Q.1 Which property of a magnetic material determines how easily it can be magnetized?
Electrical conductivity
Magnetic susceptibility
Thermal expansion
Specific heat capacity
Explanation - Magnetic susceptibility is a measure of how much a material becomes magnetized in an external magnetic field.
Correct answer is: Magnetic susceptibility
Q.2 In a ferromagnetic material, the alignment of atomic magnetic moments below the Curie temperature is called:
Paramagnetism
Ferromagnetism
Diamagnetism
Antiferromagnetism
Explanation - Ferromagnetism occurs when magnetic moments align spontaneously below the Curie temperature.
Correct answer is: Ferromagnetism
Q.3 Which of the following is a typical soft magnetic material used in transformer cores?
Ferrite
Silicon steel
Nickel
Copper
Explanation - Silicon steel has low coercivity and high permeability, making it ideal for transformer cores.
Correct answer is: Silicon steel
Q.4 The plot of magnetic flux density (B) versus magnetic field strength (H) for a magnetic material is known as:
Hysteresis loop
B-H curve
Curie diagram
Saturation plot
Explanation - The B-H curve, also called a hysteresis loop, shows how B varies with H.
Correct answer is: B-H curve
Q.5 What is the primary reason for the high coercivity of magnetite (Fe3O4) compared to silicon steel?
Higher electrical conductivity
Higher saturation magnetization
Higher crystalline anisotropy
Lower Curie temperature
Explanation - Magnetite’s crystal structure gives it higher anisotropy, leading to higher coercivity.
Correct answer is: Higher crystalline anisotropy
Q.6 In magnetic refrigeration, which effect allows a magnetic material to change its temperature when exposed to a magnetic field?
Peltier effect
Magnetocaloric effect
Seebeck effect
Joule effect
Explanation - The magnetocaloric effect is the change in temperature of a material when its magnetic field changes.
Correct answer is: Magnetocaloric effect
Q.7 Which phenomenon describes the resistance change in a material due to the presence of a magnetic field?
Hall effect
Magnetoresistance
Anomalous Hall effect
Spin Hall effect
Explanation - Magnetoresistance is the change in electrical resistance when a magnetic field is applied.
Correct answer is: Magnetoresistance
Q.8 The maximum energy product (BH)max of a permanent magnet is a figure of merit. Which material typically has the highest (BH)max?
Alnico
Neodymium‑Iron‑Boron (NdFeB)
Samarium‑Cobalt (SmCo)
Ferrite
Explanation - NdFeB magnets have the highest energy product among permanent magnets.
Correct answer is: Neodymium‑Iron‑Boron (NdFeB)
Q.9 Which property of a material determines the extent of magnetic domain wall movement under an external field?
Magnetic anisotropy
Electrical resistivity
Thermal conductivity
Mechanical hardness
Explanation - High anisotropy impedes domain wall motion, affecting magnetization curves.
Correct answer is: Magnetic anisotropy
Q.10 In a hard magnetic material, the ratio of remanent magnetization (Mr) to saturation magnetization (Ms) is:
Close to zero
Close to one
Approximately 0.5
Negative
Explanation - Hard magnets retain most of their saturation magnetization after removal of the field.
Correct answer is: Close to one
Q.11 Which type of magnetic anisotropy originates from shape of the ferromagnetic body?
Magnetocrystalline anisotropy
Shape anisotropy
Stress anisotropy
Exchange anisotropy
Explanation - Shape anisotropy arises due to demagnetizing fields depending on the body’s geometry.
Correct answer is: Shape anisotropy
Q.12 The phenomenon where a material’s magnetization is opposite to the applied field is known as:
Diamagnetism
Paramagnetism
Ferromagnetism
Antiferromagnetism
Explanation - Diamagnetic materials develop a magnetization that opposes the applied field.
Correct answer is: Diamagnetism
Q.13 What does the term 'magnetic permeability' quantify?
Electrical conductivity of a material
Ease of electric current flow
Degree of magnetic flux penetration
Heat transfer capability
Explanation - Permeability measures how easily magnetic flux can permeate a material.
Correct answer is: Degree of magnetic flux penetration
Q.14 Which of these is NOT a typical application of magnetic materials?
Electric motors
Data storage devices
Superconducting magnets
Optical lenses
Explanation - Optical lenses are usually made of glass or plastic; magnetic materials are not used for lenses.
Correct answer is: Optical lenses
Q.15 Which parameter is used to describe the 'softness' of a magnetic material?
Coercivity
Curie temperature
Saturation magnetization
Magnetic anisotropy energy
Explanation - Low coercivity indicates a soft magnetic material, which can be easily magnetized and demagnetized.
Correct answer is: Coercivity
Q.16 In a magnetic hysteresis loop, the area enclosed represents:
Magnetic energy stored
Energy dissipated as heat per cycle
Magnetic field strength
Magnetic flux density
Explanation - The loop area equals the energy loss per magnetic cycle.
Correct answer is: Energy dissipated as heat per cycle
Q.17 The temperature at which a ferromagnetic material becomes paramagnetic is called:
Glass transition temperature
Debye temperature
Curie temperature
Neel temperature
Explanation - Above the Curie temperature, spontaneous magnetization disappears.
Correct answer is: Curie temperature
Q.18 Which magnetic material is commonly used in high‑frequency inductors due to its low core loss?
Ferrite
Soft silicon steel
NdFeB
Alnico
Explanation - Ferrites have low electrical conductivity and thus low eddy‑current losses at high frequencies.
Correct answer is: Ferrite
Q.19 Which property of a magnetic material is directly proportional to the number of unpaired electrons in its atoms?
Curie temperature
Magnetic susceptibility
Saturation magnetization
Coercivity
Explanation - Saturation magnetization depends on the total magnetic moment from unpaired electrons.
Correct answer is: Saturation magnetization
Q.20 The alignment of spins in a ferrimagnetic material results in:
Zero net magnetization
Positive net magnetization
Negative net magnetization
Random net magnetization
Explanation - Ferrimagnets have unequal opposing sublattices, leading to a net magnetization.
Correct answer is: Positive net magnetization
Q.21 What is the main advantage of using nanocrystalline soft magnetic alloys?
High saturation magnetization
Very high coercivity
Low core losses at high frequency
Excellent mechanical hardness
Explanation - Nanocrystalline alloys have small grain size, reducing eddy‑current losses.
