০০। ∈0 has no other physical meaning than that of a fundamental conversion factor.
ক) True
খ) False
০১। ∈r is determined by the atomic structure of the dielectric.
ক) True
খ) False
০২। 1 Bohr magneton = .
ক) True
খ) False
০৩। 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
ক) 2.5 mH
খ) 5 mH
গ) 20 mH
ঘ) 40 mH
০৪। A capacitor can be represented by a capacitance and resistance in parallel. For a good capacitor, this parallel resistance should be
ক) negligible
খ) low
গ) high
ঘ) very high
০৫। A characteristic property of crystal is its periodicity of structure.
ক) True
খ) False
০৬। A circular sphere mile is the area of cross-section of a wire
ক) having a diameter equal to 1 miles
খ) having a radius equal to 1 miles
গ) having a circumference equal to 1 miles
ঘ) none of the above
০৭। 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
ক) 2 N, + y direction
খ) 2 N, - y direction
গ) 0.02 N, + y direction
ঘ) 0.02 N, - y direction
০৮। A copper atom is neutral. Its core has a net charge of
ক) 0
খ) + 1
গ) - 1
ঘ) + 2
০৯। 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
ক) 1.6 x 10-8 Ω-m
খ) 2 x 10-8 Ω-m
গ) 3 x 10-8 Ω-m
ঘ) 6 x 10-8 Ω-m
১০। A dielectric is subjected to alternating field. The dielectric losses are potential to
ক) real part of dielectric constant
খ) imaginary part of dielectric constant
গ) both real and imaginary parts of dielectric constant
ঘ) either real or imaginary part of dielectric constant
১১। A dielectric material must be
ক) insulator
খ) good conductor
গ) resistor
ঘ) semiconductor
১২। A dielectric of relative permittivity ∈r is subjected to a homogeneous electric field E. The dipole moment P per unit volume is given by
ক) P = constant
খ) P = ∈0 E
গ) P = ∈0(∈r - 1) E
ঘ) P = ∈r E
১৩। A good dielectric should have
ক) low losses
খ) good heat conductivity
গ) high intrinsic strength
ঘ) all of the above
১৪। A leakage capacitor can be represented by a capacitance C and resistance R in parallel C.
ক) True
খ) False
১৫। A leaky dielectric has ∈r = ∈r' - j∈r". If a field E is applied, the current component in phase with E is proportional to ∈r".
ক) True
খ) False
১৬। 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
ক) will remain constant at P0
খ) will become zero at t = 0
গ) will delay to zero with a time constant
ঘ) either b or c
১৭। A magnet does not attract
ক) nickel
খ) iron
গ) copper
ঘ) iron and copper
১৮। A magnetic field exists around
ক) moving charges
খ) static charges
গ) iron
ঘ) copper
১৯। 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
.