Changing number of charge carriers

Question 1

How can we change the amount fo charge carriers and hence ability to conduct?

Answer 1

Changing temperature

adding or removing the impurity atoms

Question 2

What does the valence and conduction band look like for metals?

Answer 2

Overlapping bands

Question 3

Is the drift velocity for metals small or big?

Answer 3

Small, as there is a lot of charge carriers

Question 4

What happens if we increase the temperature for metals

Answer 4

• we increase the amplitude of vibrations of the ions within the lattice, causing more frequent collisions with the charge carriers, hence resistance increases
• no extra charge carriers are released

Question 5

What is the number of charge carriers for an insulator?

Answer 5

0

Question 6

What happens when temperature is increased for an insulator?

Answer 6

Nothing

Due to the high energy requirement to release carriers of the material , it is destroyed before conduction can happen

Question 7

What do the bands look like for an insulator?

Answer 7

Massive gap between valence and conduction band

Question 8

How many charge carriers do semiconductors have? what is the drift velocity

Answer 8

fewer than metals, so their drift velocity is higher

Question 9

What do the bands look like for semiconductors?

Answer 9

small gap between bands

Question 10

What is a valence band?

Answer 10

charge carrier energy level that keeps carriers close to the nucleus

Question 11

What is a conduction band ?

Answer 11

charge carrier energy level at which carrier is delocalised and free to carry charge