Correct answer is: Low core losses at high frequency
Q.22 Which technique is used to measure the magnetic field distribution in a material?
X‑ray diffraction
SQUID magnetometry
SEM imaging
Tensile testing
Explanation - SQUIDs provide highly sensitive magnetic field measurements.
Correct answer is: SQUID magnetometry
Q.23 What role does magnetostriction play in magnetic sensors?
It changes resistance with temperature
It changes shape with magnetic field
It alters optical properties
It modulates electrical capacitance
Explanation - Magnetostriction is the change in dimensions of a material under a magnetic field, used in sensors.
Correct answer is: It changes shape with magnetic field
Q.24 Which material is primarily used for permanent magnets in electric vehicle motors?
Ferrite
NdFeB
Alnico
Iron‑silicon alloy
Explanation - NdFeB provides high magnetic flux density necessary for EV motors.
Correct answer is: NdFeB
Q.25 The anisotropy field (Ha) of a magnet is defined as:
2K1/µ0Ms
K1/µ0Ms
µ0Ms/2K1
µ0Ms/K1
Explanation - The anisotropy field quantifies the field needed to rotate magnetization against anisotropy.
Correct answer is: 2K1/µ0Ms
Q.26 Which of the following best explains why ferrites have high electrical resistivity?
They contain heavy metal ions
They have a non‑metallic crystal structure
They are composed mainly of oxides
They have a high density of free electrons
Explanation - Oxide composition limits free charge carriers, raising resistivity.
Correct answer is: They are composed mainly of oxides
Q.27 What is the consequence of a high Curie temperature in a magnetic material?
It remains magnetic at higher temperatures
It has low saturation magnetization
It shows high coercivity at room temperature
It exhibits strong diamagnetism
Explanation - Curie temperature marks the transition; a higher value means the material stays ferromagnetic longer.
Correct answer is: It remains magnetic at higher temperatures
Q.28 Which property of a magnetic material is affected by the presence of crystalline defects?
Saturation magnetization
Coercivity
Curie temperature
Electrical resistivity
Explanation - Defects pin domain walls, increasing coercivity.
Correct answer is: Coercivity
Q.29 A material that exhibits a hysteresis loop with negligible area is called:
Hard magnetic material
Soft magnetic material
Paramagnetic material
Diamagnetic material
Explanation - Soft magnets have minimal hysteresis loss, indicated by a narrow loop.
Correct answer is: Soft magnetic material
Q.30 The magnetization process in a ferromagnet primarily occurs by:
Creation of electron pairs
Domain wall movement
Spin-flip scattering
Lattice vibrations
Explanation - Domain walls shift to align domains with the external field.
Correct answer is: Domain wall movement
Q.31 Which parameter is defined as the magnetic field needed to reduce the magnetization to zero after saturation?
Remanence
Coercive force
Saturation field
Anisotropy field
Explanation - Coercive force is the field required to demagnetize a material.
Correct answer is: Coercive force
Q.32 Which phenomenon causes a ferromagnetic material to expand when magnetized?
Magnetostriction
Piezoelectric effect
Magnetocaloric effect
Electrostriction
Explanation - Magnetostriction is the strain induced by magnetization.
Correct answer is: Magnetostriction
Q.33 Which magnetic material is best suited for high‑frequency power transformers?
Soft silicon steel
Ferrite core
NdFeB magnet
Alnico alloy
Explanation - Ferrites have low eddy‑current loss at high frequencies.
Correct answer is: Ferrite core
Q.34 In magnetostriction, the relative change in length (ΔL/L) is called:
Magnetostriction coefficient
Magnetoelastic constant
Magnetoresistance
Magnetocaloric coefficient
Explanation - This coefficient quantifies strain per unit magnetic field.
Correct answer is: Magnetostriction coefficient
Q.35 Which of the following is a characteristic of antiferromagnetic materials?
Large net magnetization
Zero net magnetization below Neel temperature
High coercivity
Strong diamagnetism
Explanation - Antiferromagnets have oppositely aligned moments canceling out.
Correct answer is: Zero net magnetization below Neel temperature
Q.36 The 'softness' of a magnetic material is primarily influenced by:
High electrical resistivity
Large grain size
Low magnetic anisotropy
High saturation magnetization
Explanation - Low anisotropy reduces domain wall pinning, making it soft.
Correct answer is: Low magnetic anisotropy
Q.37 Which material is commonly used to make permanent magnets for speakers?
Alnico
Ferrite
NdFeB
Iron‑silicon alloy
Explanation - NdFeB provides strong, stable magnetization needed for speakers.
Correct answer is: NdFeB
Q.38 The energy product (BH)max of a magnet depends on:
Saturation magnetization squared
Coercive force squared
Product of coercivity and remanence
Curie temperature
Explanation - BHmax is roughly Hc × Mr, a measure of magnet's strength.
Correct answer is: Product of coercivity and remanence
Q.39 In a soft magnetic material, the hysteresis loop is narrow because:
High coercivity
Large magnetic anisotropy
Low magnetic loss
High Curie temperature
Explanation - Soft materials have minimal energy dissipation per cycle.
Correct answer is: Low magnetic loss
Q.40 Which of the following is an example of a magnetic anisotropy energy term?
K1 sin^2θ
E = μ0 H·M
σ = ρ v^2
F = ma
Explanation - Anisotropy energy depends on the angle of magnetization relative to easy axis.
Correct answer is: K1 sin^2θ
Q.41 What causes the increase in electrical resistance of a ferromagnetic metal when it becomes magnetized?
Spin‑dependent scattering
Magnetostriction
Magneto‑optical effect
Thermal expansion
Explanation - Alignment of spins increases scattering of conduction electrons.
Correct answer is: Spin‑dependent scattering
Q.42 The magnetization of a material at saturation is usually expressed in:
A/m
T
Wb/m
J/T
Explanation - Saturation magnetization is commonly given in Tesla.
Correct answer is: T
Q.43 Which magnetic material is known for its high coercivity and good thermal stability?
NdFeB
SmCo
Alnico
Ferrite
Explanation - SmCo has higher coercivity and stability compared to NdFeB.
Correct answer is: SmCo
Q.44 In a magnetic sensor using Hall effect, the voltage generated is proportional to:
Current intensity
Magnetic field strength
Temperature
Mechanical strain
Explanation - Hall voltage depends on the magnetic field perpendicular to current flow.
