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Electronics Paper 2, May/June 2008  
Questions: 1 2 3 4 5, 6 & 7 8 9 10 Main
General Comments
Weakness/Remedies
Strength
Question 10

(a) State two conditions on which closed-loop control system operates.
(b) State the type of control system applied in the following appliances;
          (i)            electric fan
          (ii)           electric cooker 
          (iii)          electric iron
          (iv)         T.V. remote control.
(c) State the type of control system applicable in the following cases:
          (i)            a car being driven on a highway.
          (ii)           aeroplane landing on autopilot.

_____________________________________________________________________________________________________
OBSERVATION

The expected answers were:
(a) A closed-loop control system will carry out the desired control function when
           -              There is a feedback signal.
           -              The feedback signal is different from that of  the reference signal.
(b        

Appliance

Control Type

Electric fan

Open Loop

Electric cooker

Open Loop

Electric Iron

Closed Loop

TV remote control

Open Loop

(c)           i               The motor car being driven on a highway – closed loop(with driver constituting part                                    of the loop).
                  Ii              Aeroplane landing on autopilot – closed loop.

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