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

1.	because ionization energy for \(\mathrm{C}\) is the least in comparison to \(\mathrm{Si}\) and \(\mathrm{Ge}\).
2.	because ionization energy for \(\mathrm{C}\) is highest in comparison to \(\mathrm{Si}\) and \(\mathrm{Ge}\).
3.	the number of free electrons for conduction in \(\mathrm{Ge}\) and \(\mathrm{Si}\) is significant but negligibly small for \(\mathrm{C}\).
4.	both (2) and (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 \((V\text-I)\) characteristic of a silicon diode is shown in the figure. The resistance of the diode at \(V_D=-10~\text V\) is:${\mathrm{}}_{}$

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

Carbon, Silicon, and Germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by ${\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{C}},{}_{}$ ${\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{Si}}$, and ${\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{Ge}}$ respectively. Which one of the following relationships is true in their case?

1. ${\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{C}}<{\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{Ge}}$

2. ${\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{C}}>{\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{Si}}$

3. ${\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{C}}={\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{Si}}$

4. ${\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{C}}<{\left({\mathrm{E}}_{\mathrm{g}}\right)}_{\mathrm{Si}}$

Let \(n_{p}\) and \(n_{e}\) be the number of holes and conduction electrons in an intrinsic semiconductor. Then:
1. \(n_{p}> n_{e}\)
2. \(n_{p}= n_{e}\)
3. \(n_{p}< n_{e}\)
4. \(n_{p}\neq n_{e}\)

A \(\mathrm{p}\text-\)type of semiconductor is:
1. positively charged
2. negatively charged
3. uncharged
4. uncharged at \(0~\text{K}\) but charged at higher temperatures

When an impurity is doped into an intrinsic semiconductor, the conductivity of the semiconductor:
1. increases
2. decreases
3. remains the same
4. becomes zero

In a semiconductor;