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Question 1

Define the following:

a) . Conductor
b) .Semiconductor
c) . Insulator

Answer 1

Answers:

a) . a conductor is a material whih allows for an un-hindered flow of electrons through the lattice.
b) . materials with electrical conductivity between that of a conductor and an insulator, including silicon and germanium.
c) . a material which lattice’s structure hinders the flow of electrons.

Question 2

Describe how electrical charges move in a metal.

Answer 2

Metal Lattices, consist of an orderly array of positive metal ions.

To maintain stability, the valence electrons are free to move like a cloud of negative charges throughout the lattice, which then efficiently conduct electricity through the lattice.

Question 3

Define the following terms:

a) . energy band
b) . valence band
c) . conduction band
d) . forbidden energy band

Answer 3

Answers:

a) . In semi-conductors, the atoms are very close together, their highest energy levels are called energy bands.
b) . The valence band is the energy band in a solid in which the outermost electrons are found.
c) . The conduction band lies above the valence band is where the electrons jump (over the energy gap) when conduction is attempted.
d) . The forbidden energy gap is the space between the conduction and valence energy bands, where 0 electrons are found.

Question 4

Account for the presence of the forbidden energy band.

Answer 4

The forbidden energy gap is what seperates a conductor from an insulator. If there is little to no energy gap, the material is a conductor, however the presence of an energy gap makes it an insulator or a semi conductor

Question 5

Define the following terms:

a) . electron
b) . hole

Answer 5

Answers:

a) . an electron is a sub-atomic particle with a negative charge
b) . holes represent the absence of an eletron in an energy level. They are formed when elements, such as silicon, are doped.

Question 6

Using an Analogy, describe the movement of holes in semi-conductors.

Answer 6

Using students and chairs, an analogy for the movement of electron holes can be described. As the students line up, sitting in chairs (in single file) they move from right to left one chair at a time. When a studnet reaches the last chair, they then move back into the first chair and the process repeats. For a brief moment a chair is vacant thus representing a “hole” that is then filled by a student or an “electron”. These holes move in the opposite direction to the electrons (students)