Auto Electrical Works Paper 3, May/June 2015

Question 2

 

AIM: To test candidates’ knowledge of lighting circuits.

 

  1. Connect the circuit as shown in Fig. 2.
  2. Ask the supervisor to check the circuit connection.
  3. With lamps L1, L2, L3, L4 and L5 in position and switches S1, S2, and S3 open, record in Table 2 the state of the lamps as either ON or OFF.
  4. Repeat step (c) for the other tests in Table 2.
  5. In test IX, comment on the intensity of Lamp L3.
  6. In test XIII, comment on the intensity of Lamp L5.
  7. State two precautions taken in carrying out the experiment.

                                                                      Table 2


Test

Condition of switches/lamps

L1

L2

L3

L4

L5

I.

S1 open, S2 open, S3 open

 

 

 

 

 

II.

S1 closed, S2 open, S3 open

 

 

 

 

 

III.

S1 closed, S2 closed, S3 open

 

 

 

 

 

IV.

S1 closed, S2 closed, S3 closed

 

 

 

 

 

V.

S1 open, S2 closed, S3 open

 

 

 

 

 

VI.

S1 open, S2 open, S3 closed

 

 

 

 

 

VII.

S1 open, S2 closed, S3 closed

 

 

 

 

 

VIII.

S1 closed, S2 open, S3 closed

 

 

 

 

 

IX.

S1 closed, S2 closed, S3 closed, L1 removed

R

 

 

 

 

X.

S1 closed, S2 closed, S3 closed, L5 removed

 

 

 

 

R

XI.

S1 closed, S2 open, S3 closed, L3 removed

 

 

R

 

 

XII.

S1 closed, S2 closed, S3 open, L2 removed

 

R

 

 

 

XIII.

S1 closed, S2 closed, S3 open, L4 removed

 

 

 

R

 

XIV.

S1 closed, S2 open, S3 closed, L5 removed

 

 

 

 

R

XV.

S1 closed, S2 closed, S3 open, L5 removed

 

 

 

 

R

                        [Hint: R indicates that lamp is removed]

Observation

 

            Table 2


Test

Condition of switches/lamps

L1

L2

L3

L4

L5

I.

S1 open, S2 open, S3 open

OFF

OFF

OFF

OFF

OFF

II.

S1 closed, S2 open, S3 open

OFF

OFF

OFF

OFF

OFF

III.

S1 closed, S2 closed, S3 open

ON

ON

OFF

OFF

ON

IV.

S1 closed, S2 closed, S3 closed

ON

ON

ON

ON

ON

V.

S1 open, S2 closed, S3 open

OFF

OFF

OFF

OFF

OFF

VI.

S1 open, S2 open, S3 closed

OFF

OFF

OFF

OFF

OFF

VII.

S1 open, S2 closed, S3 closed

OFF

OFF

OFF

OFF

OFF

VIII.

S1 closed, S2 open, S3 closed

OFF

OFF

ON

ON

ON

IX.

S1 closed, S2 closed, S3 closed, L1 removed

R

OFF

ON

ON

ON

X.

S1 closed, S2 closed, S3 closed, L5 removed

OFF

OFF

OFF

OFF

R

XI.

S1 closed, S2 open, S3 closed, L3 removed

OFF

OFF

R

OFF

OFF

XII.

S1 closed, S2 closed, S3 open, L2 removed

OFF

R

OFF

OFF

OFF

XIII.

S1 closed, S2 closed, S3 open, L4 removed

ON

ON

OFF

R

ON

XIV.

S1 closed, S2 open, S3 closed, L5 removed

OFF

OFF

OFF

OFF

R

XV.

S1 closed, S2 closed, S3 open, L5 removed

OFF

OFF

OFF

OFF

R

 

(e) It becomes brighter/ It has higher intensity                                                          
(f) It becomes brighter/ It has higher intensity                                                          
(g) Precautions in carrying out the experiment

  • Ensure tight connection
  • Ensure the correct polarity of battery
  • Switch off the circuit after recording readings and observation to

prevent battery drain.


Question 2 required candidates to connect a circuit with the provided diagram, follow a series of switching instructions and observe the lamps that were either ON or OFF at any instance. Majority of the candidates that attempted Question 2 responded very well.