Materials and Components Questions

• Why RF inductors and capacitors are silver-plated High-frequency inductors and some capacitor plates are often silver-plated. What is the primary purpose of this surface treatment?
• Nichrome — typical engineering application Nichrome (a nickel–chromium resistance alloy) is widely used in which of the following applications?
• Metals as thermal conductors — assessing the explanation Assertion (A): Metals are better heat conductors than electrical insulators. Reason (R): If dT/dx is the temperature gradient, Q is heat-flux density, and K is thermal conductivity, then Q = − K (dT/dx).
• Temperature coefficient of resistivity for semiconductors Consider intrinsic or lightly doped semiconductors around room temperature. Do semiconductors have a positive temperature coefficient of resistivity?
• Use of electrolytic capacitors — polarity and waveform suitability An electrolytic capacitor (single polarized unit) is suitable for use with which type of applied voltage?
• Counting electronic states in a principal shell For a given principal quantum number n, how many one-electron states (including all allowed orbital and spin states in that shell) are possible?
• Capacitance change with dielectric insertion A sheet of Bakelite (a solid dielectric) is inserted fully between the parallel plates of an air capacitor without changing plate area or separation. What happens to the capacitance?
• Magnetic domains in virgin iron State whether the following statement is true or false: “In a virgin (demagnetized) specimen of iron, the direction of spontaneous magnetization varies from domain to domain.”
• Orientation polarization in gases and temperature dependence State whether the following statement is true or false: “For a polyatomic gas composed of polar molecules, the orientation (dipolar) polarization is inversely proportional to absolute temperature.”
• Ion charge after removing a valence electron — copper atom case If the single valence electron is removed from a neutral copper atom, what is the net charge of the remaining ion (in units of the elementary charge)?
• Assertion–Reason: magnetic susceptibility of copper and diamagnetism Assertion (A): The magnetic susceptibility of copper is approximately −0.5 × 10^−5. Reason (R): Copper is a diamagnetic material.
• Temperature effect on dielectric constant without permanent dipoles State whether the following is true or false: “If a dielectric material has no permanent dipoles, then its dielectric constant is independent of temperature (over ordinary ranges).”
• Assertion–Reason on hardness of diamond and carborundum (silicon carbide) Assertion (A): Diamond and carborundum (silicon carbide) are both very hard materials. Reason (R): The valence band can be extremely strong.
• Magnetic field lines — can they intersect? State whether the following is true or false: “Lines of magnetic field cannot intersect one another at a point.”
• Constitutive relation D = ε0 εr E — scope of validity State whether the following is true or false: “The scalar relation D = ε0 εr E applies only to isotropic, linear dielectrics. For anisotropic media, ε must be treated as a tensor.”
• Dielectrics under AC field – dependence of dielectric loss on complex permittivity A dielectric material is subjected to an alternating electric field. The complex relative permittivity is written as ε_r = ε' – j ε'. The dielectric power loss in the medium is primarily proportional to which component(s) of the dielectric constant?
• Atomic structure of silicon – count of tightly bound (core) electrons In a neutral silicon atom (Z = 14), how many electrons are tightly bound in inner shells (i.e., non-valence/core electrons), as opposed to the 4 valence electrons used in bonding?
• Units – Debye as a measure of electric dipole moment Electric dipole moment is often reported in Debye (D). Choose the correct SI-equivalent for 1 Debye.
• Orbital magnetic moment of an electron in circular motion An electron (charge −e in sign, magnitude e) revolves in a circular orbit of radius R around a proton with constant angular velocity ω. What is the magnitude of its orbital magnetic dipole moment?
• Dielectric classification – definition of elemental dielectrics Elemental dielectrics are dielectrics composed of only one kind of atom (for example, noble gases like helium, neon, argon). Is this statement correct?