Materials and Components Questions

• The iron core of a coil is removed so that it becomes an air cored coil. Its inductance will
• In a metal the probability of a state 0.1 eV below Fermi level being occupied
• When a ferromagnetic substance is magnetised there are small changes in dimensions. This phenomenon is called
• Electrical conductivity of metals expressed in ohm-1 m-1 is of the order of
• In a polyatomic gas, the types of polarization which exist together are
• In elemental dielectrics, the orientation and ionic polarization are absent.
• An electron in a homogeneous magnetic field and having velocity perpendicular to the direction of field moves
• An homogeneous dielectric material is subjected to an electric field E. If a small cavity is made inside the material, the electric field intensity inside and outside the cavity are different.
• A particle of charge Q coulombs is bound elastically to an equilibrium position with a force constant of f newton per metre. The polarizability of the system is
• In an hydrogen atom, an electron moves in the field of a proton. The stability of orbit requires equilibrium between coulomb's force and centrifugal force.
• An electron shell corresponding to principal quantum number n can contain a maximum of
• Assertion (A): Dielectric losses are proportional to tan δ. Reason (R): tan δ = where ∈r' and ∈r" denote the real and imaginary parts of ∈r.
• Spontaneous polarization occurs in ferroelectric materials.
• For a core having a relative permeability μr, magnetic dipole moment per unit volume M and field strength H, the flux density B is
• Figure shows a composite capacitor. If CA, CB, CC are the capacitances of capacitors A, B, C, the overall capacitance C is
• Assertion (A): In some materials, ∈r is independent of temperature while in others, ∈r depends on temperature. Reason (R): If permanent dipoles are absent, ∈r varies with temperature.
• The direction of force an a conductor carrying current and lying in a magnetic field can be found by using
• The real part of complex dielectric constant and tanδ for a dielectric are 2.1 and 5 x 10-4 at 100 Hz respectively. The imaginary part of dielectric constant at 100 Hz is
• A single layer air cored coil has n turns and inductance L. If a new coil is formed by having 2n turns while keeping the coil length and diameter the same, the new inductance is
• In anti-ferromagnetic materials, the graph of susceptibility versus temperature shows a sharp maximum at a certain temperature. This temperature is known as