Observation

 

                     
1(a): It is evident that the candidates possess a good understanding of the concept of open and closed   circuit voltage, as most of them were able to define it accurately.
1(b): The candidates' performance was deemed fair, as the majority of them were unable to identify the causes of faults in d.c. generators.
1(c): Most candidates were able to list materials used for surface wiring.
1(d): Candidates performed well in (i) but poorly in (ii) as most of them could not state the methods of   measuring efficiency of a battery.

1(e): The majority of candidates demonstrated a credible performance in this section

Expected response:

1.     EXPLANATION OF TERMS USED IN ELECTRICAL INSTALLATION
1. Open circuit voltage

                            It is the voltage when there is no load/offload voltage
OR It is the voltage when current is NOT flowing through the load

1. Closed circuit voltage;

                            It is the voltage when there is load /is the voltage on load
OR  It is the voltage when current is flowing      

1. CAUSES OF FAULTS IN A D.C GENERATOR
1. NO OUTPUT
1. Sticking brushes
2. Corroded commutator
3. Shorted/open armature
4. Shorted/open field
5. Dirty commutator
6. Defective AVR
7. Tripped breaker
8. Blocked/Faulty excitation circuit
9. Loss of residual magnetism
10. Broken conductor

1. LOW OUTPUT
1. Loose or worn drive belts
2. Low brush spring tension
3. Dirty commutators
4. Corroded commutator
5. Worn commutator
6. Low voltage on the alternator
7. Loss of residual magnetism on the alternator

 

1. NOISY GENERATOR
1. Loose mounting
2. Loose pulley
3. Worn or dirty bearings
4. Weak brush spring
5. Faulty/broken radiator fan
6. Broken/loose exhaust pipe/silencer

1. MATERIALS USED FOR SURFACE WIRING
2. Cables
3. Clips
4. Nails (screw, brass, concrete)
5. Insulation tape
6. Rawl plug
7. Wooden block
8. Boxes
9. Consumer unit
10. Connector
11. Switch
12. Socket
13. Ceiling rose
14. Joint box
15. Lamp holder

    

1. (i)        WAYS OF MAINTAINING A LEAD-ACID BATTERY
2. Re-charge battery when voltage and specific gravity fall
3. Recharge battery regularly even if not in use
4. Electrolyte should not be added to a battery unless there is a spillage
5. Battery should be kept topped up with distilled water above plate level
6. Do not overcharge, boost charge or over discharge a battery
7. Always allow battery to charge fully
8. Always check cable, plugs and chargers regularly
9. Disconnect cable from battery terminals when not in use

1. METHODS OF MEASURING THE EFFICIENCY OF A BATTERY
1. The ampere-hour efficiency
2. The watt-hour efficiency
3. Columbic efficiency
4. Voltage efficiency

 

1. PROCEDURES FOR RESCUING A VICTIM OF ELECTRIC SHOCK
2. Switch off supply
3. Remove victim from the danger with an insulated material
4. Remove any obstructions to breathing
5. Commence artificial respiration
6. Call a medical personnel