21) The electrode of a vacuum tube which collects the electrons is known as
a) cathode
b) grid
c) anode
d) triode
a) cathode
b) grid
c) anode
d) triode
22) The space charge effect can be overcome by the process of
a) increasing plate potential
b) increasing cathode potential
c) decreasing plate potential
d) none of the above
23) A separate heating element is used in
a) directly heated valves
b) indirectly heated valves
c) power emitters
d) none
24) The space charge in a vacuum diode is caused due to
a) a negative plate voltage
b) too high plate voltage
c) the cloud of electrons near the cathode
d) positive ions
25) solar cell is an example of
a) photo conductive device
b) photo emissive device
c) photo voltaic device
d) all
26) The control grid in a triode is which potential with respect to cathode
a) negative
b) positive
c) either a or b
d) none
27) Vacuum tubes are which devices
a) linear
b) non linear
c) unidirectional
d) both b and c
28) Important emitter materials are
a) tungsten
b) thoriated tungsten
c) oxide coated materials
d) all
29) Vacuum diode is invented by
a) deforest
b) fleming
c) brattain
d) none
30) Cathode of valves in radio is heated by
a) directly
b) indirectly
c) both
d) none
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