PHYSICS CH8

a silicon crystal is doped with atoms of a pentavalent element, so the ratio between the concentrations of holes and that of free electrons at equilibrium is........

• less than 1

• greater than 1

• equal to 1

• equal to 0

if the emitter current in an npn transistor is 1.5 mA and the collector current is 1.45 mA so the base current equals......

• 2.95 mA

• 0.55 mA

• 0.6 mA

• 0.05 mA

the region which has the lowest concentration of electric charge carries in the transistor is.........

• the base

• the emitter

• the collecter

• the three regions have the same concentrations

the hole in a semiconductor has the same charge as........

• a proton

• an electron

• a neutron

• it depends of the type of the crystal

if two different chips, one of copper and the other of germanium, are cooled down from the room temperature to 80 K, so ......

• their resistance increase

• their resistance decrease

• the resistance of copper increases while the resistance of germanium decreases

• the resistance of copper decreases while the resistance of germanium increases

the binary number which is equivalent to the summation of the following decimal number (1+1+1+1) is.......

• (1111)2

• (101)2

• (110)2

• (100)2

the n-type semiconductor crystal is......

• negatively charged

• neutral

• positively charged

• an insulator

the occurrence of electric resistance in the deletion region of the pn junction is due to the..........

• absence of free moving charge carries inside it

• presence of a large number of carries inside it

• presence of free electrons only inside it

• presence of holes only inside it

when a pn junction is connected in forward direction,...........

• the thickness of the depletion region increases

• the thickness of the depletion region doesn't change

• the thickness of the depletion region decreases

• the resistance of the junction increases

the transistor consists of.........

• one pn junction

• two pn junction

• three pn junction

• four pn junction