waecE-LEARNING
Electronics Paper 2, Nov/Dec. 2012  
Questions: 1 2 3 4 5 6 7 8 9 10 Main
General Comments
Weakness/Remedies
Strength















Question 8

(a)     Figure 6 is a half voltage doubler circuit

Figure 6

(a) Show the direction of the current flow for each half cycle of the input
signal.
(b) State the function of the
       (i)        passive components;
       (ii)       active components.

_____________________________________________________________________________________________________
OBSERVATION

The expected answers were:

 

(a)

(i)

First half cycle

 

 

 

 

 

 

C1

D2

 

 

 

~-

 

 

 

 

 

 

 

 

)

 

C2

 

 

 

+

 

(ii)

Second half cycle

 

C1




 

C2
+



321



                                                              1            C1

           (b)        (i) Functions of passive components - C1,C2 and transformer.
Transformer steps (up or down) the input voltage to the required
value. C1 and C2 store charges to maintain Vpeak during conducting
half cycle of D1 and D2 and discharge the charge during the non-
conducting half cycle.
(ii) Active components
D1 and D2 conduct alternate half cycle and charge C1 or C2 to
produce required Va.

As reported, very few candidates who attempted it gave poor responses
suggesting ill-preparation. The question was on Power Supply. The
question was unpopular and candidates performed poorly in it.

 

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