61101. For a photoconductor with equal electron and hole mobilities and perfect ohmic contacts at the ends, an increase in intensity of optical illumination results in
61102. A permeable substance is one
61103. 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
61104. The classes of solid dielectrics are
61105. 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
61106. A material which is lightly repelled by a magnetic field is known as
61107. Which of the following is the poorest conductor of electricity?
61108. The magnetic moment in units of Bohr magneton of a ferrous ion in any ferrite is
61109. The relationship of hysteresis loss to maximum flux density was first determined by
61110. In metals the thermal conductivity K and electrical conductivity σ are related as (K/σT) = L, L is known as
61111. 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.
61112. Dielectric constant of transformer oil is about
61113. 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.
61114. In carbon resistor colour code, the third band is red. It indicates
61115. Rochelle salt is a ferroelectric material.
61116. Paramagnetic materials have permanent magnetic dipoles but interaction between neighbouring dipoles is negligible.
61117. 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.
61118. 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.
61119. 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.
61120. A piece of iron is placed in a magnetic field
61121. 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.
61122. Ferromagnetic materials
61123. In a specimen of ferromagnetic material, as the flux density is increased from zero to 2.5 T, µr will
61124. 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.
61125. Assertion (A): Copper is a monoatomic solid.Reason (R): In a metal the valence electrons belong to all atoms.
61126. The heat developed per m3 per second (W) in a conductor having a conductivity σ and a field E is
61127. The number of valence electrons in acceptor impurity are
61128. 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
61129. At a very low temperature, a semiconductor
61130. The colour code on a carbon resistor is red-red-black-silver. The value of resistor is
61131. Some typical examples of macroscopic quantities are
61132. The temperature coefficient of a thermistor
61133. Assertion (A): Helium, Argon and Neon are gaseous at room temperature.Reason (R): The atoms in Helium, Argon and Neon are chemically extremely inactive.
61134. Resistivity of rubber is about
61135. An iron specimen has µr = 1000 when B = 0.3 T. If B = 0.35 T, µr
61136. Which solid dielectric has highest temperature limit?
61137. Permeability is analogous to
61138. The colour code on a carbon resistor is green-blue-yellow. The tolerance is
61139. The resistivity of intrinsic semiconductors, at room temperature, is of the order of
61140. 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.
61141. In terms of classical representation of electrons
61142. To produce magnetic flux, mmf is necessary.
61143. ‘Malta Vilasa Prahansa’ was written during the period of?
61144. The relaxation time of electrons in a metal is of the order of
61145. 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.
61146. The circumference of an electron orbit is equal to integer times the wavelength of electron.
61147. 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
61148. 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.
61149. The first president of Indian National Congress?
61150. 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