waecE-LEARNING
Electronics Paper 2, Nov/Dec. 2011  
Questions: 1 2 3 4 5 6 7 8 9 10 Main
General Comments
Weakness/Remedies
Strength















Question 10

(a)    

) Draw a labeled block diagram of a closed-loop control system showing
the direction of signal flow.
(b) State three domestic appliances that use the closed-loop control
system.

_____________________________________________________________________________________________________
OBSERVATION

T

The expected answers were:

(a)       Labelled block diagram of control system

Referenc
input

e

+

Comparator

..

I Controller

1

 

 

 

 

 

 

I

I

~

 

 

 

 

 

 

 

 

 

 

 

 

-

 

 

 

 

 

 

 

 

Feedback

 

Feedback

 

 

 

 

 

signal

 

 

network

 

 

 

 

Actuating
signal

Controlled
output

(b)       (i)        Refrigerator
           (ii)        Pressing iron
            (iii)       Air conditioner
            (iv)      Any other

The question was on Control Circuits. The question was unpopular. The
performance of the very few candidates that attempted it was reportedly
poor.


                       

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