Semiconductors and Superconductors

Q. What is shape of graph of resistivity of manganin vs temperature

Q. Find the moment of inertia of a rectangular bar magnet about an axis passing through its centre and parallel to its thickness. Mass of the magnet is 100 g, length is 12 cm, breadth is 3 cm and thickness is 2 cm.

Q. 56.The emissisivity of tungsten is approximately 0.35. A tungsten sphere 1 cm in radius is suspended within a large evacuated enclose whose walls are at 300k. What power input is required to maintain the sphere at a temperature of 3000k, if heat conduction along the support is neglected?

Q. Electric conduction in a semiconductor takes place due to 1)electrons only 2)holes only 3)both 4)none

Q. ${\mu }_e$ and ${\mu }_h$ are the electron and hole mobilities of a semiconducting crystal respectively. $E$ is the applied electric field. Then the current density $J$ for the intrinsic semiconductor is (Take $n_i$ the intrinsic concentration of the semiconductor)-

1. $\frac{n_{i}e({\mu }_e+{\mu }_h)}{E}$
2. $\frac{E}{n_{i}e({\mu }_e+{\mu }_h)}$
3. $n_{i}e({\mu }_e+{\mu }_h)E$
4. $n_{i}e({\mu }_e-{\mu }_h)E$