Materials and Components Questions

• When the atom of rare gas is placed in an electric field the nucleus shifts from the centre of electron cloud by an amount x. If the radius of electron cloud is R, then
• The units for electric dipole moment are
• For a superconductor, the relative permeability is
• Assertion (A): Copper is a good conductor of electricity. Reason (R): Copper has a face centred cubic lattice.
• The wavelength of light emitted by GaAs laser is 8670 x 10-10 m. If h = 6.626 x 10-34 Js, velocity of light = 3 x 108 m/s and eV = 1.602 x 10-19 J, the energy gap in GaAs is
• Assertion (A): Relative permittivity is determined by the atomic structure of the material. Reason (R): Absolute permittivity is determined by the atomic structure of the material.
• The core of an atom consists of
• Diamagnetic materials do not have permanent magnetic dipoles.
• Assertion (A): Rochelle salt and Barium titanate are both ferroelectric. Reason (R): Ferroelectric materials exhibit hysteresis effect.
• If a metal specimen has n valence electrons per m3 each having charge e and mass m and t is the relaxations time, the conductivity is
• Assertion (A): Intrinsic resistivity of silicon is lower than that of germanium. Reason (R): Magnitude of free electron concentration in germanium is more than that of silicon.
• In a conductor the current flow is due to
• Assertion (A): The equation D = ∈0∈rE is applicable only to isotropic materials. Reason (R): In polycrystalline materials, the directional effects are absent.
• A dielectric of relative permittivity ∈r is subjected to a homogeneous electric field E. The dipole moment P per unit volume is given by
• As per Matthiessen's rule, the total resistivity r of a conductor can be written as r = ri + aT, where ri and a are constants and T is absolute temperature. At very low temperatures
• Consider the following statements An iron cored choke is non linear and passive device. A carbon resistor kept in sunlight is a time invariant and passive device. A dry cell is a time varying and active device. An air capacitor is time invariant and passive device. Of these statements
• 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