Question 7
- Explain the term servomechanism.
- State three physical quantities that are controlled by closed loop systems.
- State three appliances that use thermostatic sensing control.
- State two effects of negative feedback in a closed loop control system.
Observation
The expected responses were:
- A servomechanismis basically a negative feedback control device, which automatically controls a large output (physical quantity -usually position or speed) using a much smaller corresponding input signal
- Physical quantities controlled by closed loop systems
- Position
- Speed
- Fluid level (or volume)
- Temperature (or heat)
- Light intensity
- Pressure
- Appliances which utilizes thermostatic sensing
- Electric iron
- Air conditioner
- Refrigerator (or deep freezer)
- Water heater
- Oven
- Boiler
- Hot plate burner
Question 7 required candidates to show basic knowledge of servomechanism and control systems. The Chief Examiner noted that majority of the candidates that attempted question 7 confused physical quantities with devices.