\(\mathrm{C}\), \(\mathrm{Si}\), and \(\mathrm{Ge}\) have the same lattice structure. Why is the \(\mathrm{C}\) insulator?

Suppose a pure Si crystal has \(5\times10^{28}~\text{atoms m}^{-3}\). It is doped by a \(1\) ppm concentration of pentavalent As. The number of electrons and holes are, respectively: (Given: \(n_i=1.5\times10^{16}~\text{m}^{-3}\))

Why can't we take one slab of p-type semiconductor and physically join it to another slab of n-type semiconductor to get a p-n junction?

The V-I characteristic of a silicon diode is shown in the figure. The resistance of the diode at ${\mathrm{I}}_{\mathrm{D}}=15 \mathrm{mA}$ is: 

$1. 20 \mathrm{\Omega }$
$2. 30 \mathrm{\Omega }$
$3. 15 \mathrm{\Omega }$
$4. 10 \mathrm{\Omega }$

The \((V\text-I)\) characteristic of a silicon diode is shown in the figure. The resistance of the diode at \(V_D=-10\) V is:${\mathrm{}}_{}$

     
1. \(1\times10^7~\Omega~\)
2. \(2\times10^7~\Omega~\)
3. \(3\times10^7~\Omega~\)
4. \(4\times10^7~\Omega~\)$\mathrm{}$

Which one of the following is not true for the photodiodes?

Which material is preferred for solar cells?
1. \(\text{Si}\)
2. \(\text{GaAs}\)
3. \(\text{CdS}\)
4. both \(\text{Si}\) and \(\text{GaAs}\)

The output waveform (Y) of the AND gate for the following inputs A and B given in the figure is:

1.
2.
3.
4.	None of these

The output waveform (\(\text{Y}\)) of the \(\mathrm{OR}\) gate for the following inputs \(\mathrm{A}\) and\(​​​​\mathrm{B}\) given in the figure is:

1.
2.
3.
4.	none of these