74301. The magnetic moment in units of Bohr magneton of a ferrous ion in any ferrite is
74302. The relationship of hysteresis loss to maximum flux density was first determined by
74303. In metals the thermal conductivity K and electrical conductivity σ are related as (K/σT) = L, L is known as
74304. Assertion (A): If WF is Fermi energy, v is velocity of electron and m is mass of electron, then .Reason (R): Conductivity of a metal depends on temperature and impurity concentration.
74305. Dielectric constant of transformer oil is about
74306. Assertion (A): When an electron is revolving in its orbit and magnetic field is also present, the angular frequency of electron will be affected by the magnetic field.Reason (R): In the case of electron revolving in its orbit in the presence of magnetic field, the orbital magnetic dipole moment is not affected by the presence of magnetic field.
74307. In carbon resistor colour code, the third band is red. It indicates
74308. Rochelle salt is a ferroelectric material.
74309. Paramagnetic materials have permanent magnetic dipoles but interaction between neighbouring dipoles is negligible.
74310. Assertion (A): If difference between static and optical dielectric constant is high, the mechanical compressiblity of that material is also high.Reason (R): For soft ions, ionic polarization per unit field is higher than that of hard ions.
74311. Assertion (A): In Figure, the intercept of the line on y-axis is equal to N (a e + a i), where N is number of atoms/m3, a e is electronic polarizability and a i is ionic polarizability.Reason (R): a e and a i are independent of temperature.
74312. Assertion (A): The optical dielectric constant (i.e., εr at optical frequencies)of ionic dielectrics is less than static dielectric constant. Reason (R): At optical frequencies, Pi = 0.
74313. A piece of iron is placed in a magnetic field
74314. Assertion (A): Magnetism can be explained by the theory of magnetic domains.Reason (R): The existence of magnetic domains is evident from the Bitter powder patterns.
74315. Ferromagnetic materials
74316. In a specimen of ferromagnetic material, as the flux density is increased from zero to 2.5 T, µr will
74317. Assertion (A): Relaxation time and mean time between collisions are equal when scattering is isotropic.Reason (R): Mean free path of an electron λ, velocity of electron v and mean time between collisions t c are related as λ = vTc.
74318. Assertion (A): Copper is a monoatomic solid.Reason (R): In a metal the valence electrons belong to all atoms.
74319. The heat developed per m3 per second (W) in a conductor having a conductivity σ and a field E is
74320. The number of valence electrons in acceptor impurity are
74321. If q is charge on an electron, R is radius of electron orbit and ω is angular velocity of electron rotation, the magnetic dipole moment of electron in orbit is
74322. At a very low temperature, a semiconductor
74323. The colour code on a carbon resistor is red-red-black-silver. The value of resistor is
74324. Some typical examples of macroscopic quantities are
74325. The temperature coefficient of a thermistor
74326. Assertion (A): Helium, Argon and Neon are gaseous at room temperature.Reason (R): The atoms in Helium, Argon and Neon are chemically extremely inactive.
74327. Resistivity of rubber is about
74328. An iron specimen has µr = 1000 when B = 0.3 T. If B = 0.35 T, µr
74329. Which solid dielectric has highest temperature limit?
74330. Permeability is analogous to
74331. The colour code on a carbon resistor is green-blue-yellow. The tolerance is
74332. The resistivity of intrinsic semiconductors, at room temperature, is of the order of
74333. Assertion (A): Ferromagnetic materials possess ferromagnetic properties only when temperature is less than paramagnetic curie temperature.Reason (R): For a ferromagnetic material for T > θf.
74334. In terms of classical representation of electrons
74335. To produce magnetic flux, mmf is necessary.
74336. The relaxation time of electrons in a metal is of the order of
74337. Assertion (A): For elemental dielectrics, P = Na eEi where N is number of atoms/m3, P is polarization, a e is electronic polarization and Ei is internal electric field.Reason (R): In elemental dielectrics there are no permanent dipoles or ions.
74338. The circumference of an electron orbit is equal to integer times the wavelength of electron.
74339. In a specimen of silicon steel, a field strength of 200 A/m causes a flux density of 0.5 T. In a specimen of cast iron, the same H would cause B to be
74340. In a rare gas, the molecules of some atoms have an excess positive or negative charge. The electric field tends to shift positive ions relative to negative ions. This is known as ionic polarization.
74341. A liquid has N permanent dipoles μp per unit volume and has been subjected to dc field for a long time such that orientation polarization is P0. At t = 0, the field is suddenly removed, then polarization
74342. Assertion (A): Orbital magnetic moment of an electron in an atom is of the order of 1 Bohr magneton.Reason (R): 1 Bohr magneton = 9.27 x 10-24 A/m2.
74343. As per Bohr's postulate, only those circular orbits are stable for which the angular momentum is equal to an integer times .
74344. Inductors used at V.H.F. are made using
74345. If a capacitor C having selectivity factor Q is scaled down in all its dimensions by a factor K without any altering the dielectric material, the new capacitor will have capacitance and selectivity as
74346. The hysteresis loss is
74347. Assertion (A): For a magnetic material M = (μr - 1) H, where M is magnetic dipole moment/m3, H is field intensity A/m and μr is relative permeability.Reason (R): μr can have any value from 0 to hundreds of thousands.
74348. As regards ∈0 and ∈r (absolute and relative permittivity)
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