Electronics Paper 2, May/June 2014  
Questions: 1 2 3 4 5 6 7 Main
General Comments

Question 3
  1. Define secondary emission.
  2. List any two anodes of a cathode ray tube.
  3. State two parameters of a triode valve.
  4. Draw and label the symbol of each of the following:

      (i)        directly heated cathode triode valve;
     (ii)         indirectly heated cathode triode valve.


 The expected answers were:
(a)        The liberation of electrons from an element other than the cathode of a valve by high velocity electrons
(b)        (i)         Focus anode
             (ii)        Accelerating anode
             (iii)       Final anode
             (iv)       First anode
             (v)        Second anode
(c)        gm = transconductance
             amplification factor
             ra  =  anode resistance

The question was on Electron Emission. The question was attempted by many candidates. Many confused the parameters transconductance/mutual conductance , plate resistance, amplification factor with the device’s electrodes which incidentally was a repeat of past question. The performance was average.

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