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∘K.0∘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) and (B) only |
2. | (B) and (C) only |
3. | (A), (C), and (D) only |
4. | (A), (B), and (D) only |
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 (Eg)C, (Eg)Si, and (Eg)Ge respectively. Which one of the following relationships is true in their case?
1. (Eg)C<(Eg)Ge
2. (Eg)C>(Eg)Si
3. (Eg)C=(Eg)Si
4. (Eg)C<(Eg)Si
C, Si, and Ge have the same lattice structure. Why is the C insulator?
1. | because ionization energy for C is the least in comparison to Si and Ge. |
2. | because ionization energy for C is highest in comparison to Si and Ge. |
3. | the number of free electrons for conduction in Ge and Si is significant but negligibly small for C. |
4. | both (2) and (3). |
Hole is:
1. | an anti-particle of electron. |
2. | a vacancy created when an electron leaves a covalent bond. |
3. | absence of free electrons. |
4. | an artificially created particle. |
Let np and ne be the number of holes and conduction electrons in an intrinsic semiconductor. Then:
1. np>ne
2. np=ne
3. np<ne
4. np≠ne
A p-type of semiconductor is:
1. positively charged
2. negatively charged
3. uncharged
4. uncharged at 0 K but charged at higher temperatures
Which of the following is correct for n-type semiconductors?
1. | electron is the majority carriers and trivalent atoms are dopants. |
2. | electrons are majority carriers and pentavalent atoms are dopants. |
3. | holes are majority carriers and pentavalent atoms are dopants. |
4. | holes are majority carriers and trivalent atoms are dopants. |