127. The electric dipole moment of a neutral system of point charges Q1, Q2.... is Qiri . The charges Qi
128. The class of insulation of impregnated paper is
129. Assertion (A): The resistance of a copper specimen changes by about 22% when temperature is increased from room temperature to 700°C.Reason (R): The physical properties of a material are determined mostly by the extent of impurities.
130. Assertion (A): For most metals, Fermi energy EF is less than 10 eV.Reason (R): Fermi level of a metal is given by EF = 3.64 x 10-19 (n)2/3 where n is number of free electrons/m3 of metal.
131. The capacitance of an insulated conducting sphere of radius R in vacuum is
132. The transition of electron from energy level W1 to W2 is associated with emission or absorption of electro magnetic radiation of frequency f such that
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134. Even at room temperature, an intrinsic semiconductor has some holes. These holes are due to
135. In carbon resistor colour code, if the third band is of silver, it indicates
136. In a metal, the drift velocity of electrons in the presence of a electric field E is
137. At a temperature of about 1 K, aluminium is a
138. The first privatised river in India is?
139. If v is the velocity of electron, t c is the average time between collisions, the mean free path λ = vt c.
140. Assertion (A): An electron having charge - e and mass m and lying in an electric field E is subjected to an acceleration - (e/m) E.Reason (R): If there are n electrons/m3 moving with velocity vx and each electron has a charge - e, the current density J = - n evx.
141. When a pentavalent impurity is added, the semiconductor becomes
142. In body centred cubic structure, comers and centre of the cube are occupied by identical atoms.
143. For a multiplate capacitor having n plates, A as area of each plate, the capacitance is proportional to
144. The orientation polarization is directly proportional to temperatureinversely proportional to temperatureinversely proportional to square of permanent dipole momentdirectly proportional to square of permanent dipole moment. Which of the above are correct?
145. Assertion (A): Diamond and carborudum are both very hard materials.Reason (R): Valence band can be extremely strong.
146. The chemical properties of atoms are determined by all the electrons and their configuration.
147. If k is Boltzmann's constant and T is absolute temp, then at room temp.
148. If the valence electron is separated from a copper atom, the remaining part of atom has a net charge of
149. The dielectrics having only one kind of atoms are known as elemental dielectrics.
150. For a core having a relative permeability μr, magnetic dipole moment per unit volume M and field strength H, the flux density B is