NATIONAL CERTIFICATE (VOCATIONAL) ELECTRONICS NQF LEVEL 2 NOVEMBER 2009

Transcription

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

2 ( ) -2- N800(E)(N25)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 LL the logic gates. Write neatly and legibly. opyright reserved

3 ( ) -3- N800(E)(N25)V SETION QUESTION Various options are given as possible answers to the following questions. hoose the answer and write only the letter ( ) next to the question number ( ) in the NSWER OOK In a generator, the two ends of this device are attached to different halves of one split ring which rotates with this device: lternator oil Nuclear power Wind power (1) It can be used to block high frequency current, while allowing low frequency and direct current to pass: Polarised capacitor Photo diode Inductor Impedance (1) It could affect the heart, major arteries or veins could tear, leading to internal bleeding: Electric charges Lightning Falling from step ladder Electric shock (1) It measures repetitions per unit of time, usually per second of a complete electromagnetic waveform: Frequency meter Tong tester Wattmeter Voltmeter (1) Inspecting the work area involves applying the soldering iron tip to melt solder joint. using expensive irons with thermostat. choosing the correct heating apparatus, soldering iron and cleaning agents. oxidation. (1) opyright reserved

4 ( ) -4- N800(E)(N25)V One of the important steps to follow when checking the circuit visually for faults: The circuit board be clean ircuit design Layout Schematic diagram (1) The output of this gate will be logic 0, if any of the inputs is logic 1: EXOR NN OR NOR (1) Selecting the correct addressing modes is done at a certain stage so that the PL knows what is connected and where to find it: onnecting to the back plane Programming Hardware assembling Output peripherals (1) The microphone uses this device to convert sound waves into electrical signals: Multiplexing M modulation Piezoelectric rosstalk (1) modern fax machine does not have these devices and is a lot faster: Rotating drums PSTNs ata networks PX(s) (1) opyright reserved

5 ( ) -5- N800(E)(N25)V 1.2 Indicate whether the following statements are TRUE or FLSE. hoose the answer and write only 'true' or 'false' next to the question number ( ) in the NSWER OOK Electrons flow from the regions of positive charge to the regions of negative charge. (1) The effect of low temperature on a P-N junction, the valence band is completely full, making the material an insulator. (1) When treating a victim for burns after electrical shock, apply grease or oil on the burned area and cover it with a clean bandage. (1) Ohm meters are designed to measure resistance in ohms and are not meant to become part of the circuit. (1) It is important to dispose of the waste materials correctly as you know it makes a good fertiliser and improves the environment. (1) conductive path disallows the electricity to flow through, this is usually a metal wire. (1) Subtracting a positive number is the same as adding a negative number of the same value. (1) field device can be a circuit board or assembly that cannot be removed quickly and easily from a PL. (1) data network is a digital computer network that is used to send documents but doesn't include video and audio information. (1) The servers and clients talk to each other through a number of languages called protocols. (1) opyright reserved

6 ( ) -6- N800(E)(N25)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 the NSWER OOK. OLUMN OLUMN Even though these fuels are useful, by using them we cause pollution which damages the environment report hazards The two plates of a capacitor which have opposite charges are separated by a small distance that does not conduct N job card Water taps must be separated from the electronic work bench and there must be an emergency exit E F impedance connection When people work in these conditions they must be aware of them and know how to deal with them in a safe way G H NN diode s the solder begins to melt, it flows around it Information such as the guarantee on the job appears on this document I J K fossil data networks internet The lamp will turn on only when both switches and connected in series are closed L M electrolytic electric shock Two power supplies are connected to the PL from different sources and they are separated by this device N O dielectric veroboard It weakens a reflected signal because a portion of a transmitted signal is reflected back to the transmitting device P Q electrical safety multiplexing It is a network of computers networks that understand the same language for transferring data (10 x 2) (20) opyright reserved

7 ( ) -7- N800(E)(N25)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 The difference in charge produced by the battery is stored in the battery as electrical potential energy is called. (1) n N-type has an excess of free electrons, and a P-type has an excess of holes. (1) We need to protect ourselves against electrical shock by using insulation and. (1) (1) The of a soldering iron is made of copper since copper is a good conductor of heat. (1) helps you to see how the components will all fit together and how to organise the components you will need to build a circuit. (1) The output of a... gate will be logic 0, if any one of the inputs is logic 1. (1) When connecting and disconnecting the device from its host, remember to switch it off before you do this. (1) from one communication device, for example, the telephone, travel through the wires and are picked up at the other end. (1) The main disadvantage of analogue signaling is that the system will probably have. (1) TOTL SETION : 50 QUESTION 2: FUNMENTLS OF ELETRIITY 2.1 Name THREE types of usable energy resources that we can use to produce electricity without polluting the environment. (3) 2.2 With the aid of a sketch and graphical representations, explain power supply consisting of a transformer, full wave rectifier that uses four diodes, capacitor and a load resistor. (7) opyright reserved

8 ( ) -8- N800(E)(N25)V QUESTION 3: SI ELETRONI THEORY N ONEPTS 3.1 onvert 10 nano-farads to pico-farads and to micro-farads. (3) 3.2 escribe FOUR facts on how photo diodes as specialised components are used. (4) 3.3 alculate the total inductance of three inductors with values of 5 mh, 8 mh and 3 mh if they are connected in parallel. (3) QUESTION 4: ELETRIL SFETY STNRS 4.1 List any FIVE important phrases you should remember that are connected to electrical safety in case you work with electricity. (5) 4.2 State any FIVE basic safety tips to avoid electrical accidents. (5) 4.3 Name any FIVE effects that happen when electricity passes through a human body. (5) [15] QUESTION 5: USE N RE OF HN HEL ELETRIL TEST INSTRUMENTS 5.1 escribe any SIX general points to look for when inspecting a test instrument before use. (6) 5.2 State THREE important rules for caring for your test instruments. (3) 5.3 escribe, in a correct sequence, the steps you would follow when removing a battery from your equipment. (6) [15] QUESTION 6: SOLERING TEHNIQUES 6.1 efine the term tinning. (2) 6.2 State the SIX guidelines to be followed when inspecting the work area. (6) 6.3 Name the tool that is used to take off the insulation that covers the conductor. (1) 6.4 What is the cause of oxidation? (1) opyright reserved

9 ( ) -9- N800(E)(N25)V QUESTION 7: SI ELETRONI IRUITS 7.1 With the aid of a schematic diagram, show how a two button buzzer circuit would operate. (5) 7.2 riefly explain how the correct voltage is selected and power is applied when a circuit is tested for faults. (5) QUESTI0N 8: PRINIPLES OF IGITL LOGI 8.1 onvert the following decimal numbers to the binary number system and then do the addition in the binary number system: (8) 8.2 efine an OR gate. (2) QUESTION 9: SI PROGRMMLE LOGI ONTROLLERS (PL) 9.1 Give any FIVE examples where PL's are used. (5) 9.2 State FOUR basic things needed when you create or change a program. (4) 9.3 Give ONE example of an analogue output signal. (1) QUESTION 10: SI ONEPTS OF TELEOMMUNITIONS 10.1 State TWO components of the Simple Network Management Protocol. (2) 10.2 List FOUR signal problems that can occur when sending information over long distances. (4) 10.3 riefly explain what collision avoidance is. (2) 10.4 escribe a PX system. (2) TOTL SETION : GRN TOTL: opyright reserved