Band Theory and Types of Solids

Q.

The electrical conductivity of silicon increases by replacing a fraction of silicon atoms by arsenic atoms. Give appropriate reasons to support the statement.

Q.

Do alkali metals conduct electricity?

Q. Which of the following statement is correct regarding electrical conductivity of a semiconductor?

1. Decreases with the rise in temperature
2. Increases with the rise in temperature
3. First increases and then decreases with the rise in its temperature
4. Does not change with the rise in its temperature

Q. Which of the following represents correct order of conductivity in solids?

1. metals > insulators< semiconductors
2. metals< insulators < semiconductors
3. metals >semiconductors >insulators
4. metals insulators

Q.

The material used for coating on electric wires to avoid electric shock is __________.

1. conductor

2. insulator

3. semiconductor

4. superconductor

Q.

The material used for coating on electric wires to avoid electric shock is __________.

1. conductor

2. insulator

3. semiconductor

4. superconductor

Q. Which of the following statement is correct regarding band theory?

1. For semiconductors, small energy gap is there between conduction band and valence band
2. For conductors, no energy gap is there between conduction band and valence band
3. For insulators, large energy gap is there between conduction band and valence band
4. All of the above.

Q. What is the order of Band gap in between substances given below. Silver, silicon, glass.

1. Silver$>$Silicon$>$glass
2. glass$>$Silicon$>$Silver
3. glass$>$Silver$>$silicon
4. Silver $>$ glass $>$silicon

Q. Assertion: Electrical conductivity of semiconductors decreases with increasing temperature.
Reason: With increase in temperature, large number of electrons from the valence band can jump to the conduction band.

1. If both assertion and reason are true and the reason is the correct explanation of the assertion.
2. If both assertion and reason are true but reason is not the correct explanation of the assertion.
3. If assertion is true but reason is false.
4. If assertion Is false but reason is true.