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You Are On Multi Choice Question Bank SET 1228

61401. Wood is a diamagnetic material.



61402. Curie Weiss law is .



61403. Consider the following materials NickelSilverOxygenAluminium The correct sequence in the order of decreasing permeability is





61404. The unit for mmf is





61405. A magnetic field exists around





61406. A conductor carries 10 A current in + x direction and is lying in a field having a flux density 0.2 T directed along + z direction. The magnitude of force per metre length and direction are





61407. The residual resistivity of a binary alloy at 0 K is





61408. The resistance of a photoconductor





61409. If the number of atoms per unit volume of a monoatomic gas changes, the dielectric constant still remains constant.



61410. The number of protons in a copper atom are





61411. When a material is in superconducting state and a magnetic field is applied





61412. For a diamagnetic material, μr = 1.



61413. We can know the arrangement of atom in a material by studying electron diffraction pattern.



61414. The elements which become superconducting at extremely low temperatures are





61415. Electrical contact materials used in switches, brushes, relay must possess





61416. If μp is permanent dipole moment and T is absolute temperature, the orientation polarization of polyatomic gases is




61417. The phenomenon of dielectric hysteresis occurs with





61418. The induced magnetic dipole moment is independent of the permanent magnetic dipole moment.



61419. The core of a solenoid is made of material of relative permeability μr. A small cavity area dA and length dl is cut in the core. If it is desired that flux density in the cavity should be equal to B0





61420. 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





61421. 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.





61422. As the atoms of rare gases become larger, electronic polarizability





61423. Ferrimagnetic materials have anti-parallel orientation of equal moments of permanent dipoles.



61424. Yettrium-iron garnet (Y2Fe5O12) is a soft magnetic material suitable for applications involving





61425. The mass of proton and electron are





61426. 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.



61427. In an intrinsic semiconductor, at a given temperature T





61428. The temperature at which some materials become superconductors is called





61429. In Fermi-Dirac statistics, the probability of electron occupation of an energy level equal to Fermi level is





61430. The quantum numbers associated with electron motion are designed as





61431. The carrier mobility in a semiconductor is 0.4 m2/Vs. Its diffusion constant at 300 K will be (in m2/s)





61432. Which of these has lowest dielectric strength?





61433. As per Curie-Weiss law, the magnetic susceptibility of a material varies as




61434. The amount of time between the creation and recombination of a free electron and hole is called





61435. A photoconductor is a





61436. Assertion (A): Both sodium and ferrous are ferromagnetic.Reason (R): Both sodium and ferrous have body centred cubic structure.





61437. For iron, the ferromagnetic Curie temperature is





61438. As regards dielectric constant εr





61439. 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





61440. In ferromagnetic materials, the orientation between neighbouring permanent dipoles is parallel.



61441. Resistivity of copper is lower than that of nickel. When a small percentage of copper is added to nickel, the resistivity





61442. Lines of magnetic field attract each other.



61443. The maximum temperature limit of class B insulation is





61444. Resistivity of metals consists of two parts, one part constant and the other temperature dependent.



61445. The number of valence electrons in germanium atom is





61446. Assertion (A): ∈0 has the dimensions of farad per meter.Reason (R): D = ∈0∈r E.





61447. When temperature is more than ferromagnetic curie temperature, the behaviour of a ferromagnetic material is similar to that of paramagnetic material.



61448. 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.



61449. The resistance of a superconductor is





61450. Dielectric constant, under the condition of alternating fields, is a complex quantity.



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