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Magnetic Materials — MH-CET Physics MCQs with Solutions
Free MH-CET Physics Magnetic Materials MCQs with step-by-step solutions covering Magnetic Dipole & Bar Magnet, Magnetisation & Magnetic Intensity, Diamagnetism, Paramagnetism & Ferromagnetism, Curie's Law & Curie Temperature, Hysteresis, Earth's Magnetism. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — Magnetic Dipole & Bar Magnet · easy · theory
The magnetic dipole moment of a bar magnet of pole strength $m$ and magnetic length $2l$ is:
A. $2ml^2$
B. $\dfrac{2l}{m}$
C. $m \times 2l$ ✓ Correct
D. $\dfrac{m}{2l}$
Solution: The moment is directed from the south pole to the north pole inside the magnet.
Q2 — Magnetic Dipole & Bar Magnet · easy · theory
The SI unit of magnetic dipole moment is:
A. $\text{A}/\text{m}$
B. $\text{A}\cdot\text{m}$
C. $\text{A}\cdot\text{m}^2$ ✓ Correct
D. $\text{Wb}\cdot\text{m}$
Solution: Equivalently it is joule per tesla, since $U = -MB$.
Q3 — Magnetic Dipole & Bar Magnet · easy · theory
Isolated magnetic poles (monopoles) do not exist. The experimental evidence is that:
A. A freely suspended magnet points north
B. Like poles repel each other
C. Breaking a magnet always produces two complete magnets, each with both poles ✓ Correct
D. A magnet loses its magnetism when heated
Solution: However finely a magnet is divided, each fragment is a complete dipole — magnetic field lines are always closed loops.
Q4 — Magnetic Dipole & Bar Magnet · easy · theory
The torque on a bar magnet of moment $M$ placed at angle $\theta$ in a uniform field $B$ is:
A. $\dfrac{MB}{\sin\theta}$
B. $MB\cos\theta$
C. $MB\tan\theta$
D. $MB\sin\theta$ ✓ Correct
Solution: It is greatest when the magnet lies across the field and vanishes when it is aligned with it.
Q5 — Magnetic Dipole & Bar Magnet · easy · numerical
A magnet of moment $0.5\text{ A}\cdot\text{m}^2$ is placed in a field of $0.2\text{ T}$. The maximum torque on it is:
A. $0.1\text{ N}\cdot\text{m}$ ✓ Correct
B. $2.5\text{ N}\cdot\text{m}$
C. $0.25\text{ N}\cdot\text{m}$
D. $0.7\text{ N}\cdot\text{m}$
Solution: $\tau_{max} = MB = 0.5 \times 0.2 = 0.1\text{ N}\cdot\text{m}$.
Q6 — Magnetic Dipole & Bar Magnet · easy · numerical
A bar magnet of magnetic length $0.1\text{ m}$ has pole strength $20\text{ A}\cdot\text{m}$. Its magnetic moment is:
A. $2\text{ A}\cdot\text{m}^2$ ✓ Correct
B. $0.2\text{ A}\cdot\text{m}^2$
C. $20\text{ A}\cdot\text{m}^2$
D. $200\text{ A}\cdot\text{m}^2$
Solution: $M = m \times 2l = 20 \times 0.1 = 2\text{ A}\cdot\text{m}^2$.
Q7 — Magnetisation & Magnetic Intensity · easy · theory
The intensity of magnetisation of a material is defined as:
A. The pole strength per unit area
B. The magnetic moment per unit volume ✓ Correct
C. The flux per unit area
D. The magnetic moment per unit mass
Solution: Its SI unit is $\text{A}/\text{m}$, the same as that of magnetic intensity $H$.
Q8 — Magnetisation & Magnetic Intensity · easy · theory
The SI unit of magnetic intensity $H$ is:
A. $\text{A}\cdot\text{m}$
B. $\text{A}/\text{m}$ ✓ Correct
C. $\text{Wb}$
D. $\text{T}$
Solution: $H$ describes the magnetising field produced by free currents, independent of the material's response.
