Elect Installation & Maintenance Work 2, WASSCE (SC), 2019

Question 4



  1. The diagram above illustrates an electric lamp. Study it carefully and answer the following questions.


    1. Name the parts labelled V, W, X, Y and Z.

    2. What type of lamp does the diagram illustrate?

    3. State one function each of the parts labelled V and Z.

    4. Name the gas used in filling the lamp.

    5. State three possible faults that could make the lamp not to light when switched on.

  2. Figs. 1.1, 1.2 and 1.3 illustrate three lamps, three one-way switches and a joint box respectively. Study the symbols and answer the following questions.


    1. Using Figs. 1.1, 1.2 and 1.3, draw the wiring diagram showing each lamp controlled independently by it.

    2. State three precautions to be taken when carrying out the wiring on a wiring board.

    3. List five materials needed in carrying out the wiring on a wiring board.

    4. State the standard required cable size that can be used when carrying out the wiring on a wiring board.

Observation


Performance was below average. Many candidates failed to understand that wiring board is a miniature house, hence every precaution must be observed.


The expected answers include:


    1. Labelled Parts of an Electrical Lamp
    2. V - (Coiled-Coil) filament


      W - Bulb


      X - Gas-filled interior/inert gas


      Y - Insulation/insulator/cap/base/holder


      Z - Contacts


    3. Type of Lamp illustrated in 4(a)(i)
    4. Incandescent lamp/filament lamp (bulb)


    5. Functions of V and Z
    6. V - it converts electrical energy to light energy/it is the part that glows/produce light


      Z - it connects/links the lamp to the source of supply/energy


    7. Name of the gas used in filling the Lamp


      Inert gas/argon

      .
    8. Possible Faults that could make the Lamp not to Light When Switched on
      • Open circuit.


      • Broken filament/damage element.

      • Poor contact on terminals/pins.

      • Broken/cracked bulb/lamp.

      • Short circuited terminals/pins.

      • Gas may have been used up.

      • Faulty lamp holder.

    1. Wiring Diagram Showing Each Lamp Controlled Independently by Corresponding Switch


    2. Precautions for Wiring on a Wiring Board

      • Ensure usage of correct tools

      • Ensure tight connections (to avoid partial contact).

      • Ensure that live that is coming from the supply is taken to the switches (and the neutral to the lamp).

      • Ensure usage of correct cable size.

      • Isolate the supply from the installation when wiring.

      • Avoid short circuiting

      • Avoid the use of uninsulated tools.

    3. Materials Needed for Wiring on a Board

      • Cable (PVC).

      • Clip/saddle.

      • Brass nails.

      • Screw.

      • Insulation tape.

      • Conduit pipe.

      • Pattress.

    4. Cable Size 1.5 mm2