List of top Physics Questions on Classification Of Metals, Conductors And Semiconductors asked in CBSE CLASS XII

Assertion (A): In a semiconductor, the electrons in the conduction band have lesser energy than those in the valence band.
Reason (R): Donor energy level is just above the valence band in a semiconductor.
On the basis of energy band diagrams, distinguish between (i) an insulator, (ii) a semiconductor, and (iii) a conductor.
Draw the circuit diagrams for obtaining the V-I characteristics of a p-n junction diode. Explain briefly the salient features of the V-I characteristics in (i) forward biasing, and (ii) reverse biasing.
Suppose a pure Si crystal has \(5 \times 10^{28}\) atoms m\(^{-3}\). It is doped by 1 ppm concentration of boron. Calculate the concentration of holes and electrons, given that \(n_i = 1.5 \times 10^{16}\) m\(^{-3}\). Is the doped crystal n-type or p-type?
Silicon is doped with a pentavalent element. The energy required to set the additional electron free is about:
An air-filled parallel plate capacitor (d = 1mm, C = 20pF) is charged to 4.0µC. Find work done to increase plate separation to 5mm (constant charge).
How does conductivity of an intrinsic semiconductor vary with temperature? Show in a plot.