Elect Installation & Maintenance Work 2, WASSCE (SC), 2018

Question 1


  1. (a)       (i)        State five causes of accidents in a temporary electrical installation.
    (ii)       Name the three main types of maintenance carried out on electrical machines.
    (b)       (i)        Explain briefly each of the following terms:
    single phasing;
    electrical circuit.
    (ii)       State three requirements of IEE regulations on motors control.
    (c)       (i)        Mention the two types of analogue electrical measuring instruments.
    (ii)       State three advantages of a digital measuring instrument over an analogue measuring instrument.
    (d)       Sketch the British Standard (B.S.) symbols of each of the following electrical accessories:
    (i)        2-way switch;
    (ii)       intermediate switch;
    (iii)      13 A socket outlet.

    (e)       Mention two records that should be kept by a small-scale electrical business owner.



In part (a), candidates’ performance was fair. Many candidates had a good knowledge and understanding of the requirements. However, some candidates fail to understand and recognize that “ignorance” and carelessness are the same. Separating them as different points yield no mark.

In part (b), this was a popular question as majority of the candidates scored full mark. Performance was above average.

In part (c), many candidates had issues with the question. Performance was below average

In part (d), many candidates failed to understand that this question was not about electrical installation but as it relates to electric motors and not cars/buses. Performance was below average,

The expected answers include:

1 (ai)   Five Causes of Accidents in a Temporary Electrical Installation

    • Circuit fuse overrated
    • Cable run over sharp edges
    • Lack of protective covering on switches/joint boxes
    • Use of cable without mechanical protection/bare conductors
    • Unauthorised addition to circuit resulting in overloading with consequences of fire outbreak/risk
    • Use of unearthed brass or un-skirted lamp holders
    • Exposed metal parts
    • Horse play/carelessness
    • Use of wrong tools
    • Lack of safety wear.

            (ii)       Three main Types of Maintenance Carried out on Electrical Machines

    • Predictive
    • Preventive
    • Corrective

(bi)      Single Phasing
Is the effect produced when an open circuit occurs on one of the lines/phases supplying 3-phase motor.                                                                                                                        
Electrical Circuit
Is an arrangement of conductors and associated accessories for the purpose of carrying current.                                            
Is a closed loop through which current can flow                                          
(ii)       Three Requirements of IEE Regulations on motors Control

    • Means of starting
    • Means of stopping
    • Means of preventing automatic restarting
    • Means of protection against excess current
    • Means of protection against mechanical damage
    • The control should be easily accessible to the operators
    • Where the means of isolation is at a remote, an additional means of                                 isolation shall be provided adjacent to the motor

(ci)      Two Types of Analogue Electrical Measuring Instruments

    • Moving coil instrument
    • Moving iron instrument

(ii)       Three Advantages of a Digital Measuring Instrument Over Analogue Measuring Instrument

    • No parallax error
    • Low power consumption
    • No pointer over a calibrated scale
    • It can be used by an unskilled person/easy to read
    • Numerical readout allows many users to use it at the same time
    • It saves time
    • Data from digital instrument be recorded for future references
    • The output of the digital devices can be obtained in the computer.
    • High acccuracy

(di)      British Standard (B.S) Symbols

(e)       Two Records that should be kept by a Small-Scale Business Owner

    • Inventory/stock book
    • Daily sales record
    • Cash flow record
    • Budget
    • Invoice
    • Cash receipt
Delivery note