waecE-LEARNING
Electronics Paper 2, Nov/Dec. 2014  
Questions: 1 2 3 4 5 6 7 8 9 10 Main
General Comments
Weakness/Remedies
Strength















Question 1
  • Define the term secondary emission.
  • State three parameters of a triode valve.
  • Draw and label the symbol of the following valves:
  • directly heated cathode triode;
  • indirectly heated cathode pentode.

          The expected answers were:

  • Secondary emission is the process in which electrons (in motion) striking an electrode give that kinetic energy to the electrode such that other electrons are emitted by the impact.
  • Parameters
  • ­amplification factor (µ)
  • a.c. plate resistance (ra)
  • mutual conductance or transconductance (gm)

 (c)

Electronic Image

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OBSERVATION

The question was on Electron Emission and Thermionic Devices. It was quite unpopular with the candidates. On average, the performance was low mainly because many candidates appeared to be unfamiliar with the triode parameters.

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