NATIONAL CERTIFICATE (VOCATIONAL) ELECTRONICS NQF LEVEL 2 SUPPLEMENTARY EXAMINATION 2010

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1 NTIONL ERTIFITE (VOTIONL) ELETRONIS NQF LEVEL 2 SUPPLEMENTRY EXMINTION 2010 ( ) 17 March (X-Paper) 09:00 12:00 Non-programmable calculators may be used. This question paper consists of 10 pages. opyright reserved

2 ( ) -2- N800(E)(M17)V TIME: 3 HOURS MRKS: 150 INSTRUTIONS N INFORMTION nswer LL the questions. Read LL the questions carefully. Number the answers according to the numbering system used in this question paper. IE symbols must be used in all the logic gates. Non-programmable calculators may be used to do calculations. Write neatly and legibly. opyright reserved

3 ( ) -3- N800(E)(M17)V SETION QUESTION Various options are provided as possible answers to the following questions. hoose the correct answer and write only the letter ( ) next to the question number ( ) in the NSWER OOK Its strength is directly proportional to both the number of turns in the coil and the amount of current passing through the coil: Magnetic flux lines Permanent magnet Magnetic field Electromagnetic field (1) t room temperature, very few electrons have enough energy to leap between the shells, which is necessary for conduction: Extrinsic semiconductor epletion region Insulator Intrinsic semiconductor (1) When the current flows through it, a safety switch in the main electrical circuit will turn off the supply of electricity: Earth wire Insulator Live wire Electrical equipment (1) It is an instrument that is used for measuring the electric power or the supply rate of electrical energy of any given circuit: Voltmeter Watt meter Ohmmeter mmeter (1) It is used together with the soldering iron to remove solder from the joints that have already been soldered: Solder Nozzle Solder sucker Solder wick (1) opyright reserved

4 ( ) -4- N800(E)(M17)V One of the important guidelines in preparing your work area involves one of the following: Select the components you need Plan to do the task that is required omplete the job or task raw any diagram that you may need to guide you (1) The truth table for a three input NN gate will have the following number of combinations: (1) It is used to enter the instructions in the PL: n operator interface programming device Field device n actuator (1) The first electric telegraph as a communication system was invented in by Joseph Henry (1) This is one way the WNs can be connected together as computer networks: The star networks The data networks The local area networks ell relay (1) opyright reserved

5 ( ) -5- N800(E)(M17)V 1.2 Indicate whether the following statements are TRUE or FLSE. Write only 'true' or 'false' next to the question number ( ) in the NSWER OOK When the magnetic lines of flux move in the opposite direction they attract each other. (1) When a capacitor is placed in the circuit with an source, the voltage across it remains unchanged for some time. (1) When you free a victim of an electrical shock, do try to move a victim touching a high voltage wire. (1) When removing batteries from the test instrument, make sure the instrument is connected to an external circuit before replacing the batteries. (1) cold joint occurs when the joint is moved before the solder is completely cooled. (1) The solder wiggle test is simply done by using the eraser end of a pencil to gently wiggle each component to see if it starts to work. (1) The three basic functions of oolean algebra are called N, OR and NOT. (1) Some PL input devices are sensors or transducers that convert external signals into data, for example, using an analogue-to-digital converter. (1) The process of modulation is to vary some parameter of a basic electromagnetic wave usually called the modulated wave. (1) Interference occurs when the reception of broadcast signals is clear. (1) opyright reserved

6 ( ) -6- N800(E)(M17)V 1.3 hoose a word from OLUMN that matches a description in OLUMN. Write only the letter ( J) next to the question number ( ), in your NSWER OOK. OLUMN OLUMN Generators are used at this source to generate electricity by burning oil, coal and gas in large furnaces to heat water multimeter short circuit When an electron gains enough energy to jump to the next shell of its parent atom, it leaves this gap behind NOR wire strippers These are worn in instances where there is danger of the hand and arm injury from electric shocks and burns E F drum jumper cables This instrument is used to measure voltage, current, resistance and other electrical measurements G H pathway NN They are used for making bends and loops in the conducting wire It is highly influenced by changes and developments in technology, as the maximum circuit efficiency is restricted by the components that are placed on the board The output of this logic gate will be 0 only if all inputs are 1. If not, the output will be logic 1 These are used to connect the computer to the PL to allow data to be transferred from the programmer to the processor I J K L M N O P power station circuit design hole connector cables rubber gloves amperage series round nose pliers Early fax machines would rotate it so that the photo sensor could examine one line of the sheet of paper and then move down a line Failure of an electrical system caused by bad wires or a fault in the connection in the wires or components (10 2) [20] opyright reserved

