Materials and Components Questions

• The units for ∈r are
• A piece of copper and another piece of Germanium are cooled from 30°C to 80 K. The resistance of
• Magnetic hysteresis phenomenon is explained by
• The relative permeability of a ferromagnetic material is
• Some ceramic materials become superconducting
• As the temperature of semiconductor is increased
• For an insulating material, dielectric strength and dielectric losses should be
• Macroscopic quantities of a given material
• Assertion (A): Ferrites are very useful at very high frequencies. Reason (R): Ferrites have high permeability and high resistivity.
• If v is velocity of electron, ε0 is absolute permittivity, m is mass of electron, e is charge on electron and r is the radius of orbit of electron in hydrogen atom, the stability of orbit requires the following equation to be satisfied
• Assertion (A): For a dielectric, P = ∈0(∈r - 1) E. Reason (R): Dipole moment per unit volume is called polarization of dielectric.
• Eddy current loss is
• Consider the following statement: In case of a superconductor B = 0 μr is high diamagnetism is high transition temperature varies with isotopic mass. Of the above statements
• Assertion (A): In liquids and glassy substances, dielectric losses occur. Reason (R): The orientation polarization in many substances is frequency dependent.
• The dipole moment per unit volume P as a function of E for an insulator is
• The current flow in a semiconductor is due to
• Assertion (A): In ionic dielectrics, P = Pe + Pi. Reason (R): In ionic crystals, permanent electric dipole moment is zero.
• A copper atom is neutral. Its core has a net charge of
• A parallel plate capacitor has area of plate A and plate separation d. Its capacitance is C. A metallic plate P of area A and negligible thickness is added as shown in Figure. The new value of capacitance is
• Assertion (A): In an intrinsic semiconductor J = (μn x μp)eni. Reason (R): Intrinsic charge concentration ni at temperature T is given by ni2 = A0 T3 e-EG0/kT.