1. | decreases for conductors but increases for semiconductors |
2. | increases for both conductors and semiconductors |
3. | decreases for both conductors and semiconductors |
4. | increases for conductors but decreases for semiconductors |
In a semiconductor,
(a) | there are no free electrons at \(0~\text{K}.\) |
(b) | there are no free electrons at any temperature. |
(c) | the number of free electrons increases with temperature. |
(d) | the number of free electrons is less than that in a conductor. |
1. | (a), (b) |
2. | (b), (c) |
3. | (a), (c), (d) |
4. | (a), (b), (d) |
1. | \(414\) nm | 2. | \(300\) nm |
3. | \(830\) nm | 4. | \(207\) nm |
Identify the incorrect statement from the following:
1. | The resistivity of a semiconductor increases with an increase in temperature. |
2. | Substances with an energy gap of the order of 10 eV are insulators. |
3. | In conductors, the valence and conduction bands may overlap. |
4. | The conductivity of a semiconductor increases with an increase in temperature. |
Carbon, Silicon, and Germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by , and respectively. Which one of the following relationships is true in their case?
1.
2.
3.
4.
\(\mathrm{C}\), \(\mathrm{Si}\), 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). |