151. The law that (where K is thermal conductivity, σ is electrical conductivity and T is absolute temperature) for all metals is equal to a universal constant is known as
152. In elemental dielectrics, the orientation and ionic polarization are absent.
153. In which of the following semiconductor are holes majority carriers
154. The equation D = ∈0∈r E refers only to isotropic materials.
155. When a ferromagnetic substance is magnetised there are small changes in dimensions. This phenomenon is called
156. 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.
157. An electron in a homogeneous magnetic field and having velocity perpendicular to the direction of field moves
158. Spontaneous polarization occurs in ferroelectric materials.
159. For a given value (n) of principle quantum number, the number of possible electronic states are
160. Electrical conductivity of metals expressed in ohm-1 m-1 is of the order of
161. In a metal the probability of a state 0.1 eV below Fermi level being occupied
162. 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.
163. A dielectric is subjected to alternating field. The dielectric losses are potential to
164. Semiconductors have a positive temperature coefficient of resistivity.
165. From a homogeneous and isotropic dielectric material of dielectric constant ∈r, a small volume element is taken out creating a cavity. The field can be kept homogeneous if Di. (i.e., electric flux density inside the cavity) and D0 (i.e., electric flux density outside the cavity) are such that
166. An electrolytic capacitor can be used for
167. Figure shows a composite capacitor. If CA, CB, CC are the capacitances of capacitors A, B, C, the overall capacitance C is
168. As regards ferromagnetic Curie temperature Qf and paramagnetic curie temperature θ
169. If there are no permanent dipoles in a dielectric material, the dielectric constant is independent of temperature.
170. Assertion (A): Magnetic susceptibility of copper is -0.5 x 10-5.Reason (R): Copper is diamagnetic material.
171. An electron shell corresponding to principal quantum number n can contain a maximum of
172. A sheet of bakelite is inserted between the plates of an air capacitor. The capacitance will
173. The spin angular momentum along a given direction is either or .
174. Lines of magnetic field cannot intersect.
175. 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.