Correct answer is: Magnetic field strength
Q.45 Which of the following is NOT a type of magnetic domain?
Uniform domain
Transverse domain
Vortex domain
Cavity domain
Explanation - Cavity domain is not a recognized domain type.
Correct answer is: Cavity domain
Q.46 A material with negligible hysteresis loss is desirable in:
Permanent magnets
Power transformers
Data storage
Magnetic refrigeration
Explanation - Transformers require low core loss for efficiency.
Correct answer is: Power transformers
Q.47 What is the primary difference between ferrite and soft silicon steel?
Ferrite has higher electrical conductivity
Soft silicon steel has higher magnetic permeability
Ferrite is an oxide ceramic, soft silicon steel is an alloy
Soft silicon steel has higher Curie temperature
Explanation - Ferrites are ceramic oxides, whereas silicon steel is an iron alloy.
Correct answer is: Ferrite is an oxide ceramic, soft silicon steel is an alloy
Q.48 In magnetic recording media, the information is stored in:
The thickness of the film
The direction of magnetization
The electrical resistance
The optical reflectivity
Explanation - Bits are encoded by magnetization orientation.
Correct answer is: The direction of magnetization
Q.49 The magnetic susceptibility of a paramagnetic material varies with temperature as:
T
1/T
T^2
1/T^2
Explanation - Curie’s law states χ = C/T for paramagnets.
Correct answer is: 1/T
Q.50 Which of the following is a common source of magnetic noise in electrical devices?
Eddy currents
Johnson‑Nyquist noise
Spin‑Hall effect
Magnetostatic field fluctuations
Explanation - Eddy currents produce fluctuating magnetic fields, leading to noise.
Correct answer is: Eddy currents
Q.51 Which property of a magnetic material is determined by the number of unpaired electrons per formula unit?
Magnetic anisotropy
Saturation magnetization
Coercivity
Electrical conductivity
Explanation - Saturation magnetization depends on total magnetic moment, related to unpaired electrons.
Correct answer is: Saturation magnetization
Q.52 The phenomenon where a material’s magnetization changes with temperature is called:
Thermal demagnetization
Magnetocaloric effect
Magneto‑thermal effect
Magneto‑optical Kerr effect
Explanation - It refers to temperature change due to magnetic field variation.
Correct answer is: Magnetocaloric effect
Q.53 A hard magnetic material typically has a high ratio of:
Saturation magnetization to Curie temperature
Coercivity to saturation magnetization
Electrical conductivity to resistivity
Magnetic susceptibility to permeability
Explanation - Hard magnets retain magnetization, reflected in high coercivity relative to Ms.
Correct answer is: Coercivity to saturation magnetization
Q.54 Which material is commonly used as a magnetic core for induction coils operating at low frequency?
Ferrite
Soft silicon steel
Alnico
NdFeB
Explanation - Soft silicon steel provides low losses at low frequencies.
Correct answer is: Soft silicon steel
Q.55 What is the main factor that limits the maximum operating temperature of a ferrite core?
Loss of magnetic permeability
Decrease in electrical resistivity
Increase in coercivity
Rise in mechanical strength
Explanation - Ferrite permeability drops sharply above its Curie temperature.
Correct answer is: Loss of magnetic permeability
Q.56 Which of the following is a typical composition for a soft magnetic alloy?
Fe–Si–Al
Fe–Ni–Co
Fe–Mn–Al
Fe–O
Explanation - Iron‑silicon‑aluminum alloys are used for low‑loss soft magnets.
Correct answer is: Fe–Si–Al
Q.57 In a magnetic refrigeration cycle, the material is typically cooled by:
Adiabatic demagnetization
Joule heating
Magnetic induction
Eddy‑current heating
Explanation - Adiabatic demagnetization reduces temperature by removing magnetic field.
Correct answer is: Adiabatic demagnetization
Q.58 The magnetic moment of a single iron atom is approximately:
2 Bohr magnetons
5 Bohr magnetons
1 Bohr magneton
10 Bohr magnetons
Explanation - An iron atom in the ground state has a magnetic moment of about 2 μB.
Correct answer is: 2 Bohr magnetons
Q.59 The demagnetizing factor depends on:
Electrical resistivity
Geometrical shape
Magnetic anisotropy
Curie temperature
Explanation - Demagnetizing factor is determined by the sample’s shape.
Correct answer is: Geometrical shape
Q.60 Which type of magnetic material shows a hysteresis loop with a high remanent magnetization but low coercivity?
Hard magnet
Soft magnet
Paramagnet
Diamagnet
Explanation - Soft magnets have high Mr and low coercivity.
Correct answer is: Soft magnet
Q.61 The product of magnetic permeability (µ) and magnetic field strength (H) yields which physical quantity?
Magnetic flux density (B)
Magnetic susceptibility (χ)
Magnetic energy density
Magnetic charge density
Explanation - B = µH in SI units.
Correct answer is: Magnetic flux density (B)
Q.62 Which of the following is a key advantage of using nanocrystalline magnetic alloys in inductors?
Higher electrical conductivity
Higher saturation magnetization
Lower core loss at high frequency
Higher coercivity
Explanation - Nanocrystalline alloys reduce eddy‑current losses.
Correct answer is: Lower core loss at high frequency
Q.63 A magnetic material with a high saturation magnetization but low coercivity is best described as:
Hard magnetic material
Soft magnetic material
Superconductor
Diamagnet
Explanation - Soft materials have high Ms and low coercivity.
Correct answer is: Soft magnetic material
Q.64 What is the main physical origin of magnetic anisotropy in a crystal?
Spin–orbit coupling
Electron–phonon interaction
Crystal lattice vibrations
Thermal expansion
Explanation - Spin–orbit coupling links magnetic moments to crystal axes.
Correct answer is: Spin–orbit coupling
Q.65 Which effect causes a change in electrical resistance in a ferromagnetic conductor when its magnetization direction is altered?
Hall effect
Anisotropic magnetoresistance (AMR)
Spin Hall effect
Magneto‑optical Kerr effect
Explanation - AMR depends on the angle between current and magnetization.
Correct answer is: Anisotropic magnetoresistance (AMR)
Q.66 Which material is typically used to fabricate high‑strength permanent magnets for wind turbine generators?
