NATIONAL CERTIFICATE (VOCATIONAL) NQF LEVEL 2 SUPPLEMENTARY EXAMINATION

Transcription

1 MARKING GUIDELINE NATIONAL CERTIFICATE (VOCATIONAL) NQF LEVEL 2 SUPPLEMENTARY EXAMINATION 2010 This marking guideline consists of 8 pages.

2 MARKING GUIDELINE -2- NC770(E)(F19)V SECTION A QUESTION 1: COMPONENTS 1.1 W + W X - X J J I I H H G G F F E D C B A E D C B A Y - Y Z + Z Figure 1 Top View of a Breadboard The Top view of a breadboard indicates that: (for fully labelled diagram only) Between each section there is no connection The holes are placed in groups of five both horizontally (1 5) as well as vertically (A E and F J) The groups of holes are connected by copper strips, underneath the breadboard The top and bottom rows of holes (WW, XX, YY, ZZ) are used for power supply Positive (+) is connected to the red rows (WW and ZZ), while negative (-) is connected to the blue rows (XX and YY) To make connections you only need to inset the uninsulated ends of the wires into a set of holes. (for explanatory notes) [ANY FIVE] (1 10)

3 MARKING GUIDELINE -3- NC770(E)(F19)V 1.2 Elements of an analogue multimeter when measuring voltage Pointer needle Range of Functions switch Test leads or probes Ohms/volts jack or socket Common jack or socket DC & AC volts scale DC volts range AC volts range Leads: Black = negative Red = positive [ANY FIVE] (1 5) (5) 1.3 Factors that influence resistance: The length of the conductor The cross-sectional area of the conductor The resistivity of the conductor material The temperature at which the conductor material is operating. (1 4) (4) 1.4 Violet 7 Orange 3 Gold 10-1 OR (x 0,1) Yellow ±4 % Therefore, L = 7,3 µh ±4% TABLE 1 (1 5) (5) 1.5 Leads of a transistor Base Collector Emitter (1 3) (3) Operational Amplifier types T05 casing, and The 8-pin Op Amp in-line The most commonly available type is the 8-pin version. (1 3) (3) [30]

4 MARKING GUIDELINE -4- NC770(E)(F19)V QUESTION 2: CIRCUIT DIAGRAMS 2.1 Factors that influence inductance Material used for the core Number of turns in the coil Cross-section area of each turn Length of the coil (1 4) (4) 2.2 Parallel-series network of inductors L 1 = 5 mh L 3 = 6 mh L 2 = 20 mh FUGURE 2 L P = (L 1 x L 2 ) (L 1 + L 2 ) = (5 x 20) (5 + 20) = = 4 mh Therefore L T = L P + L 3 = = 10 mh (1 4) (4) 2.3 Parallel network of capacitors C 1 = 6 µf C 2 = 9 µf C 3 = 5 µf FIGURE 3 (1 3) (3) 2.4 C P = C 1 + C 2 + C 3 = = 20 µf ( 1 2) (2)

5 MARKING GUIDELINE -5- NC770(E)(F19)V 2.5 A resistor is a passive component or device that offers a specific amount of electrical opposition to the flow of current when connected in the circuit (1 2) (3) [15] SECTION B QUESTION 3: BINARY THEORY AND FLIP-FLOPS TABLE = = (1 5) (5) 3.2 Decimal input MSD BCD Output 1 1 LSD FIGURE 4: Decoder from Decimal to 8421 BCD code (1 10) (10)

6 MARKING GUIDELINE -6- NC770(E)(F19)V Check (20) (14) (6) (6) TABLE 3 (1 5) Answer = 6 10 SD D Q CL Q RD FIGURE 5: IEC Symbol of a D-type Flip-Flop (1 6) (6) D Q Q TABLE 4 (1 3) 3.5 The Modulus of a counter is the total number of states through which that counter can progress. (1 1) (1) [30]

7 MARKING GUIDELINE -7- NC770(E)(F19)V QUESTION 4: BASIC COMPUTER COMPONENTS 4.1 Computer components inside a tower case Power supply unit (PSU) Hard drive Motherboard Media drives, e.g. CD, DVD. USB flash, floppy, etc. (1 4) (4) 4.2 Computer ports Parallel Serial Audio VGA USB PS/2 RJ45 LAN, etc. [ANY TWO] (1 2) (2) 4.3 Types of CDs CD ROM (Compact Disk Read Only Memory) CD-R (Compact Disk Recordable) CD RW (Compact Disk Read/Write) (1 3) 4.4 Non-volatile memory ROM Flash memory Hard drive Optical disk Compact disk, etc. [ANY THREE] (1 3) (3) 4.5 Features of a flash memory It is durable It is quickly erasable It is small It is manageable It is easy to use It is a re-writable memory It is non-volatile It does not make use of a drive (USB) It has a relatively large storage capacity (Upwards of several Giga Bytes) [ANY THREE] (1 3) (3) [15] TOTAL SECTION B: 50

8 MARKING GUIDELINE -8- NC770(E)(F19)V SECTION C QUESTION 5: TRANSDUCERS USED IN PROCESS CONTROL T F F T T (1 5) (5) 5.2 Factors affective the capacity of a capacitive transducer Area of the plates Distance between the plates Insulation material between the plates. (1 3) (3) 5.3 Applications of an LVDT Measuring mechanical displacement Measuring pressure: deflection of a diaphragm. (1 2) (2) [10] TOTAL SECTION B: 10 GRAND TOTAL: 100