Magnetic domains in a ferromagnetic material are

 

651. Magnetic domains in a ferromagnetic material are
A) Small regions with aligned magnetic moments
B) Randomly oriented regions
C) Non-magnetic regions
D) Conductive regions
Ans: A

652. Soft magnetic materials are characterized by
A) Low coercivity and narrow hysteresis loop
B) High coercivity and wide hysteresis loop
C) Zero permeability
D) High resistivity
Ans: A

653. Hard magnetic materials are used for
A) Permanent magnets
B) Transformer cores
C) Electromagnets
D) Switches
Ans: A

654. Hysteresis loss in magnetic materials is proportional to
A) Frequency of magnetization and area of B-H loop
B) Only frequency
C) Only voltage
D) Only current
Ans: A

655. Curie temperature of iron is approximately
A) 770°C
B) 500°C
C) 1000°C
D) 870°C
Ans: A

656. Permeability of a material is defined as
A) Ratio of B to H
B) Ratio of H to B
C) Magnetic flux density
D) Coercivity
Ans: A

657. Diamagnetic materials have
A) Small negative susceptibility
B) Small positive susceptibility
C) Large positive susceptibility
D) Zero susceptibility
Ans: A

658. Paramagnetic materials have
A) Small positive susceptibility
B) Small negative susceptibility
C) Large negative susceptibility
D) Zero susceptibility
Ans: A

659. Retentivity is the ability of a material to
A) Retain magnetization after removal of field
B) Conduct electricity
C) Resist current flow
D) Store electric energy
Ans: A

660. Coercivity is
A) Reverse magnetic field required to reduce magnetization to zero
B) Magnetic flux
C) Electric field strength
D) Conductivity
Ans: A

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661. Eddy currents in transformer cores can be reduced by
A) Laminating the core
B) Using solid cores
C) Increasing current
D) Reducing voltage
Ans: A

662. Soft ferrites are commonly used for
A) High-frequency transformer cores
B) Permanent magnets
C) Electromagnets
D) Conductors
Ans: A

663. Hard ferrites are used for
A) Permanent magnets
B) Transformer cores
C) High-frequency applications
D) Switches
Ans: A

664. Dielectric materials store energy in the form of
A) Electric field
B) Magnetic field
C) Thermal energy
D) Mechanical energy
Ans: A

665. Dielectric strength is defined as
A) Maximum electric field a material can withstand without breakdown
B) Resistance of a material
C) Conductivity of a material
D) Permittivity
Ans: A

666. The dielectric constant of vacuum is
A) 1
B) 2
C) 3
D) 0
Ans: A

667. Mica is used in capacitors because of
A) High dielectric strength
B) High conductivity
C) Low resistivity
D) Ferromagnetic property
Ans: A

668. Quartz is used in oscillators due to
A) Piezoelectric effect
B) Magnetic effect
C) Thermal conductivity
D) Conductivity
Ans: A

669. Piezoelectric materials generate voltage when
A) Mechanical stress is applied
B) Temperature is increased
C) Magnetic field is applied
D) Voltage is applied
Ans: A

670. Band gap of silicon at 300 K is
A) 1.1 eV
B) 0.72 eV
C) 1.43 eV
D) 2 eV
Ans: A

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671. Band gap of germanium is
A) 0.72 eV
B) 1.1 eV
C) 1.43 eV
D) 2 eV
Ans: A

672. Intrinsic semiconductors have
A) Equal number of electrons and holes
B) More electrons than holes
C) More holes than electrons
D) No carriers
Ans: A

673. N-type semiconductors have
A) Electrons as majority carriers
B) Holes as majority carriers
C) Neutral carriers
D) No carriers
Ans: A

674. P-type semiconductors have
A) Holes as majority carriers
B) Electrons as majority carriers
C) Neutral carriers
D) No carriers
Ans: A

