\(\mathrm{C}\), \(\mathrm{Si}\), 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 \((V-I)\) 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. Si
2. GaAs
3. CdS
4. both Si and 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