Fe–Si alloy
Alnico
NdFeB
Ferrite
Explanation - NdFeB offers high magnetic flux density for large generators.
Correct answer is: NdFeB
Q.67 The maximum energy product of a NdFeB magnet is approximately:
1–2 kJ/m³
10–20 kJ/m³
50–70 kJ/m³
100–150 kJ/m³
Explanation - NdFeB magnets achieve about 50–70 kJ/m³.
Correct answer is: 50–70 kJ/m³
Q.68 The temperature at which a ferromagnetic material loses its spontaneous magnetization is called:
Glass transition temperature
Debye temperature
Curie temperature
Melting point
Explanation - Above Curie temperature, ferromagnetism disappears.
Correct answer is: Curie temperature
Q.69 Which of the following is not a characteristic of ferrimagnetic materials?
Opposite sublattice magnetizations
Net magnetic moment
High saturation magnetization
Zero coercivity
Explanation - Ferrimagnets can have non‑zero coercivity.
Correct answer is: Zero coercivity
Q.70 The magnetization curve of a hard magnetic material shows a wide hysteresis loop mainly because of:
High coercivity
Low magnetic susceptibility
Low saturation magnetization
Large magnetic domains
Explanation - High coercivity causes wide loop.
Correct answer is: High coercivity
Q.71 Which property of a magnetic material is represented by the slope of the initial part of the B-H curve?
Coercive force
Saturation magnetization
Initial permeability
Remanence
Explanation - Slope of initial linear region gives μi.
Correct answer is: Initial permeability
Q.72 In a magnetic recording medium, the minimum bit size that can be recorded is limited by:
Curie temperature
Coercivity
Domain wall width
Saturation magnetization
Explanation - Higher coercivity allows smaller bits without overwriting.
Correct answer is: Coercivity
Q.73 Which effect is exploited in magnetic sensors for detecting velocity of rotating shafts?
Magneto‑optical Kerr effect
Magnetoresistance
Magnetocaloric effect
Hall effect
Explanation - Hall sensors detect rotational speed via induced voltage.
Correct answer is: Hall effect
Q.74 A magnetic material with a large magnetostrictive coefficient is useful for:
Electrical insulation
Actuators and sensors
Superconducting magnets
Optical fibers
Explanation - Large magnetostriction yields high strain for actuation.
Correct answer is: Actuators and sensors
Q.75 What determines the frequency at which core losses in a ferrite material become significant?
Electrical resistivity
Curie temperature
Magnetostriction coefficient
Grain size
Explanation - Lower resistivity increases eddy‑current loss at higher frequencies.
Correct answer is: Electrical resistivity
Q.76 Which of the following magnetic phenomena occurs when a paramagnetic material is placed in a non‑uniform magnetic field?
Magnetic levitation
Magnetic attraction
Magnetic repulsion
Magnetic torque
Explanation - Paramagnets are attracted to strong magnetic field regions.
Correct answer is: Magnetic attraction
Q.77 The ratio of magnetic anisotropy energy to Zeeman energy determines:
Magnetic domain size
Coercivity
Saturation magnetization
Remanence
Explanation - High anisotropy energy increases coercivity.
Correct answer is: Coercivity
Q.78 Which of the following materials is NOT typically used as a permanent magnet?
Alnico
Ferrite
Graphite
NdFeB
Explanation - Graphite is non‑magnetic and cannot be a permanent magnet.
Correct answer is: Graphite
Q.79 In a soft magnetic material, the energy loss per cycle is mainly due to:
Joule heating
Hysteresis loss
Eddy‑current loss
Spin‑orbit coupling
Explanation - Soft materials still lose energy due to domain wall motion.
Correct answer is: Hysteresis loss
Q.80 The magnetization of a material in a magnetic field is governed by which of the following laws?
Hooke's law
Coulomb's law
Curie's law
Faraday's law
Explanation - Curie's law relates magnetization to inverse temperature for paramagnets.
Correct answer is: Curie's law
Q.81 Which factor does NOT influence the coercivity of a hard magnetic alloy?
Grain size
Magnetic anisotropy
Electrical resistivity
Chemical composition
Explanation - Resistivity does not directly affect coercivity.
Correct answer is: Electrical resistivity
Q.82 Which type of magnetic material exhibits a hysteresis loop that closes at zero field without remanence?
Hard magnet
Soft magnet
Paramagnet
Diamagnet
Explanation - Soft magnets have negligible remanence.
Correct answer is: Soft magnet
Q.83 In a magnetic core, what is the primary cause of eddy‑current loss?
Magnetic domain wall motion
Induced voltage in closed loops
Magnetization reversal
Spin‑flip scattering
Explanation - Changing flux induces circulating currents, causing loss.
Correct answer is: Induced voltage in closed loops
Q.84 A magnetic material with high saturation magnetization and high coercivity is used as a:
Soft magnetic core
Hard magnetic permanent magnet
Eddy‑current shield
Magnetic sensor
Explanation - Hard magnets retain high magnetization.
Correct answer is: Hard magnetic permanent magnet
Q.85 Which of the following is a measure of the ease of aligning magnetic moments in a material?
Curie temperature
Magnetic susceptibility
Saturation magnetization
Coercivity
Explanation - Susceptibility indicates how easily a material becomes magnetized.
Correct answer is: Magnetic susceptibility
Q.86 The phenomenon where a magnetic material loses its magnetization after being exposed to high temperature is known as:
Eddy‑current demagnetization
Thermal demagnetization
Magnetostatic decay
Magneto‑optical loss
Explanation - Heat can exceed Curie temperature, destroying magnetization.
Correct answer is: Thermal demagnetization
Q.87 Which of these is a common application of magnetostrictive sensors?
Temperature measurement
Speed detection
Pressure monitoring
Light intensity measurement
Explanation - Magnetostrictive sensors convert magnetic changes to strain signals, used in speedometers.
Correct answer is: Speed detection
Q.88 In a permanent magnet, the remanent magnetization (Mr) is typically:
Zero
Equal to saturation magnetization
Greater than saturation magnetization
Less than saturation magnetization
Explanation - Remanence is the remaining magnetization after removing field.
Correct answer is: Less than saturation magnetization
Q.89 The term 'magnetic domains' refers to:
Regions with uniform magnetization direction
Areas of electrical resistivity
Zones with different crystal structures
Regions with different temperatures
Explanation - Domains are small regions where spins are aligned.
