Pre-Rehearsal Exam, Physics 12

Name, Father Name, Adm: No.

When the forbidden energy gap between the valence band and conduction band is very small then the material is -----

• conductor

• insulator

• semiconductor

• super conductor

In insulator, the top most valence band is ----------

• partially filled

• completely filled

• empty

• half filled

In free electron theory, the electron in metal is assumed to be free of

• surface

• whole substance

• of the concerned nucleus

• none of these

What determines, in terms of energy bands, whether a substance is a good conductor, semiconductor or insulator?

• The size of conduction band

• the size of valence band

• the size of the forbidden band

• the name of the material

which superconductor was discovered in 1986?

• mercury

• porcelain

• thallium

• ceramic

In a transistor, collector current is controlled by ----

• base current

• collector voltage

• collector resistance

• all of the above

most of the electrons in the base of an NPN transistor flow ---

• into the collector

• out of the base lead

• into the emitor

• into the base supply

The section of transistor that supplies charge carriers is called ----

• collector

• emitter

• base

• none of these

The amplification role of transistor is hidden in the size of --

• the base

• the emitter

• collector

• all of these