16. Thermionic emission of electrons is the release of electrons
from their original material by
a.
force of collision with an incoming stream of electrons.
b.
cold-cathode ionization action.
c.
application of heat.
d.
chemical action.
17. The indirectly heated cathode has an advantage over the directly
heated cathode in that it can
a.
provide almost instantaneous operation.
b.
operate from either an ac or a dc source.
c.
use oxide-coated emitters, which are more economical.
d.
provide a constant
temperature
despite
fluctuations
in
heating current.
18. What filament material provides the greatest durability and can
withstand overloads when used in thermionic tubes?
a.
Tungsten.
b.
Thoriated tungsten.
c.
Oxide-coated nickel.
d.
Nickel-coated platinum.
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