Correct answer is: Regions with uniform magnetization direction
Q.90 Which material has the highest intrinsic magnetic permeability at room temperature?
Pure iron
Silicon steel
Ferrite
Alnico
Explanation - Pure iron has the highest permeability among common magnetic materials.
Correct answer is: Pure iron
Q.91 The energy density stored in a magnetic core is proportional to:
μ H^2
μ M_s^2
σ H
ρ E^2
Explanation - Magnetic energy density is (1/2) μ H^2.
Correct answer is: μ H^2
Q.92 Which property of a magnetic material is determined by the number of electrons in the outer shell?
Saturation magnetization
Magnetic susceptibility
Curie temperature
Electrical resistivity
Explanation - Outer electrons contribute to magnetic moment.
Correct answer is: Saturation magnetization
Q.93 The term 'soft magnetic' is used for materials with:
High coercivity
Low coercivity
High saturation magnetization only
Low electrical resistivity
Explanation - Soft magnets can be magnetized/demagnetized easily.
Correct answer is: Low coercivity
Q.94 A magnetic sensor that uses a piezoelectric crystal in a magnetic field to detect strain is called a:
Hall sensor
Fluxgate sensor
Piezo‑magnetometer
Magnetostrictive sensor
Explanation - It measures strain from magnetostrictive effects.
Correct answer is: Magnetostrictive sensor
Q.95 In a magnetically anisotropic material, the energy required to rotate magnetization by an angle θ is given by:
E = K sin^2θ
E = K cos^2θ
E = K θ
E = K θ^2
Explanation - Anisotropy energy depends on sin^2θ for uniaxial anisotropy.
Correct answer is: E = K sin^2θ
Q.96 The magnetic field produced by a permanent magnet is called the:
Flux density
Magnetic flux
Magnetic field
Induced voltage
Explanation - Permanent magnets generate a magnetic field (B or H).
Correct answer is: Magnetic field
Q.97 Which of the following materials has a negative magnetic susceptibility?
Alnico
NdFeB
Ferrite
Graphite
Explanation - Graphite is diamagnetic with negative susceptibility.
Correct answer is: Graphite
Q.98 Which of the following is a measure of how much a material resists changes in its magnetic state?
Coercivity
Curie temperature
Saturation magnetization
Magnetic permeability
Explanation - Coercivity quantifies resistance to demagnetization.
Correct answer is: Coercivity
Q.99 Which property of a material increases with decreasing grain size in magnetic alloys?
Coercivity
Curie temperature
Saturation magnetization
Electrical conductivity
Explanation - Smaller grains impede domain wall motion, raising coercivity.
Correct answer is: Coercivity
Q.100 Which of the following is NOT a source of core loss in magnetic cores?
Eddy currents
Hysteresis loss
Magnetostriction loss
Thermal conduction loss
Explanation - Core loss arises from electromagnetic effects, not thermal conduction.
Correct answer is: Thermal conduction loss
Q.101 The magnetic field at the center of a solenoid is proportional to:
Number of turns per length × current
Resistance × current
Capacitance × current
Frequency × resistance
Explanation - B = μ₀ n I for a solenoid.
Correct answer is: Number of turns per length × current
Q.102 Which of the following phenomena explains why a ferromagnetic material exhibits hysteresis?
Domain wall pinning
Eddy‑current heating
Spin‑orbit coupling
Magnetostriction
Explanation - Pinning of domain walls leads to energy loss and hysteresis.
Correct answer is: Domain wall pinning
Q.103 Which material is widely used in the cores of high‑frequency transformers due to its high resistivity?
Ferrite
Silicon steel
Alnico
NdFeB
Explanation - Ferrite's high resistivity reduces eddy‑current losses at high frequencies.
Correct answer is: Ferrite
Q.104 The magnetic anisotropy energy of a cubic crystal depends on which angles?
Angles between magnetization and crystal axes
Angles between domains
Angles between electric field and magnetic field
Angles between current and magnetic field
Explanation - Anisotropy energy depends on relative orientation to crystal lattice.
Correct answer is: Angles between magnetization and crystal axes
Q.105 Which of the following is a characteristic of a paramagnetic material?
Non‑zero remanence
High coercivity
Magnetization proportional to magnetic field
Negative magnetic permeability
Explanation - Paramagnets exhibit linear magnetization with field.
Correct answer is: Magnetization proportional to magnetic field
Q.106 The phenomenon where a magnetic material’s magnetization decreases with increasing temperature follows which law for paramagnets?
Ohm's law
Curie's law
Newton's law
Hooke's law
Explanation - Curie's law states χ = C/T for paramagnetics.
Correct answer is: Curie's law
Q.107 Which of the following materials is known for having the highest magnetic permeability at low frequencies?
Pure iron
Alnico
NdFeB
Graphite
Explanation - Pure iron offers the highest low‑frequency permeability.
Correct answer is: Pure iron
Q.108 In magnetic recording, the term 'bit density' refers to:
Number of bits per unit area of magnetic medium
Number of bits per unit time
Number of bits per unit volume
Number of bits per unit length
Explanation - Bit density is bits per square inch or mm².
Correct answer is: Number of bits per unit area of magnetic medium
Q.109 Which property of a magnetic material is most critical for use in a transformer core?
High saturation magnetization
High coercivity
Low core loss
High electrical conductivity
Explanation - Low core loss ensures high efficiency in transformers.
Correct answer is: Low core loss
Q.110 A magnetic field applied perpendicular to a ferromagnetic slab causes a change in its dimensions due to:
Eddy currents
Magnetostriction
Magneto‑optical effect
Thermal expansion
Explanation - Magnetostriction leads to dimensional change under a field.
Correct answer is: Magnetostriction
Q.111 The process of aligning magnetic domains by applying a strong magnetic field is called:
Saturation
Demagnetization
Annealing
Compensation
Explanation - Saturation occurs when all domains are aligned.
Correct answer is: Saturation
Q.112 Which of the following materials exhibits the highest coercivity among common permanent magnets?
NdFeB
Alnico
Ferrite
SmCo
Explanation - SmCo magnets have the highest coercivity values.
