Materials and Components Questions

• The class of insulation of impregnated paper is
• In body centred cubic structure, comers and centre of the cube are occupied by identical atoms.
• An iron specimen has µr = 1000 when B = 0.3 T. If B = 0.35 T, µr
• If v is the velocity of electron, tc is the average time between collisions, the mean free path λ = vtc.
• The colour code on a carbon resistor is red-red-black-silver. The value of resistor is
• The orientation polarization is directly proportional to temperature inversely proportional to temperature inversely proportional to square of permanent dipole moment directly proportional to square of permanent dipole moment. Which of the above are correct?
• To produce magnetic flux, mmf is necessary.
• In carbon resistor colour code, if the third band is of silver, it indicates
• 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.
• 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
• The temperature coefficient of a thermistor
• 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.
• As per Bohr's postulate, only those circular orbits are stable for which the angular momentum is equal to an integer times .
• Nichrome is used for
• 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
• Permeability is analogous to
• The circumference of an electron orbit is equal to integer times the wavelength of electron.
• At a temperature of about 1 K, aluminium is a
• For a multiplate capacitor having n plates, A as area of each plate, the capacitance is proportional to
• A material has N spins per m3. If Np are the dipoles per m3 parallel to field and Na are the dipoles per m3 anti-parallel to field, the magnetisation is