ADVANCE ELECTRICAL MATERIALS MCQS

 551. The energy band gap of intrinsic silicon is approximately

A) 1.1 eV
B) 0.7 eV
C) 1.43 eV
D) 2 eV
Ans: A

552. The energy gap of germanium is
A) 0.72 eV
B) 1.1 eV
C) 1.4 eV
D) 3 eV
Ans: A

553. The conduction in metals is mainly due to
A) Free electrons
B) Ions
C) Holes
D) Neutrons
Ans: A

554. 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

555. In an n-type semiconductor, majority carriers are
A) Electrons
B) Holes
C) Ions
D) Both
Ans: A

556. In a p-type semiconductor, minority carriers are
A) Electrons
B) Holes
C) Ions
D) Neutrons
Ans: A

557. The Hall effect is used to measure
A) Magnetic field
B) Current
C) Voltage
D) Resistance
Ans: A

558. The Hall coefficient of n-type silicon is
A) Negative
B) Positive
C) Zero
D) Infinity
Ans: A

559. The Hall coefficient of p-type silicon is
A) Positive
B) Negative
C) Zero
D) Infinite
Ans: A

560. The resistivity of pure copper at 20°C is about
A) 1.7×10⁻⁸ Ω·m
B) 2.7×10⁻⁸ Ω·m
C) 1×10⁻⁶ Ω·m
D) 10⁻⁵ Ω·m
Ans: A

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561. The resistivity of aluminum at 20°C is approximately
A) 2.7×10⁻⁸ Ω·m
B) 1.7×10⁻⁸ Ω·m
C) 3×10⁻⁶ Ω·m
D) 1×10⁻⁷ Ω·m
Ans: A

562. The unit of magnetic flux density is
A) Tesla
B) Weber
C) Henry
D) Ampere-turn
Ans: A

563. Soft magnetic materials are preferred for
A) Transformer cores
B) Permanent magnets
C) Loudspeakers
D) Heating elements
Ans: A

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

565. Eddy current loss in transformer cores is minimized by
A) Laminating the core
B) Using soft iron
C) Increasing current
D) Using copper core
Ans: A

566. Hysteresis loss in magnetic materials depends on
A) Frequency and area of B-H loop
B) Magnetic field only
C) Current only
D) Voltage only
Ans: A

567. The Curie temperature of iron is
A) 770°C
B) 358°C
C) 1000°C
D) 500°C
Ans: A

568. The dielectric constant of mica is approximately
A) 6
B) 3
C) 10
D) 2
Ans: A

569. Piezoelectric materials are used in
A) Oscillators
B) Heaters
C) Transformers
D) Conductors
Ans: A

570. Quartz exhibits
A) Piezoelectric effect
B) Magnetic effect
C) Electrolytic effect
D) Thermionic effect
Ans: A

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571. The coercivity of a soft magnetic material is
A) Low
B) High
C) Infinite
D) Zero
Ans: A

572. The coercivity of a hard magnetic material is
A) High
B) Low
C) Zero
D) Medium
Ans: A

573. The energy stored per unit volume in a magnetic field is given by
A) ½ B·H
B) ½ μ H²
C) Both A and B
D) None
Ans: C

574. Which of the following is a ferroelectric material?
A) Barium titanate
B) Quartz
C) Mica
D) Silicon
Ans: A

575. Dielectric loss occurs due to
A) Molecular friction in the dielectric
B) Magnetic hysteresis
C) Electrical conduction
D) Temperature rise only
Ans: A

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

577. Resistivity of semiconductors decreases with
A) Increase in temperature
B) Decrease in temperature
C) Constant temperature
D) None
Ans: A

578. Diamagnetic materials have
A) Small negative susceptibility
B) Large positive susceptibility
C) High coercivity
D) Retentivity
Ans: A

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

580. Magnetic domains are
A) Regions of aligned atomic magnetic moments
B) Random magnetic spins
C) Insulating regions
D) Non-magnetic regions
Ans: A

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581. Retentivity is
A) Ability of a material to retain magnetism
B) Ability to resist demagnetization
C) Magnetic susceptibility
D) Magnetic flux density
Ans: A

582. Coercivity is
A) Ability to resist demagnetization
B) Ability to store energy
C) Permeability
D) Susceptibility
Ans: A

583. The hysteresis loop of a soft magnetic material is
A) Narrow
B) Wide
C) Infinite
D) Zero
Ans: A

584. Silicon steel is used for transformer cores because it has
A) Low hysteresis loss
B) High coercivity
C) High resistance
D) Low permeability
Ans: A

585. Electrical resistivity of metals
A) Increases with temperature
B) Decreases with temperature
C) Remains constant
D) Depends on magnetic field only
Ans: A

586. Electrical resistivity of semiconductors
A) Decreases with temperature
B) Increases with temperature
C) Remains constant
D) Infinite at room temperature
Ans: A

587. Electrical strain gauges work on
A) Variation of resistance with strain
B) Magnetic effect
C) Dielectric property
D) Piezoelectric effect
Ans: A

588. Electrical conductivity is the reciprocal of
A) Resistivity
B) Permeability
C) Permittivity
D) Coercivity
Ans: A

589. Thermal resistivity is reciprocal of
A) Thermal conductivity
B) Electrical conductivity
C) Specific heat
D) Resistivity
Ans: A

590. In n-type semiconductor, electrons are
A) Majority carriers
B) Minority carriers
C) Neutral
D) None
Ans: A

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591. In p-type semiconductor, holes are
A) Majority carriers
B) Minority carriers
C) Neutral
D) None
Ans: A

592. The electric displacement vector D =
A) εE
B) E/ε
C) ρE
D) μE
Ans: A

593. Dielectric materials are characterized by
A) Permittivity
B) Permeability
C) Conductivity
D) Resistivity only
Ans: A

594. The dielectric strength is measured in
A) kV/mm
B) A/m
C) Wb/m²
D) Ω·m
Ans: A

595. Electric dipole moment is measured in
A) C·m
B) V·m
C) A·m
D) Wb/m
Ans: A

596. A good magnetic material for a transformer has
A) High permeability and low hysteresis loss
B) High coercivity
C) High resistivity
D) None
Ans: A

597. Permanent magnets require
A) High coercivity
B) Low coercivity
C) Low retentivity
D) High permeability
Ans: A

598. Soft iron is preferred in electromagnets due to
A) Low coercivity
B) High coercivity
C) High resistivity
D) Low permeability
Ans: A

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

600. The Fermi level in p-type semiconductor is
A) Near valence band
B) Near conduction band
C) Mid-gap
D) At zero energy
Ans: A