Q. No.In a good conductor, the energy gap between the conduction band and the valence band is:
1. Infinite
2. Wide
3. Narrow
4. Zero
In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is a/an:
| 1. | \(\mathrm{p}\text-\)type semiconductor |
| 2. | insulator |
| 3. | metal |
| 4. | \(\mathrm{n}\text-\)type semiconductor |
Which of the energy band diagrams shown in the figure corresponds to that of a semiconductor?
| 1. |  |
2. |  |
| 3. |  |
4. |  |
| 1. | The resistivity of a semiconductor increases with an increase in temperature. |
| 2. | Substances with an energy gap of the order of \(10~\text{eV}\) are insulators. |
| 3. | In conductors, the valence and conduction bands may overlap. |
| 4. | The conductivity of a semiconductor increases with an increase in temperature. |
In semiconductors at room temperature:
| 1. | The valence band is completely filled and the conduction band is partially filled. |
| 2. | The valence band is completely filled. |
| 3. | The conduction band is completely empty. |
| 4. | The valence band is partially empty and the conduction band is partially filled. |
Carbon, Silicon, and Germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy gaps represented by \(\left(E_g\right)_C,(E_g)_{Si}~\text{and}~(E_g)_{Ge}\) respectively. Which one of the following relationships is true in their case?
1. \(\left(E_g\right)_C<\left(E_g\right)_{G e} \)
2. \(\left(E_g\right)_C>\left(E_g\right)_{S i} \)
3. \(\left(E_g\right)_C=\left(E_g\right)_{S i} \)
4. \(\left(E_g\right)_C<\left(E_g\right)_{S i}\)
| 1. | in the case of \(\mathrm{C},\) the valence band is not completely filled at absolute zero temperature. |
| 2. | in the case of \(\mathrm{C},\) the conduction band is partly filled even at absolute zero temperature. |
| 3. | the four bonding electrons in the case of \(\mathrm{C}\) lie in the second orbit, whereas in the case of \(\mathrm{Si},\) they lie in the third. |
| 4. | the four bonding electrons in the case of \(\mathrm{C}\) lie in the third orbit, whereas for \(\mathrm{Si},\) they lie in the fourth orbit. |
| 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. |
A semiconductor is known to have an electron concentration of \(8\times 10^{13}~\text{cm}^{-3},\) and a hole concentration of \(5\times 10^{2}~\text{cm}^{-3}.\) The semiconductor is:
| 1. | \(\mathrm{n}\text-\)type | 2. | \(\mathrm{p}\text-\)type |
| 3. | intrinsic | 4. | insulator |
How much is the forbidden gap (approximately) in the energy bands of germanium at room temperature?
1. \(1.1~\text{eV}\)
2. \(0.1~\text{eV}\)
3. \(0.67~\text{eV}\)
4. \(6.7~\text{eV}\)
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