74701. A copper specimen has resistivity equal to 1.8 x 10-8 ohm-m at room temperature. At a temperature of 700 K, the resistivity is likely to be
74702. Assertion (A): Dielectric constant is independent of temperature unless the temperature is extremely high.Reason (R): For normal temperatures the number of atoms per unit volume is constant.
74703. As the atoms of rare gases become larger, electronic polarizability
74704. Ferrimagnetic materials have anti-parallel orientation of equal moments of permanent dipoles.
74705. Yettrium-iron garnet (Y2Fe5O12) is a soft magnetic material suitable for applications involving
74706. The mass of proton and electron are
74707. A rare gas having N atoms/m3 is subjected to an electric field E. The electric dipole moment per unit volume is proportional to N and E.
74708. In an intrinsic semiconductor, at a given temperature T
74709. The temperature at which some materials become superconductors is called
74710. In Fermi-Dirac statistics, the probability of electron occupation of an energy level equal to Fermi level is
74711. The quantum numbers associated with electron motion are designed as
74712. The carrier mobility in a semiconductor is 0.4 m2/Vs. Its diffusion constant at 300 K will be (in m2/s)
74713. Which of these has lowest dielectric strength?
74714. As per Curie-Weiss law, the magnetic susceptibility of a material varies as
74715. The amount of time between the creation and recombination of a free electron and hole is called
74716. A photoconductor is a
74717. Assertion (A): Both sodium and ferrous are ferromagnetic.Reason (R): Both sodium and ferrous have body centred cubic structure.
74718. For iron, the ferromagnetic Curie temperature is
74719. As regards dielectric constant εr
74720. 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
74721. In ferromagnetic materials, the orientation between neighbouring permanent dipoles is parallel.
74722. Resistivity of copper is lower than that of nickel. When a small percentage of copper is added to nickel, the resistivity
74723. Lines of magnetic field attract each other.
74724. The maximum temperature limit of class B insulation is
74725. Resistivity of metals consists of two parts, one part constant and the other temperature dependent.
74726. The number of valence electrons in germanium atom is
74727. Assertion (A): ∈0 has the dimensions of farad per meter.Reason (R): D = ∈0∈r E.
74728. When temperature is more than ferromagnetic curie temperature, the behaviour of a ferromagnetic material is similar to that of paramagnetic material.
74729. If ω0 is the angular frequency of rotation of electron in the absence of magnetic field, the angular frequency ω, when a magnetic field B is acting is ω ≅ ω0 + (e/2m)B.
74730. The resistance of a superconductor is
74731. Dielectric constant, under the condition of alternating fields, is a complex quantity.
74732. In an homogeneous dielectric subjected to an electric field E, the dipole moment per unit volume is ∈0(∈r - 1) E.
74733. For a superconductor, magnetisation M in a field H is
74734. The probability of recombination of electrons and holes in a semiconductor is proportional to
74735. Assertion (A): The regular or irregular stacking of atoms has importanteffect on properties of materials.Reason (R): The arrangement of atoms in a given material can be studied using X-rays.
74736. If temperature is increased, the temperature coefficient of a metal
74737. The application of magnetic field to superconducting material
74738. Automobile ignition systems use the principle of
74739. In a valence crystal, the valence electrons
74740. Transformer oil is
74741. Assertion (A): Drift velocity of electrons is proportional to the applied electric field E.Reason (R): The average drift velocity per unit field is called mobility.
74742. The materials having low retentivity are suitable for making
74743. If ∈r = ∈r' - j∈r" tan δ = .
74744. Assertion (A): Electron concentration n, hole concentration p and charge concentration ni are related by ni2 = np.Reason (R): p type semiconductor is obtained by adding trivalent impurity to intrinsic semiconductor.
74745. Diamond is a paramagnetic material.
74746. Which capacitor-store higher amount of energy?
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