Materials and Components Questions

• Rochelle salt is a ferroelectric material.
• Ferromagnetic materials
• The heat developed per m3 per second (W) in a conductor having a conductivity σ and a field E is
• The relationship of hysteresis loss to maximum flux density was first determined by
• A material which is lightly repelled by a magnetic field is known as
• The field pattern of a solenoid is similar to that of bar magnet.
• A 200 turn coil has a self inductance of 10 mH. If the number of turns is doubled, all other quantities remaining the same, the self inductance will be
• In a specimen of ferromagnetic material, as the flux density is increased from zero to 2.5 T, µr will
• The number of valence electrons in acceptor impurity are
• Ferrites have
• A permeable substance is one
• Which of the following is the poorest conductor of electricity?
• In a pure sample of silicon
• In intrinsic semiconductors, the number of free electrons is equal to the number of mobile holes.
• Assertion (A): In a parallel plate capacitor having area of plate 1 m2 and plate separation 1 m, the capacitance C and resistance R are given by C = ∈0∈'r and R = where ω is frequency, ∈r' and ∈r" are real and imaginary parts of dielectric constant. Reason (R): The imaginary part of electric constant is responsible for dielectric losses.
• 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.
• When subjected to alternating stresses, an insulating material is characterised by complex dielectric constant ∈'r - j∈"r . In such materials, the dielectric losses under alternating stress is proportional
• 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 tc are related as λ = vTc.
• Assertion (A): CO2 has no resultant dipole moment but CO has a dipole moment. Reason (R): The structure of CO2 is O = C = O.
• Paramagnetic materials have permanent magnetic dipoles but interaction between neighbouring dipoles is negligible.