Question 4
- The diagram below illustrates two pieces of threaded conduits (A and B), a locknut and a socket.Study the diagram and answer questions that follow.
(i) Reproduce the diagram showing the parts coupled together.
[2 marks]
(ii) Where is this type of coupling used? [1 mark]
(iii) Why is it important to ensure that the socket is tightened firmly to the part labelled B? [1 mark] - Study the electrical workshop tools illustrated below and answer the questions that follow
(i) Identify X, Y and Z. [3 marks]
(ii) State one use each of X, Y, Z. [3 marks]
(iv) Suggestfive ways of maintaining electrical tools. [5 marks] - Identify three possible causes of each of the following faults in an a.c. motor:
(i) motor fails to start; [3 marks]
(ii) overheating while running. [3 marks]
Observation
This is a test of practical question. Few candidates understood the demands of the question.
In part (a), few candidates could reproduce the diagram by showing the parts coupled together. However, majority of the candidates listed the tools that could be used for the coupling process.
In part (b), majority of the candidates were able to identify tools X, Y and Z.
In part (c), majority of the candidates could not identify the listed faults in an a.c. motor.
The expected answers include:
- (i)
(ii) - steel/metal conduit system of wiring
(iii)- to prevent mechanical damage of the conduit
- to avoid loosening of the locknut from socket
(iv) - torque range
- spanner
- wrench - (i) ELECTRICAL WORKSHOP TOOLS
X –(pair of) pliers
Y - screw driver
Z – hammer
(ii) X / it is used for holding / gripping / twisting / cutting (cables)
Y / it is used for driving screw in and out
Z / it is used for driving in nail
(iii) - handle
- teeth
- body
(iv)WAYS OF MAINTAINING ELECTRICAL TOOLS
- keep in dry place / keep away from moisture
- keep clean after use
- keep them in their proper boxes / racks
- use a particular tool for the job it is meant for / do not use wrong tools for a job
- oil/grease/ lubricate tools
- sharp/grind tools when blunt - (i) CAUSES OF FAULTS IN AN A.C. MOTOR
- failure of supply/no supply
- short circuit
- open circuit in control gear
- incorrect setting of over – current releases
- faulty centrifugal switch
- open circuited fuse
(ii) - overloading
- single phasing / supply voltage not available in one of the three terminals
- short circuit
- worn bearing
- ground/earth fault