Basic Electronics Paper 2 WASSCE (PC), 2019

Question 4


  1. explain the following:

    1. Command.

    2. Controlled variable.

    3. Classify the following devices into open loop or closed loop control systems.
      1. Gas cooker

      2. Microwave oven

      3. Bathroom water heater

      4. Deep freezer

      5. Stopwatch

      6. Soldering iron

 


Observation

 

The Chief Examiner reported that majority of the candidates could not recall the relationship between the various d.c. current flows in a bipolar junction transistor.

The expected responses were:


    1. Command refers to the reference or input signal

    2. Controlled variable indicates output signal,


  1. Classification into open loop and closed loop control systems

    Open loop control system Closed loop control system
    Closed loop control systemGas cooker Deep freezer
    Microwave oven
    Bathroom water heater
    Stopwatch
    Soldering iron