Materials and Components Questions

• Automobile ignition systems use the principle of
• The materials having low retentivity are suitable for making
• The number of valence electrons in germanium atom is
• The carrier mobility in a semiconductor is 0.4 m2/Vs. Its diffusion constant at 300 K will be (in m2/s)
• Lines of magnetic field attract each other.
• If temperature is increased, the temperature coefficient of a metal
• In an homogeneous dielectric subjected to an electric field E, the dipole moment per unit volume is ∈0(∈r - 1) E.
• The temperature at which some materials become superconductors is called
• A parallel plate capacitor having C = 200 x 10-12 F has loss dielectric having tan δ = 4 x 10-4. At an ac voltage of f = 106 Hz and peak value 2 V, the dielectric losses are
• When temperature is more than ferromagnetic curie temperature, the behaviour of a ferromagnetic material is similar to that of paramagnetic material.
• The quantum numbers associated with electron motion are designed as
• Which of these has lowest dielectric strength?
• Transformer oil is
• Resistivity of copper is lower than that of nickel. When a small percentage of copper is added to nickel, the resistivity
• For a superconductor, magnetisation M in a field H is
• As per Curie-Weiss law, the magnetic susceptibility of a material varies as
• The application of magnetic field to superconducting material
• The resistance of a superconductor is
• In Fermi-Dirac statistics, the probability of electron occupation of an energy level equal to Fermi level is
• If ∈r = ∈r' - j∈r" tan δ = .