7 ( ) -7- N800(E)(M17)V 1.4 omplete the following sentences by filling in the missing word(s). Write only the missing word(s) next to the question number ( ) in the NSWER OOK is the ability of certain materials to attract or repel other materials. (1) In there is the same voltage across each of the resistors, but the current flow splits into the different branches. (1) dding arsenic also reduces the between the valence and the conduction band. (1) ll appliances have protective cords and coverings to keep you from coming into contact with electricity. (1) s a precaution when using a voltmeter, always select the range if you are not sure of the voltage magnitude. (1) Testing the joint for functionality, press the meter onto the tracks of each end of the component. (1) gives details and instructions about the work that you need to do on a component or a piece of equipment. (1) PL consists of input modules, a(n) and output modules. (1) Examples of a(n) are system drives, such as floppy discs, hard drives and optical drives. (1) is when unwanted signal interferes or affects nearby signal. (1) TOTL SETION : 50 opyright reserved

8 ( ) -8- N800(E)(M17)V SETION QUESTION 2: FUNMENTLS OF ELETRIITY 2.1 Name TWO types of magnets. (2) 2.2 Two resistors of 20 ohms and 30 ohms are connected in parallel. This parallel combination is connected in series with a third resistor of 25 ohms. The whole circuit is then connected across a 50 volt supply. etermine the following: The total resistance of the circuit (2) The current drawn from the supply (1) The volt drop across the 25 ohms resistor (2) The volt drop across the parallel branch (1) The current flow across the 20 ohms resistor (1) The current flow across the 25 ohms resistor (1) QUESTION 3: SI ELETRONI THEORY N ONEPTS 3.1 riefly explain what happens when a changing current passes through an inductor. (2) 3.2 Explain, with the aid of a sketch, how you would forward bias a P-N junction. (6) 3.3 raw a symbol of an iron core inductor. (2) QUESTION 4: ELETRIL SFETY STNRS 4.1 List FIVE safety tips to keep in mind when you are using electricity near water. (5) 4.2 Name SIX steps you will follow to treat a victim after an electrical shock. (6) 4.3 escribe FOUR causes of electrical accidents and electrical shock. (4) [15] QUESTION 5: USE N RE OF HN HEL ELETRIL TEST INSTRUMENTS 5.1 Give FIVE reasons why we should test electrical appliances. (5) 5.2 List any TWO areas where a potential hazard can cause harm at the work place. (2) 5.3 ifferentiate between digital and analogue meters in a table format. (6) 5.4 State in TWO points what happens if you don't look after your instruments. (2) [15] opyright reserved

9 ( ) -9- N800(E)(M17)V QUESTION 6: SOLERING TEHNIQUES 6.1 State FIVE guidelines to be followed when using the solder sucker and the soldering iron. (5) 6.2 List FIVE steps to be followed when checking quality on the joint after soldering. (5) QUESTION 7: SI ELETRONI IRUITS 7.1 escribe FOUR methods you will use to identify and repair faults. (4) 7.2 raw a flow chart to explain how a sequence of events is planned and instructions interpreted. (6) QUESTION 8: PRINIPLES OF IGITL LOGI 8.1 raw the symbol of an OR gate and write down it's oolean function when the inputs are and and the output is X. (4) 8.2 raw the logic diagram below and complete the truth table that is given below. E F opyright reserved (6)

10 ( ) -10- N800(E)(M17)V QUESTION 9: SI PROGRMMLE LOGI ONTROLLERS (PL) 9.1 riefly explain how a mode switch can be operated. (4) 9.2 riefly explain FOUR precautionary measures you need to take when working with computers. (4) 9.3 Give TWO examples of the field devices you know. (2) QUESTION 10: SI ONEPTS OF TELEOMMUNITIONS 10.1 Explain Network Management in your own words. (2) 10.2 Name FOUR ways that can be used to connect WNs together. (4) 10.3 riefly explain, in your own words, what are the workhorses used by the internet. (2) 10.4 Give TWO main kinds of data networks. (2) TOTL SETION : 100 GRN TOTL: 150 opyright reserved

NATIONAL CERTIFICATE (VOCATIONAL) ELECTRONICS NQF LEVEL 2 NOVEMBER 2009

NATIONAL CERTIFICATE (VOCATIONAL) ELECTRONICS NQF LEVEL 2 NOVEMBER 2009 NTIONL ERTIFITE (VOTIONL) ELETRONIS NQF LEVEL 2 NOVEMER 2009 (10041012) 25 November (X-Paper) 09:00 12:00 Non-programmable calculators may be used. This question paper consists of 9 pages. opyright reserved