675. The intrinsic carrier concentration of silicon at 300 K is approximately
A) 1.5×10¹⁰ cm⁻³
B) 2.5×10¹³ cm⁻³
C) 10¹² cm⁻³
D) 10⁸ cm⁻³
Ans: A

676. Doping a semiconductor increases
A) Carrier concentration
B) Band gap
C) Resistivity
D) Coercivity
Ans: A

677. Donor impurities in silicon create
A) N-type semiconductor
B) P-type semiconductor
C) Insulator
D) Conductor
Ans: A

678. Acceptor impurities in silicon create
A) P-type semiconductor
B) N-type semiconductor
C) Conductor
D) Insulator
Ans: A

679. Hall effect can be used to determine
A) Type of semiconductor
B) Carrier concentration
C) Magnetic field
D) All of these
Ans: D

680. Drift current in a semiconductor depends on
A) Carrier concentration, mobility, and electric field
B) Only electric field
C) Temperature
D) Material density
Ans: A

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681. Diffusion current in a semiconductor occurs due to
A) Carrier concentration gradient
B) Electric field
C) Magnetic field
D) Pressure
Ans: A

682. Electron mobility in silicon at 300 K is approximately
A) 1350 cm²/V·s
B) 450 cm²/V·s
C) 1000 cm²/V·s
D) 1500 cm²/V·s
Ans: A

683. Hole mobility in silicon at 300 K is approximately
A) 450 cm²/V·s
B) 1350 cm²/V·s
C) 800 cm²/V·s
D) 2000 cm²/V·s
Ans: A

684. The resistivity of metals increases with
A) Temperature
B) Decrease in temperature
C) Constant temperature
D) Magnetic field
Ans: A

685. The resistivity of semiconductors decreases with
A) Increase in temperature
B) Decrease in temperature
C) Constant temperature
D) Pressure
Ans: A

686. Thermal conductivity of metals is mainly due to
A) Free electrons
B) Phonons
C) Lattice vibrations
D) Ions
Ans: A

687. Electrical strain gauges work on the principle of
A) Variation of resistance with strain
B) Piezoelectric effect
C) Magnetic effect
D) Thermal conductivity
Ans: A

688. Electrical conductivity σ and resistivity ρ are related by
A) σ = 1/ρ
B) σ = ρ
C) σ = ρ²
D) σ = √ρ
Ans: A

689. Retentivity is
A) Ability to retain magnetization
B) Ability to resist current
C) Permeability
D) Susceptibility
Ans: A

690. Coercivity is
A) Reverse field required to demagnetize
B) Permeability
C) Flux density
D) Conductivity
Ans: A

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691. Soft magnetic materials have
A) Low coercivity
B) High coercivity
C) High resistivity
D) Low permeability
Ans: A

692. Hard magnetic materials have
A) High coercivity
B) Low coercivity
C) Zero permeability
D) Low resistivity
Ans: A

693. Ferrites are
A) Ceramic magnetic materials
B) Metallic conductors
C) Semiconductors
D) Insulators only
Ans: A

694. Soft ferrites are used for
A) High-frequency transformer cores
B) Permanent magnets
C) Switches
D) Motors
Ans: A

695. Hard ferrites are used for
A) Permanent magnets
B) Transformer cores
C) High-frequency applications
D) Conductors
Ans: A

696. Dielectric materials store energy in the form of
A) Electric field
B) Magnetic field
C) Thermal energy
D) Mechanical energy
Ans: A

697. Mica is used in capacitors because of
A) High dielectric strength
B) High conductivity
C) Low resistivity
D) Ferromagnetic property
Ans: A

698. Quartz is used in oscillators because of
A) Piezoelectric effect
B) Magnetic effect
C) Thermal property
D) Conductivity
Ans: A

699. Piezoelectric materials generate voltage when subjected to
A) Mechanical stress
B) Heat
C) Electric current
D) Magnetic field
Ans: A

700. Band gap of silicon at 300 K is approximately
A) 1.1 eV
B) 0.72 eV
C) 1.43 eV
D) 2 eV
Ans: A