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 |
(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 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.
, , and have the same lattice structure. Why is the insulator?
1. | because ionization energy for is the least in comparison to and . |
2. | because ionization energy for is highest in comparison to and . |
3. | the number of free electrons for conduction in and is significant but negligibly small for . |
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 and be the number of holes and conduction electrons in an intrinsic semiconductor. Then:
1.
2.
3.
4.
A type of semiconductor is:
1. positively charged
2. negatively charged
3. uncharged
4. uncharged at but charged at higher temperatures
Which of the following is correct for -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. |