Correct answer is: SmCo
Q.113 A magnetic field that opposes the applied field in a material is characteristic of:
Diamagnetism
Paramagnetism
Ferromagnetism
Antiferromagnetism
Explanation - Diamagnetic materials produce a field opposite to the applied one.
Correct answer is: Diamagnetism
Q.114 The change in magnetic energy stored in a material due to a change in magnetic field is called:
Magnetic work
Magnetic potential
Magnetic flux
Magnetic field energy
Explanation - Work is done when magnetic flux changes in the presence of magnetization.
Correct answer is: Magnetic work
Q.115 In a magnetic sensor using Hall effect, the output voltage is proportional to:
Magnetic field strength × current × sample thickness
Magnetic field strength × resistivity
Magnetic field strength × temperature
Magnetic field strength × magnetization
Explanation - Hall voltage V = (B I t)/ (n e d) for a conductor.
Correct answer is: Magnetic field strength × current × sample thickness
Q.116 Which of the following is a characteristic of a soft magnetic material?
High remanence
Low coercivity
High saturation magnetization
High Curie temperature
Explanation - Soft magnets can be magnetized and demagnetized easily.
Correct answer is: Low coercivity
Q.117 The temperature at which a ferromagnet loses its spontaneous magnetization is known as:
Curie temperature
Debye temperature
Glass transition temperature
Neel temperature
Explanation - Above Curie temperature, the material becomes paramagnetic.
Correct answer is: Curie temperature
Q.118 In a magnetic core, increasing the frequency of the applied magnetic field typically leads to:
Reduced core loss
Increased core loss
No change in core loss
Zero core loss
Explanation - Core loss generally rises with frequency due to eddy currents and hysteresis.
Correct answer is: Increased core loss
Q.119 Which of the following is NOT a typical composition of a ferrite used in high‑frequency applications?
MnZn
NiZn
CoFe2O4
CuFe2O4
Explanation - CuFe2O4 is not a common high‑frequency ferrite.
Correct answer is: CuFe2O4
Q.120 The energy lost per cycle due to hysteresis in a magnetic material is proportional to:
The area of the hysteresis loop
The peak magnetic field
The electrical resistivity
The temperature
Explanation - The loop area equals energy loss per cycle.
Correct answer is: The area of the hysteresis loop
Q.121 A permanent magnet made from NdFeB has a high coercivity primarily because of:
High electrical conductivity
Large magnetic anisotropy energy
High saturation magnetization
Low Curie temperature
Explanation - Large anisotropy provides resistance to demagnetization.
Correct answer is: Large magnetic anisotropy energy
Q.122 Which material is commonly used as a core for low‑frequency transformers?
Ferrite
Soft silicon steel
NdFeB
Alnico
Explanation - Soft silicon steel has low losses at low frequencies.
Correct answer is: Soft silicon steel
Q.123 What is the term for the resistance of a magnetic material to changes in magnetization direction?
Coercivity
Magnetic viscosity
Magnetic susceptibility
Magnetic permeability
Explanation - Coercivity measures the field needed to reduce magnetization to zero.
Correct answer is: Coercivity
Q.124 The phenomenon in which a ferromagnet’s magnetization reduces when the material is heated is called:
Thermal demagnetization
Magnetization reversal
Magnetocaloric effect
Eddy‑current loss
Explanation - Heating can reduce or eliminate magnetization.
Correct answer is: Thermal demagnetization
Q.125 Which of the following materials has the highest magnetic domain wall energy?
NdFeB
Alnico
Ferrite
Pure iron
Explanation - NdFeB has high anisotropy, leading to higher domain wall energy.
Correct answer is: NdFeB
Q.126 Which of the following is a common source of noise in magnetic sensors?
Thermal fluctuations
Eddy currents
Photon scattering
Acoustic vibrations
Explanation - Thermal noise affects magnetization orientation.
Correct answer is: Thermal fluctuations
Q.127 The term 'magnetostriction' refers to:
Change in temperature with magnetic field
Change in magnetization with temperature
Change in electrical conductivity with field
Change in shape or dimensions due to magnetization
Explanation - Magnetostriction is the strain resulting from magnetic ordering.
Correct answer is: Change in shape or dimensions due to magnetization
Q.128 A magnetic material that exhibits no hysteresis loss and can be easily magnetized and demagnetized is known as a:
Hard magnet
Soft magnet
Paramagnet
Diamagnet
Explanation - Soft magnets have negligible hysteresis loss.
Correct answer is: Soft magnet
Q.129 Which of the following is a typical application of magnetic refrigeration?
Air conditioning
Food preservation
Magnetic levitation
Electric power generation
Explanation - Magnetocaloric refrigerators can cool food products.
Correct answer is: Food preservation
Q.130 The property that measures a material's ability to store magnetic energy is known as:
Coercivity
Magnetic permeability
Magnetic energy density
Magnetic susceptibility
Explanation - Energy density indicates how much magnetic energy a material can contain.
Correct answer is: Magnetic energy density
Q.131 Which of the following materials is known for its high coercivity and good thermal stability at elevated temperatures?
NdFeB
SmCo
Alnico
Ferrite
Explanation - SmCo magnets retain high coercivity even at high temperatures.
Correct answer is: SmCo
Q.132 In a magnetic core, the demagnetizing field opposes the applied magnetic field due to:
Electrical resistance
Magnetic anisotropy
Magnetic dipole interactions
Thermal expansion
Explanation - Magnetic dipoles create a field opposing external fields.
Correct answer is: Magnetic dipole interactions
Q.133 Which of the following is a characteristic of a magnetic material that has a high Curie temperature?
It loses magnetization at low temperatures
It remains magnetically ordered up to high temperatures
It exhibits large hysteresis loss
It has low saturation magnetization
Explanation - High Curie temperature means the material stays ferromagnetic at higher temperatures.
Correct answer is: It remains magnetically ordered up to high temperatures
Q.134 The phenomenon of a material developing a magnetic field opposite to an applied external field is called:
Magnetization
Diamagnetism
Ferromagnetism
Paramagnetism
Explanation - Diamagnetism produces a negative magnetic field relative to the applied one.
Correct answer is: Diamagnetism
Q.135 Which of the following is NOT typically a constituent of a ferrite used in inductors?
Fe
Zn
Ni
Cu
Explanation - Copper is not a standard component in ferrites for inductors.
