Materials and Components Questions

• Conductivity due to holes in a p-type semiconductor In a p-type semiconductor, what is the expression for the contribution of holes to electrical conductivity? (e is the elementary charge, μp is hole mobility, p is hole concentration.)
• Assertion–Reason on majority carriers in p-type semiconductors Assertion (A): Holes are the majority carriers in a p-type semiconductor. Reason (R): In a p-type semiconductor, electrons produced by thermal agitation recombine with holes.
• Atoms per conventional cubic cell in the diamond structure Silicon and germanium crystallize in the diamond structure. How many atoms are contained in a conventional cubic cell of volume a^3 (where a is the cubic lattice parameter)?
• Specific resistivity (electrical resistivity) of silver at standard conditions What is the approximate specific resistance (resistivity) of silver, expressed in Ω·m (ohm-metre), under normal room-temperature conditions?
• Force between two long, parallel transmission-line conductors carrying equal and opposite currents Two conductors of a transmission line carry equal current I in opposite directions. How does the magnetic force on each conductor vary with current?
• Crystallography concept check A characteristic property of a crystal is the periodicity of its atomic structure (long-range order). Is this statement correct?
• Electronic polarizability vs. atomic size; constitutive relation for dilute gases Assertion (A): Electronic polarizability increases as atoms become larger. Reason (R): For rare gases, the relation ε0 (εr − 1) E = N αe E holds, where N is the number of atoms per m^3 and αe is the electronic polarizability.
• Classification of solids by bonding type On the basis of the dominant chemical bonding, solids may be classified into which groups?
• Definition check: Piezoelectricity (converse effect) “Piezoelectricity means a slight change in the dimensions of a specimen when an electric field is applied.” Evaluate this statement.
• Order of magnitude of Debye temperature for metals What is a typical order-of-magnitude value of the Debye temperature θD for common metals?
• Leakage in real capacitors – equivalent circuit representation A practical (leaky) capacitor is often modeled by an ideal capacitance C in parallel with a finite resistance R representing leakage. Is this representation correct?
• Magnetic field direction around a long, straight current-carrying wire A long, straight wire carries current I. What is the direction of the magnetic field intensity H at a point located a distance r from the wire?
• Fundamentals of piezoelectricity in materials Materials that become electrically polarized when a mechanical stress (compression, tension, or shear) is applied are called piezoelectric. Confirm whether this definition is correct.
• Electron transport in metals: relation between relaxation time and mean free time If τ is the relaxation time and τc is the average time between successive electron–scattering collisions in an isotropic metal, which relation holds under the Drude model assumptions?
• Low-temperature resistivity of a perfect metal crystal Assertion (A): The resistivity of a perfect single crystal of a metal tends to zero as temperature T approaches 0 K. Reason (R): Electron scattering arises from deviations from perfect lattice periodicity (e.g., phonons and defects), which vanish in an ideal, defect-free crystal at 0 K.
• Semiconductor fundamentals: name the process when a free electron meets a hole What is the term for the event in which a conduction-band electron combines with a valence-band hole, eliminating both charge carriers?
• Dielectric loss and complex polarizability When a dielectric is subjected to an alternating electric field, the material absorbs energy from the field. This loss is represented by the imaginary part of the complex polarizability. Decide if this statement is correct.
• Effect of number density on dielectric constant of a monoatomic gas Consider a monoatomic gas (e.g., a rare gas). If the number of atoms per unit volume changes, does its relative dielectric constant remain unchanged?
• Residual resistivity of binary alloys at absolute zero At T = 0 K, the residual resistivity of a binary alloy primarily is:
• Properties of the relative dielectric constant (relative permittivity) Which statements about the relative dielectric constant εr are correct? It is dimensionless. It equals 1 for vacuum. It equals 1 for all substances.