Electrical Technology Grade 12 P1 Gauteng June 2025 Memo

Eng JUNE EXAMINATION GRADE 12 2025 MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS 15 pages

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 INSTRUCTIONS TO MARKERS 1. All questions with multiple answers imply that any relevant, acceptable, and correct answer should be considered. 2. Calculations: 2.1 All calculations must show the formulae. 2.2 Substitution of values must be done correctly. 2.3 All answers MUST contain the correct unit to be considered. 2.4 Alternative methods must be considered, provided that the correct answer is obtained. 2.5 Where an incorrect answer could be carried over to the next step, the first answer will be deemed incorrect. However, should the incorrect answer be carried over correctly, the marker has to recalculate the values, using the incorrect answer from the first calculation. If correctly used, the candidate should receive the full marks for subsequent calculations. 3. These marking guidelines are only a guide with model answers. Alternative interpretations must be considered and marked on merit. However, this principle should be applied consistently throughout the marking session. 4. NB: Due to a printing error on the answer sheet, Question 5.4.4 must not be marked. Draw a line through this question when marking, and mark the whole question paper out of 197 marks. Use the conversion table on the next page to then convert the mark out of 197 back to a mark out of 200 for entry onto SASAMS. Show both sets of marks on the front of the learners answer script. 2

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 3

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 QUESTION 1: MULTIPLE-CHOICE QUESTIONS 1.1 D✓ (1) 1.2 D✓ (1) 1.3 B✓ (1) 1.4 C✓ (1) 1.5 B✓ (1) 1.6 C✓ (1) 1.7 A✓ (1) 1.8 D✓ (1) 1.9 C✓ (1) 1.10 B ✓ (1) 1.11 C ✓ (1) 1.12 A ✓ (1) 1.13 B ✓ (1) 1.14 A ✓ (1) 1.15 D ✓ (1) [15] 1.1 A B C X 1.2 A B C X 1.3 A X C D 1.4 A B X D 1.5 A X C D 1.6 A B X D 1.7 X B C D 1.8 A B C X 1.9 A B X D 1.10 A X C D 1.11 A B X D 1.12 X B C D 1.13 A X C D 1.14 X B C D 1.15 A B C X 4

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 QUESTION 2: OCCUPATIONAL HEALTH AND SAFETY 2.1 2.1.1 Any person who employs (provides work) for any other person, ✓ and remunerates (pays) that person. ✓ (2) 2.1.2 The probability that injury or damage will occur. ✓ (1) 2.2 • A dangerous substance that was spilled. ✓ • The uncontrolled release of any substance under pressure. • Flying, or falling objects due to machine failure. • Machinery running out of control. (1) 2.3 The person may place themselves and other people in danger while operating the machinery. ✓ The person may also cause damage to the machinery. ✓ (2) 2.4 • Move in an orderly manner. ✓ • Follow the evacuation route as displayed in your workshop. ✓ • Move to the designated assembly point in a calm and orderly manner. (Any correct and relevant answer) (2) 2.5 • Quantitative risk analysis ✓ • Qualitative risk analysis ✓ (2) [10] QUESTION 3: RLC CIRCUITS 3.1 The shift in phase between the supply voltage and current ✓ as a result of the resistances and reactance within a circuit. ✓ (2) 3.2 Inductive. ✓ The current waveform lags ✓ the voltage waveform by 90°. ✓ OR Inductive. The voltage waveform leads the current waveform by 90°. (3) 3.3 • The frequency. ✓ • The capacitance of the capacitor. ✓ (2) 3.4 The resistance will remain unchanged, ✓ while the current and voltage will still remain in phase. ✓ (2) 3.5 • Wattles voltage dividers ✓ • Timing circuits ✓ • Filter circuits ✓ • Oscillating circuits ✓ • Radio-tuning circuits ✓ (5) 5

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 3.6 3.6.1 Z = √𝑅 2 + (XL − Xc)² ✓ = √12² + (24 − 18)² ✓ = 13,42 Ω ✓ (3) 3.6.2 𝐼𝑇 = 𝑉𝑇 ✓ 𝑍 150 = 13,42 ✓ = 11,18 A ✓ (3) 3.6.3 ∅ = 𝐶0𝑆-1 𝑍 𝑅 ✓ 12 Ω = 𝐶0𝑆-1 13,42Ω ✓ = 26,60° ✓ (3) 3.6.4 Inductive ✓ (XL is greater than XC) (1) 3.6.5 When the impedance of the circuit increases, the phase angle will also increase ✓ therefore resulting in a decreasing power factor value. ✓ (2) 3.7 The voltages appearing across both the inductor and capacitor can be greater than the supply voltage when the circuit is near resonance, ✓ and because both their voltages are out of phase with one another ✓ a cancelling (subtracting) effect will take place to result in a combined voltage lower than the supply. ✓ (3) 3.8 3.8.1 𝐼𝑇 = √𝐼𝑅 2 + (𝐼𝐿 − 𝐼𝐶 )2 ✓ = √62 + (4 − 3)2 ✓ = 6,08 A ✓ (3) 6