Q9 — Magnetisation & Magnetic Intensity · easy · theory
The magnetic permeability of a material is defined as:
A. $\mu = \dfrac{H}{B}$
B. $\mu = \dfrac{B}{H}$ ✓ Correct
C. $\mu = BH$
D. $\mu = \dfrac{M}{H}$
Solution: It measures how much magnetic induction a given magnetising field produces in the material.
Q10 — Magnetisation & Magnetic Intensity · easy · theory
For a diamagnetic material, the magnetic susceptibility is:
A. Large and positive
B. Small and positive
C. Small and negative ✓ Correct
D. Exactly zero
Solution: The induced magnetisation opposes the applied field, so $M$ and $H$ have opposite signs.
Q11 — Magnetisation & Magnetic Intensity · easy · theory
Magnetic flux through a surface of area $A$ placed perpendicular to a field $B$ is:
A. $BA$, measured in weber ✓ Correct
B. $BA$, measured in tesla
C. $\dfrac{A}{B}$, measured in weber
D. $\dfrac{B}{A}$, measured in tesla
Solution: One weber is one tesla square metre; flux is a scalar quantity.
Q12 — Magnetisation & Magnetic Intensity · easy · numerical
A material has magnetic susceptibility $999$. Its relative permeability is:
A. $998$
B. $999$
C. $1$
D. $1000$ ✓ Correct
Solution: $\mu_r = 1 + \chi = 1 + 999 = 1000$.
Q13 — Magnetisation & Magnetic Intensity · easy · numerical
A material has relative permeability $5000$. Its magnetic susceptibility is:
A. $5001$
B. $0.0002$
C. $4999$ ✓ Correct
D. $5000$
Solution: $\chi = \mu_r - 1 = 5000 - 1 = 4999$.
Q14 — Magnetisation & Magnetic Intensity · easy · numerical
A field of $0.2\text{ T}$ passes normally through an area of $0.05\text{ m}^2$. The magnetic flux is:
A. $0.25\text{ Wb}$
B. $0.1\text{ Wb}$
C. $0.01\text{ Wb}$ ✓ Correct
D. $4\text{ Wb}$
Solution: $\Phi = BA = 0.2 \times 0.05 = 0.01\text{ Wb}$.
Q15 — Diamagnetism, Paramagnetism & Ferromagnetism · easy · theory
The magnetic susceptibility of a paramagnetic substance is:
A. Large and positive
B. Large and negative
C. Small and negative
D. Small and positive ✓ Correct
Solution: Permanent atomic dipoles align partially with the applied field, giving a weak positive magnetisation.
Q16 — Diamagnetism, Paramagnetism & Ferromagnetism · easy · theory
The magnetic susceptibility of a ferromagnetic substance is:
A. Very large and positive ✓ Correct
B. Small and positive
C. Zero
D. Very large and negative
Solution: Domain alignment produces magnetisation thousands of times greater than the applied magnetising field.
Q17 — Diamagnetism, Paramagnetism & Ferromagnetism · easy · theory
A paramagnetic substance placed in a non-uniform magnetic field is:
A. Strongly attracted and retains magnetism
B. Strongly repelled
C. Feebly attracted towards the stronger part of the field ✓ Correct
D. Unaffected
Solution: Its dipoles align with the field, giving a weak attraction that disappears when the field is removed.
Q18 — Diamagnetism, Paramagnetism & Ferromagnetism · easy · theory
Bismuth, copper and water are examples of:
A. Superconductors
B. Diamagnetic substances ✓ Correct
C. Ferromagnetic substances
D. Paramagnetic substances
Solution: These have no net atomic magnetic moment, so only the induced opposing effect appears.
Q19 — Diamagnetism, Paramagnetism & Ferromagnetism · easy · numerical
A material has a magnetic susceptibility of $-10^{-5}$. It is:
A. Non-magnetic
B. Paramagnetic
C. Diamagnetic ✓ Correct
D. Ferromagnetic
Solution: A small negative susceptibility is the signature of diamagnetism.
