waecE-LEARNING
Home
Technical
Mathematics
Languages
Science
Social Science
Art
Literature Arabic Islamic Studies C.R.K HistoryMusicVisual Art Clothing/Textile Home Management Shorthand
 
Electronics Paper 1, May/June 2008  
Questions: 1 2   Main
General Comments
Weakness/Remedies
Strength











































Question 2

  h                                  
  1. Connect the circuit as shown in Figure 1 using the silicon diodes DI, O2, 03,04­
  2. Ask the supervisor to check the circuit connection.
  3. Copy Table 1 into your answer booklet.

Table 2


Forward Polarity

 

L₁

L₂

L₃

S₂ (Open)

 

 

 

S₂ (Closed)

 

 

 

Reverse Polarity

 

L₁

L₂

L₃

S₂ (Open)

 

 

 

S₂ (Closed)

 

 

 

              
  (d) Close switch Si and open switch S₂  
  (e) Record the state of the lamps in Table 2.
  (f) Close switch S₂ and record the state of the lamps.
  (g) Open switch S₁ and reverse the polarity of the power supply.
  (h) Repeat steps (d) to (f).
  (i) Comment on the results in each case based on the action of the lamps, diodes and switches.

  

_____________________________________________________________________________________________________
OBSERVATION

The expected answers were:
                  Table 2 (V = 12v to Earth) for Forward Polarity.
                                               


Position Of Switch S₂  

Status Of L₁

Status Of L₂

Status Of L₃

Open

ON

OFF

ON

Closed

ON

OFF

ON

                                                Table 2 (V = 12v to Earth) for Reverse Polarity.
                


Position Of Switch S₂  

Status Of L₁

Status Of L₂

Status Of L₃

Open

OFF

OFF

OFF

Closed

ON

OFF

OFF

In experiment 2, which was an adaptive form of experiment 1, the state of the lamp particularly in lamp 3(L₃) was got correctly by many candidates but they failed to give the comments on the results as required in 2(i).
While a few candidates who got the states of the lamps correctly had their comments inconclusively done. It was expected that their answers would include the state o the bias of the diode.


Powered by Sidmach Technologies(Nigeria) Limited .
Copyright © 2012 The West African Examinations Council. All rights reserved.