Correct answer is: Cu
Q.136 The energy lost due to domain wall motion during magnetization reversal is called:
Eddy‑current loss
Hysteresis loss
Magnetostriction loss
Curie loss
Explanation - Domain wall motion causes hysteresis loss.
Correct answer is: Hysteresis loss
Q.137 The property that describes how quickly a magnetic material can respond to changes in the external magnetic field is:
Magnetic susceptibility
Magnetic permeability
Magnetic damping
Magnetic resonance
Explanation - Magnetic damping reflects the speed of response.
Correct answer is: Magnetic damping
Q.138 Which of the following best describes the relationship between magnetic field (H) and magnetic flux density (B) in a linear material?
B = µ0H
B = µ0µrH
B = µrH
B = H/µ0
Explanation - In linear media, B is proportional to H via permeability.
Correct answer is: B = µ0µrH
Q.139 A permanent magnet made from Alnico is often chosen for:
High temperature applications
Low coercivity requirements
Low cost
High magnetic flux density
Explanation - Alnico magnets are relatively inexpensive compared to rare‑earth magnets.
Correct answer is: Low cost
Q.140 In magnetic refrigeration, the material is cooled by:
Applying a magnetic field
Removing a magnetic field
Passing a current through it
Increasing temperature
Explanation - Adiabatic demagnetization cools the material.
Correct answer is: Removing a magnetic field
Q.141 Which property is directly related to the number of unpaired electrons in an atom?
Curie temperature
Magnetic permeability
Saturation magnetization
Coercivity
Explanation - Saturation magnetization depends on unpaired electron count.
Correct answer is: Saturation magnetization
Q.142 Which type of magnetic material is typically used in read heads of hard disk drives?
Soft magnetic alloy
Hard magnetic alloy
Ferromagnetic metal
Ferrite ceramic
Explanation - Soft magnetic alloys provide high permeability and low loss for read heads.
Correct answer is: Soft magnetic alloy
Q.143 The amount of magnetic flux that can pass through a material per unit area is called:
Magnetic field strength
Magnetic flux density
Magnetic permeability
Magnetic energy density
Explanation - Flux density (B) measures flux per unit area.
Correct answer is: Magnetic flux density
Q.144 The temperature dependence of magnetic susceptibility in a paramagnet is described by:
χ = C/T
χ = C*T
χ = C/T^2
χ = C*log(T)
Explanation - Curie’s law gives χ proportional to 1/T.
Correct answer is: χ = C/T
Q.145 Which property is NOT a key parameter for a magnetic core used in transformers?
Saturation flux density
Coercivity
Curie temperature
Electrical resistivity
Explanation - Low coercivity is desired but not a primary core parameter.
Correct answer is: Coercivity
Q.146 The term 'remanent magnetization' refers to:
Magnetization after cooling
Magnetization after applying a field and removing it
Magnetization under constant field
Magnetization in the presence of temperature gradient
Explanation - Remanence is the residual magnetization after field removal.
Correct answer is: Magnetization after applying a field and removing it
Q.147 Which phenomenon explains why a ferromagnet’s magnetization can be switched by a small external field?
Magnetic domain wall motion
Eddy currents
Spin‑orbit coupling
Magnetostriction
Explanation - Domain walls move, changing net magnetization.
Correct answer is: Magnetic domain wall motion
Q.148 What is the main advantage of using high‑resistivity materials for magnetic cores in AC applications?
Reduced eddy‑current loss
Increased permeability
Lower cost
Higher saturation magnetization
Explanation - Higher resistivity suppresses eddy currents, decreasing loss.
Correct answer is: Reduced eddy‑current loss
Q.149 The product of magnetic field strength (H) and magnetic flux density (B) is proportional to:
Magnetic energy density
Magnetic pressure
Magnetic temperature
Magnetic resistivity
Explanation - Energy density is (1/2) BH for linear media.
Correct answer is: Magnetic energy density
Q.150 Which of the following is a characteristic of a diamagnetic material?
Positive magnetization
Negative magnetization relative to applied field
Remanent magnetization
Large coercivity
Explanation - Diamagnetism opposes external fields.
Correct answer is: Negative magnetization relative to applied field
Q.151 The saturation magnetization of a material can be increased by:
Increasing grain size
Reducing temperature
Adding non‑magnetic impurities
Applying high pressure
Explanation - Lower temperatures reduce thermal agitation, increasing Ms.
Correct answer is: Reducing temperature
Q.152 The main difference between a soft and a hard magnetic material is:
Saturation magnetization
Curie temperature
Coercivity
Electrical resistivity
Explanation - Soft magnets have low coercivity; hard magnets have high coercivity.
Correct answer is: Coercivity
Q.153 Which property of a ferromagnet is measured by the area enclosed in its B-H hysteresis loop?
Energy loss per cycle
Saturation magnetization
Curie temperature
Coercivity
Explanation - The loop area quantifies energy loss during a cycle.
Correct answer is: Energy loss per cycle
Q.154 Which type of magnetic material is best suited for high‑power applications due to its high saturation flux density?
Ferrite
NdFeB
Alnico
Silicon steel
Explanation - NdFeB has high saturation flux density, suitable for power devices.
Correct answer is: NdFeB
Q.155 Which phenomenon causes a magnetic material to generate an electric voltage when its magnetization changes?
Faraday's law of induction
Hall effect
Magnetostriction
Spin Hall effect
Explanation - Changing magnetic flux induces voltage.
Correct answer is: Faraday's law of induction
Q.156 The term 'magnetic permeability' (µ) is the ratio of:
Magnetic field strength to flux density
Flux density to magnetic field strength
Magnetization to applied field
Energy density to field strength
Explanation - µ = B/H, a measure of how a material responds to a magnetic field.
Correct answer is: Flux density to magnetic field strength
Q.157 What is the primary function of a magnetic shield?
To generate a magnetic field
To block external magnetic fields
To amplify magnetic signals
To increase eddy currents
Explanation - A shield attenuates magnetic flux from affecting a device.
Correct answer is: To block external magnetic fields
Q.158 Which property of a magnet dictates the maximum achievable magnetic flux density at a given field strength?
Saturation magnetization
Curie temperature
Coercivity
Anisotropy energy
Explanation - Saturation magnetization limits maximum B achievable.
