Auto Electrical Works Paper 2, WASSCE (SC), 2022

Question 4

 Fig.3 shows the schematic diagram and basic electrical layout of the essential elements of a motor vehicle electrical system.

  1. State the function of the:
  2. alternator;
  3. regulator;
  4. battery.
  5. Table 3 contains systems of motor vehicle. Complete it by stating one long-term effect a loose belt tension of the system in Fig. 3 will have on each of the systems in systems in Table 3.

                                                               Table 3


S/N

System

Long-term effect of loose belt tension

(i)

Ignition system

 

(ii)

Starting system

 

(iii)

Lighting system

 

(iv)

Auxiliary system

 

  1. Use Fig. 3 to briefly explain the principle of operation of a charging system.

The expected responses were:

  •  (i)  Functions of the alternator in figure 3
  • Serves as source of power
  • Generates alternating current

                                                                                                                       
(ii)    Functions of the regulator in figure 3

  • Stores power
  • Supply  direct current to the system

    (iii)  Functions of the battery in figure 3

  • Ensures constant supply to charge  the battery

                                                                        

  •                                                              Table 3          

S/N

System

long-term effect of loose belt tension

(i)

Ignition system

failed ignition

(ii)

Starting system

failed starting system

(iii)

Lighting system

no light /dim light

(iv)

Auxiliary system

failed auxiliaries

 

 

 

  • The principle of operation of a charging system using Figure 3
  • When engine is not running the alternator voltage is less than the battery voltage so current flows from the battery to the vehicle load, the alternator diode prevent current flowing into the alternator.
  • When engine is running the alternator output is greater than the battery voltage, current flows from the alternator to the vehicle loads as well as the battery. This implies the alternator output is always greater than the battery voltage during operation of the engine.

           
Question 4 required candidates to show understanding of how component parts of a charging system function.. It was reported that majority of the candidates that attempted question 4 could not state the function of the component part nor could they explain the principle of operation of a charging system.