Materials and Components Questions

• Response of a rare-gas atom in a uniform electric field An atom of a rare gas is placed in a uniform electric field E. What happens to the nucleus, and how does this relate to atomic polarization?
• Imperfect dielectrics and equivalent circuit — assertion–reason Assertion (A): A capacitor with an imperfect (lossy) dielectric can be modeled as a capacitance in parallel with a resistance. Reason (R): For imperfect dielectrics, the dielectric constant is complex with real and imaginary parts (ε* = ε′ − jε″).
• Metallic bonding and electron sharing In a crystalline metal, how are the valence electrons shared among atoms according to the metallic-bonding model?
• Dielectric loss versus frequency In electrical insulation engineering, dielectric materials exhibit energy dissipation when stressed by an alternating electric field. Consider the statement: “The dielectric losses do not depend on frequency.” Determine whether this statement is true or false, and justify the correct understanding of how loss varies with frequency in real dielectrics used in capacitors, cables, and high-voltage equipment.
• Name the rule for splitting conductor resistivity into temperature-independent and temperature-dependent parts In solid-state physics and electrical engineering, the empirical rule that expresses total resistivity of a metal as the sum of a temperature-independent term (residual) and a temperature-dependent phonon term is called:
• Driven electron cloud (Lorentz model) under an alternating electric field If m is the electron mass in an atom's bound electron cloud, write the standard scalar equation of motion for the electron displacement x(t) when the dielectric is excited by a sinusoidal electric field E(t) = E0 cos(ω t). Include a linear restoring term and damping representative of collisions (classical Lorentz oscillator model).
• Definition check: Magnetization M of a material Consider the statement: “Magnetization of a material is the magnetic dipole moment per unit volume (m^3).” Decide whether this statement is true or false and interpret its engineering relevance for magnetic circuit calculations.
• Basic classification: What must a dielectric material be? In the context of electrostatics and AC insulation, a dielectric is a material that can be polarized but does not allow appreciable DC conduction. Which option best describes what a dielectric must be for practical purposes?
• Fleming's hand rules – identify what the left-hand rule gives In electromagnetism, Fleming's left hand rule is applied to determine which of the following directions in a motor or current-carrying conductor placed in a magnetic field?
• Inductor core choice at high frequencies For RF and high-frequency applications, which core type is preferred for inductors to minimize core losses and maintain high Q?
• Hole concept: motion of a vacant electronic state Consider the statement: “A vacant electronic state (a hole) moves in the same direction as a positive charge carrier would.” Determine whether this is true in semiconductor physics and briefly justify.
• Effect of inserting a dielectric slab on stored energy in a parallel-plate capacitor A parallel-plate capacitor is connected to a constant-voltage source. When a dielectric slab is fully inserted between the plates, the energy stored in the capacitor increases to five times its original value. What is the dielectric constant (relative permittivity) of the material?
• Van der Waals (molecular) crystals and electron shells Evaluate the statement: “In van der Waals crystals (e.g., rare-gas solids and many molecular crystals), there exists a high degree of stability of the outer electron shell.” Indicate whether it is true or false and explain in terms of bonding and electronic structure.
• Capacitor filled with dielectric after charging A vacuum parallel-plate capacitor is first charged and then isolated. The initial electric field between the plates is 2 × 10^4 V/m. If the space between the plates is subsequently filled completely with a dielectric material of relative permittivity εr = 10, what will be the new electric field inside the dielectric (assume the free charge on plates remains constant)?
• Fermi level occupancy at absolute zero If WF denotes the Fermi energy in a metal at T = 0 K, which statement correctly describes the occupation of energy levels at and around WF?
• Units of electric dipole moment in molecular physics Electric dipole moments for molecules are often reported in debye (D). Is it correct to say that electric dipole moment is expressed in the debye unit (noting that SI uses coulomb–metre)?
• Do all magnetic materials exhibit saturation? Consider diamagnetic, paramagnetic, ferromagnetic, ferrimagnetic, and antiferromagnetic classes. Is it correct to state that all magnetic materials show saturation behavior?
• Linearity of inductors and magnetic cores Which of the following inductors behaves most linearly with current over a wide range (i.e., exhibits negligible magnetic saturation and constant inductance)?
• Units for intrinsic dielectric strength In high-voltage engineering, the intrinsic dielectric strength (breakdown strength) of an insulating medium is quantified in which units?
• Spontaneous magnetization and ferromagnetism Is spontaneous magnetization (nonzero magnetization without an external field below a critical temperature) a defining characteristic of ferromagnetic materials?