Correct answer is: Saturation magnetization
Q.159 A material that is strongly attracted to a magnetic field but has negligible remanence is classified as a:
Hard magnet
Soft magnet
Paramagnet
Diamagnet
Explanation - Soft magnets are strongly attracted but lose magnetization when field removed.
Correct answer is: Soft magnet
Q.160 Which of the following is a common technique for measuring the magnetization curve of a material?
SQUID magnetometry
X‑ray diffraction
Electron microscopy
Thermogravimetric analysis
Explanation - SQUIDs provide high‑sensitivity magnetization measurements.
Correct answer is: SQUID magnetometry
Q.161 In the context of magnetic materials, 'magnetic damping' refers to:
Loss of magnetic energy due to eddy currents
Energy loss due to domain wall motion
Resistance to changes in magnetization direction
Resonant absorption of magnetic energy
Explanation - Damping is the dissipation of magnetic energy as domain walls move.
Correct answer is: Energy loss due to domain wall motion
Q.162 The hysteresis loss in a magnetic core is minimized by:
Using high‑resistivity materials
Increasing the core's temperature
Reducing the core's size
Increasing the magnetic field strength
Explanation - High resistivity reduces eddy‑current loss, lowering hysteresis loss.
Correct answer is: Using high‑resistivity materials
Q.163 Which of the following materials typically exhibits the lowest coercivity?
NdFeB
SmCo
Ferrite
Alnico
Explanation - Alnico has relatively low coercivity among permanent magnets.
Correct answer is: Alnico
Q.164 The term 'saturation flux density' refers to:
Maximum magnetic flux density a material can achieve
Minimum magnetic flux density of a material
Flux density at zero field
Flux density at Curie temperature
Explanation - Saturation flux density is the point where B no longer increases with H.
Correct answer is: Maximum magnetic flux density a material can achieve
Q.165 Which property is primarily responsible for a material's magnetic hardness?
Coercivity
Magnetic susceptibility
Curie temperature
Saturation magnetization
Explanation - High coercivity indicates a hard magnetic material.
Correct answer is: Coercivity
Q.166 The phenomenon where a magnetic material loses its magnetization when heated above a certain temperature is called:
Curie transition
Magnetocaloric effect
Eddy‑current heating
Spin‑flip scattering
Explanation - Above the Curie temperature, spontaneous magnetization disappears.
Correct answer is: Curie transition
Q.167 A high‑permeability magnetic material used in transformer cores should have:
High coercivity
Low coercivity
High saturation flux density
High electrical resistivity
Explanation - Low coercivity minimizes core loss and allows easy magnetization.
Correct answer is: Low coercivity
Q.168 Which of the following is NOT a type of magnetic anisotropy?
Shape anisotropy
Magnetocrystalline anisotropy
Stress anisotropy
Temperature anisotropy
Explanation - Temperature does not define anisotropy.
Correct answer is: Temperature anisotropy
Q.169 Which of the following best describes a 'soft' magnetic material?
High coercivity and high remanence
Low coercivity and low remanence
High Curie temperature
Large magnetic anisotropy energy
Explanation - Soft magnets can be easily magnetized and demagnetized.
Correct answer is: Low coercivity and low remanence
Q.170 The 'magnetostatic field' inside a magnetized body is also known as:
External field
Induced field
Demagnetizing field
Internal field
Explanation - Magnetostatic field refers to the field within the material.
Correct answer is: Internal field
Q.171 A material that exhibits a high remanent magnetization but low coercivity is used in:
Permanent magnets
Magnetic shielding
Magnetic recording heads
Magnetic sensors
Explanation - High remanence with low coercivity helps in recording technologies.
Correct answer is: Magnetic recording heads
Q.172 The product of the magnetic field strength (H) and the magnetization (M) is proportional to:
Magnetic energy density
Magnetic pressure
Magnetic flux density
Magnetic permeability
Explanation - Energy density involves the product H·M.
Correct answer is: Magnetic energy density
Q.173 The magnetic field generated by a permanent magnet is described by which equation?
B = μ0H
B = μ0μrH
B = μ0M
B = μ0H + M
Explanation - In a magnetic material, B = μ0(1 + χ)H = μ0μrH.
Correct answer is: B = μ0μrH
Q.174 Which of the following materials is NOT typically used in magnetic cores for AC devices?
Soft silicon steel
Ferrite
Alnico
NdFeB
Explanation - NdFeB has high losses in AC due to eddy currents and is unsuitable for cores.
Correct answer is: NdFeB
Q.175 In magnetic refrigeration, the 'adiabatic demagnetization' process results in:
Temperature increase
Temperature decrease
No temperature change
Increase in magnetic field
Explanation - Removing the field adiabatically cools the material.
Correct answer is: Temperature decrease
Q.176 The characteristic property of a material that defines the ease of magnetization is called:
Coercivity
Magnetic permeability
Curie temperature
Saturation magnetization
Explanation - Permeability indicates how easily a material can be magnetized.
Correct answer is: Magnetic permeability
Q.177 Which of the following is the main cause of core loss in a magnetic material?
Magnetostriction
Eddy currents
Thermal expansion
Magnetic anisotropy
Explanation - Eddy currents cause energy loss in alternating magnetic fields.
Correct answer is: Eddy currents
Q.178 In a ferromagnetic material, the direction of spontaneous magnetization is referred to as the:
Hard axis
Easy axis
Intermediate axis
Random axis
Explanation - The easy axis is the direction of lowest energy for magnetization.
Correct answer is: Easy axis
Q.179 Which of the following is a typical application of ferrite materials?
Magnetic recording heads
Transformers for power supplies
Magnetic refrigeration
Permanent magnets for motors
Explanation - Ferrites are widely used in transformer cores due to low loss.
Correct answer is: Transformers for power supplies
Q.180 The term 'remanence' refers to:
Magnetic field inside a core
Residual magnetization after removal of external field
Change in magnetic susceptibility with temperature
Loss of magnetic energy during reversal
Explanation - Remanence is the remaining magnetization after the external field is removed.
Correct answer is: Residual magnetization after removal of external field
Q.181 In a magnetic material, the energy required to rotate magnetization by an angle θ in an anisotropic crystal is:
E = K sin^2θ
E = K cos^2θ
E = K θ
E = K θ^2
Explanation - Anisotropy energy follows sin^2θ dependence for uniaxial anisotropy.
Correct answer is: E = K sin^2θ