Sn (tin) is a metal, and Si (silicon) is a semiconductor. The key difference lies in the energy band gap between the valence band and the conduction band.
- In metals like Sn, the energy gap between the valence and conduction bands is negligible or practically zero, meaning electrons can move freely to the conduction band at room temperature, allowing Sn to conduct electricity easily.
- In semiconductors like Si, there is a small but non-zero energy gap (about 0.07 eV) that separates the valence band and conduction band. This small energy gap allows Si to conduct electricity under certain conditions (e.g., at higher temperatures or when doped with other materials).
Thus, the correct reason for Sn being a metal and Si being a semiconductor is the difference in their energy gaps, with Sn having no significant gap.
Extrinsic semiconductors are made by doping pure or intrinsic semiconductors with suitable impurity. There are two types of dopants used in doping, Si or Ge, and using them p-type and n-type semiconductors can be obtained. A p-n junction is the basic building block of many semiconductor devices. Two important processes occur during the formation of a p-n junction: diffusion and drift. When such a junction is formed, a ’depletion layer’ is created consisting of immobile ion-cores. This is responsible for a junction potential barrier. The width of a depletion layer and the height of potential barrier changes when a junction is forward-biased or reverse-biased. A semiconductor diode is basically a p-n junction with metallic contacts provided at the ends for application of an external voltage. Using diodes, alternating voltages can be rectified.
A solid cylinder of mass 2 kg and radius 0.2 m is rotating about its own axis without friction with angular velocity 5 rad/s. A particle of mass 1 kg moving with a velocity of 5 m/s strikes the cylinder and sticks to it as shown in figure.
The angular velocity of the system after the particle sticks to it will be: