The expected responses were:

(a) (i)   Applications of thermionic emission

• Vacuum tubes
• CRT (in television sets and oscilloscope)
• X – rays
• Fluorescent tubes

    (ii)    Applications of photo emission

• Photocells
• Solar cells
• Burglar alarms
• Television cameras
• Automatic door switching
• Automatic light switching devices
• Fibre optic communication

 (b)       X – screen grid                       
          Y – control grid                                                            

(c)        Advantages of semiconductor devices over vacuum tubes

• Much smaller size
• No/less heat production
• Longer life span
• Faster response time
• Lower power consumption

It was reported that quite a few candidates had problems recalling the applications of thermionic emission and photo emission in part (a). Part (b)is essentially a ‘recall’ type question, for the question on pentode, so that X represented the screen grid, and Y, the control grid. The Chief Examiner reported that many candidates listed these correctly, quite a few mixed them (one for the other) and still many could not correctly identify the grids. Performance in the question (c) was rated rather poor.