Q20 — Diamagnetism, Paramagnetism & Ferromagnetism · easy · numerical
A material has a magnetic susceptibility of $+10^{-3}$. It is:
A. Paramagnetic ✓ Correct
B. Diamagnetic
C. Superconducting
D. Ferromagnetic
Solution: A small positive susceptibility indicates paramagnetism.
Q21 — Diamagnetism, Paramagnetism & Ferromagnetism · easy · numerical
A material has a magnetic susceptibility of $1000$. It is:
A. Non-magnetic
B. Diamagnetic
C. Paramagnetic
D. Ferromagnetic ✓ Correct
Solution: Only ferromagnetic materials show susceptibilities of this order.
Q22 — Diamagnetism, Paramagnetism & Ferromagnetism · easy · numerical
A material has relative permeability of the order of $10^3$. It is:
A. Paramagnetic
B. Ferromagnetic ✓ Correct
C. Diamagnetic
D. A vacuum
Solution: Such a large $\mu_r$ is characteristic of ferromagnetic materials like soft iron.
Q23 — Curie's Law & Curie Temperature · easy · theory
Curie's law for a paramagnetic material states that the susceptibility is:
A. Independent of temperature
B. Proportional to the square of the temperature
C. Inversely proportional to the absolute temperature ✓ Correct
D. Directly proportional to the absolute temperature
Solution: $\chi = \dfrac{C}{T}$, where $C$ is the Curie constant of the material.
Q24 — Curie's Law & Curie Temperature · easy · theory
The Curie temperature of a ferromagnetic material is the temperature above which it:
A. Becomes superconducting
B. Loses all magnetic response
C. Becomes paramagnetic ✓ Correct
D. Becomes diamagnetic
Solution: Thermal agitation destroys the spontaneous domain alignment, leaving only weak paramagnetic behaviour.
Q25 — Curie's Law & Curie Temperature · easy · theory
In the relation $\chi = \dfrac{C}{T}$, the constant $C$ is called the:
A. Curie constant ✓ Correct
B. Weiss constant
C. Boltzmann constant
D. Permeability constant
Solution: It depends on the material, being proportional to the number density and the square of the atomic magnetic moment.
Q26 — Curie's Law & Curie Temperature · easy · numerical
The absolute temperature of a paramagnetic sample is doubled. Its susceptibility becomes:
A. Half as large ✓ Correct
B. Four times as large
C. Unchanged
D. Twice as large
Solution: By Curie's law $\chi \propto \dfrac{1}{T}$.
Q27 — Hysteresis · easy · theory
Magnetic hysteresis is the phenomenon in which:
A. The material loses all magnetism instantly
B. The magnetising field lags behind the induction
C. The magnetic induction lags behind the magnetising field ✓ Correct
D. The susceptibility becomes negative
Solution: Because domain walls do not move reversibly, $B$ depends on the previous magnetic history of the specimen.
Q28 — Hysteresis · easy · theory
The material chosen for a transformer core must have a hysteresis loop of:
A. Large area
B. Small area ✓ Correct
C. Zero retentivity and zero permeability
D. Rectangular shape with large area
Solution: The core is magnetised and demagnetised many times a second, so the loss per cycle must be as small as possible.
Q29 — Hysteresis · easy · theory
The energy lost during a hysteresis cycle appears as:
A. Heat in the material ✓ Correct
B. Electrical energy returned to the source
C. Sound
D. Light emitted by the material
Solution: Irreversible domain wall motion dissipates the work done by the magnetising field.
Q30 — Hysteresis · easy · numerical
If the area of the hysteresis loop of a core is doubled, the energy lost per cycle:
A. Becomes four times
B. Halves
C. Remains unchanged
D. Doubles ✓ Correct
Solution: Energy loss per unit volume per cycle is exactly the loop area.