Materials and Components Questions

• Wire gauge units – definition of a circular mil In electrical engineering practice, a “circular mil” is defined as the area of a circular wire having which of the following geometric properties?
• Fundamental constants – value of one Bohr magneton Select the correct value and SI unit for one Bohr magneton (μ_B).
• Surge protection components – lightning arrester material choice Which of the following components is commonly used inside modern lightning arresters/surge protectors to clamp overvoltage transients?
• Hydrogen-like atom – ground-state binding energy In its lowest (ground) state, the electron bound to a proton (hydrogen atom) has a binding/ionization energy equal to which of the following?
• Curie temperatures – relation between ferromagnetic Curie temperature (Q_f) and paramagnetic Curie temperature (θ) Considering the Curie–Weiss behavior of real ferromagnets, what is the most appropriate general statement about the relationship between the ferromagnetic Curie temperature Q_f (often denoted T_c) and the paramagnetic Curie temperature θ appearing in χ = C / (T − θ)?
• Internal (Molecular) Field in Ferromagnets In a ferromagnetic material, the magnetic dipole at a lattice site does not experience only the externally applied field H. Which description best represents the internal field sensed by a magnetic dipole inside a ferromagnet under magnetization?
• Majority Carriers in Semiconductors In which type of semiconductor are holes the majority charge carriers under thermal equilibrium?
• Thermal–Electrical Conductivity Link in Metals The empirical law stating that K / (σ * T) is approximately a universal constant for metals (where K is thermal conductivity, σ is electrical conductivity, and T is absolute temperature) is known as:
• What Determines Chemical Properties of Atoms? Consider the statement: “The chemical properties of atoms are determined by all the electrons and their complete configuration.” Is this statement accurate?
• Thermal Energy Scale at Room Temperature If k is Boltzmann’s constant and T is absolute temperature, what is the approximate value of kT (in electronvolts) at room temperature (≈ 300 K)?
• Cavity in a Dielectric – Condition for Uniform Field From a homogeneous, isotropic dielectric of relative permittivity εr, a small volume element is removed to create a cavity. To keep the electric field homogeneous across the cavity boundary, which relation between D_i (electric flux density inside the cavity) and D_0 (electric flux density in the surrounding dielectric) must hold?
• Metal Resistivity at Absolute Zero (Ideal Crystal) At T = 0 K, what is the electrical resistivity of a perfect single-crystal metal (no impurities, no defects)?
• Effect of Removing an Iron Core from a Coil An iron-cored inductive coil is converted into an air-cored coil by removing the iron core (geometry unchanged). How does its inductance change?
• Fermi–Dirac Occupancy Near the Fermi Level In a metal at ordinary temperatures, how does the probability of occupancy of a state 0.1 eV below the Fermi level compare with that of a state 0.1 eV above the Fermi level?
• Name of the Phenomenon: Dimensional Change on Magnetization When a ferromagnetic specimen is magnetized, very small changes in its dimensions are observed. What is this phenomenon called in materials science and magnetics?
• Metals – order of magnitude of electrical conductivity (units: Ω⁻¹·m⁻¹) What is the typical order of magnitude for the electrical conductivity of common metals (e.g., copper, aluminum) expressed in Ω⁻¹·m⁻¹ at room temperature?
• Dielectric polarization in polyatomic gases In a polyatomic gas (molecules with more than one atom), which types of polarization can simultaneously exist under an applied electric field?
• Elemental dielectrics – absence of orientational and ionic polarization Consider elemental dielectrics (e.g., noble gases or elemental solids). The statement “orientational polarization and ionic polarization are absent” is:
• Motion of an electron in a uniform magnetic field An electron enters a homogeneous magnetic field with its velocity perpendicular to the field direction. What path does it follow (neglecting electric fields and radiation)?
• Field in a cavity inside a homogeneous dielectric under uniform external field A small cavity (void) is created inside an otherwise homogeneous, isotropic dielectric subjected to a uniform electric field E. Will the electric field intensity inside the cavity equal the field in the surrounding dielectric?