- Metals are made up of a structured array of positive ions. The valence electrons are 'delocalised', i.e.
Your answer:
free to move like a cloud and able to conduct electricity
free to move like a cloud and not able to conduct electricity
held tightly and not able to conduct electricity
held tightly and able to conduct electricity
- If an electric field is applied to the random motion of the electrons, the electrons begin to drift in the _______ direction as/to the electric field.
Your answer:
- A semiconductor is a material in which resistance DECREASES as its temperature rises.
Your answer:
TrueFalse
- Which type of material has a valence band which is only partially filled with electrons that are free to move?
Your answer:
insulator
conductor
semiconductor
superconductor
- The highest energy band occupied by electrons is the valence band. In a conductor, the valence band is also the __________ band. (one word)
Your answer:
- A solid ionic crystal such as sodium chloride is an insulator.
Your answer:
TrueFalse
- Which of the following describes a semiconductor?
Your answer:
Valence band partly filled, Conduction band overlapping valence band; Small energy gap.
Valence band almost filled, Conduction band just separated from valence band; Small energy gap.
Valence band completely filled, Conduction band well separated from valence band; Large energy gap.
Valence band almost filled, Conduction band well separated from valence band; Very small/non-existent energy gap.
- In a semiconductor, increased thermal energy causes electrons to move from the valence band to the _________ ________. (two words)
Your answer:
- At absolute zero, all of the outer electrons in a semiconductor are in the valence band and the material acts as an insulator.
Your answer:
TrueFalse
- A positive flow of current is the movement of
Your answer:
protons moving from one atom to the next
positive ions in the lattice
holes in the valence band left by electrons
electrons in the conduction band
- What is the name given to an impurity atom that is put into a crystal lattice to change its electrical properties?
Your answer:
- The speed of hole current is greater than the speed of electron current.
Your answer:
TrueFalse
- What name is given to a material that is a naturally occurring semiconductor but has been doped to change its properties.
Your answer:
extrinsic
internal
external
intrinsic
- Nearly all semiconductors used in electronics these days are doped and are based on which element?
Your answer:
- The most often used semiconductors are found in Group 4 of the periodic table.
Your answer:
TrueFalse
- According to quantum theory, the energy of each electron in a crystal lies in well defined bands. When a semiconductor such as Silicon is heated, electrons jump the energy gap from the valence band to the conduction band, leaving a hole. If an electron from Silicon did this, how many valence electrons would remain with the hole?
Your answer:
five
two
three
four
- Germanium was commonly used in early transistors because of a lack of ability to produce other materials of suitable ________. (one word)
Your answer:
- Which of the following is a disadvantage of using Silicon in electronic components?
Your answer:
it is not very plentiful
it gets too hot and allows too much current to flow
it is difficult to purify
it does not maintain its semiconductor performance as temperature changes
- Elements from which group on the periodic table would be used to produce excess negative charge carriers in n-type semiconductors? (write the numeral)
Your answer:
- Which of the following elements could be used to dope a p-type semiconductor to produce holes to act as positive charge carriers?
Your answer:
Phosphorus
Silicon
Indium
Germanium