$ in magnetic materials.

(A)

Both Assertion and Reason are true and Reason is the correct explanation of the Assertion.

(B)

Both Assertion and Reason are true but Reason is NOT the correct explanation of the Assertion.

(C)

Assertion is true but Reason is false.

(D)

Assertion is false but Reason is true.

More Quizzes for Class 12

Explore other chapters and subjects, or view all quizzes for this class.

Quiz Tweek

Magnetism and Matter Set-3

Question Bank Preview

More Quizzes for Class 12

Chemistry

Mathematics

Physics