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 3.8.2 𝐼𝐶 ✓ ✓ 𝐼𝑅 ✓ Ø 𝑉𝑇 ✓ 𝐼𝑋 ✓ 𝐼𝑇 𝐼𝐿 ✓ Direction of rotation compulsory = 1 mark Voltage reference compulsory = 1 mark Any four other correct labels = 4 marks (6) 3.8.3 The voltages across the components in a parallel circuit are the same, ✓ therefore voltage is used as a reference. (1) 3.8.4 The circuit is inductive ✓ because the inductive current is greater than the capacitive current. ✓ (2) 3.8.5 • XL = XC. ✓ • IT is at a maximum. ✓ • Z is at a minimum. ✓ • Z = R. ✓ • Phase angle is 0° (4) 3.9 • The value of the series resistor ✓ • The LC ratio ✓ (2) 3.10 The Q-factor will be halved ✓ because the Q-factor is inversely proportional to the resistance of the circuit. ✓ Doubling of the inductance and capacitance values will have no effect on their ratio in the calculation. ✓ (3) 3.11 A narrow bandwidth. ✓ (1) 3.12 3.12.1 𝑋𝐿 = 2𝜋 𝑓 𝐿 ✓ = 2π × 150 × 1,06 ✓ = 999,03 Ω ✓ (3) 7

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 3.12.2 𝑋 Q = 𝑅𝐿 ✓ 999,03 = ✓ 10 = 99,90 ✓ (3) 3.12.3 𝑉𝐿 = 𝑄 × 𝑉𝑇 ✓ = 99,9 × 6 ✓ = 599,4 V ✓ (3) [60] QUESTION 4: SEMICONDUCTOR DEVICES 4.1 Field Effect Transistor ✓ (1) 4.2 The FET makes use of only one charge carrier to control the flow of current, ✓ either electrons or holes, but not both. ✓ (2) 4.3 A – Drain ✓ B – Gate ✓ C – Source ✓ D – Channel ✓ (4) 4.4 4.4.1 N-Channel ✓ Enhancement mode MOSFET. ✓ (2) 4.4.2 R1 and R2 are biasing resistors ✓ which set its operating point to the centre (linear region) of the transfer characteristic curve. ✓ (2) 4.4.3 It will cause the internal conductive channel of the MOSFET to disappear ✓ cutting the current flow and ✓ switching the output off. ✓ (3) 4.5 • When the B1 and B2 terminals of a UJT are connected to a supply voltage, a voltage drop will develop across its length. ✓ • This voltage drop will be divided in two between B1 and the Emitter, and B2 and the Emitter. ✓ • When a separate voltage is applied to the Emitter that is lower than the potential dividers voltage (VX), the UJT will be switched off. ✓ • When the separately applied voltage to the Emitter is higher than the potential dividers voltage (VX), the UJT will switch on and conduct. ✓ (4) 8

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 4.6 4.6.1 Darlington pair. ✓ (1) 4.6.2 Each transistor requires 0,7V to switch on, ✓ therefore 1,4V needs to be present across R2 for them to both switch on. ✓ (2) 4.6.3 It provides a high current gain to the circuit. ✓ It improves (increases) the input impedance of the circuit. ✓ (2) 4.7 • Infinite open loop gain ✓ • Infinite input impedance ✓ • Zero output impedance ✓ • Infinite bandwidth • Infinite common mode rejection ratio (Any 3 correct answers) (3) 4.8 4.8.1 Inverting operational amplifier circuit. ✓ (1) 4.8.2 The purpose of the feedback resistor is to take a part of the output signal back to the input, ✓ and thereby control (reduce) the gain of the circuit to the required level. ✓ (2) 4.8.3 Op-amps are seldom used in an open loop mode because of their very high gain ✓ which causes it to be unstable. ✓ (2) 4.8.4 𝑅 𝐴𝑉 = − 𝑅 𝐹 ✓ 𝐼𝑁 3.3 ×103 = − 1,2×103 ✓ = − 2,75 ✓ (3) 4.8.5 𝑉𝐼𝑁 = 𝑉𝑂𝑈𝑇 ✓ 𝐴𝑉 825×10−3 = ✓ −2,75 = −300 mV ✓ (3) 4.9 • Turning a light ON or OFF after a period of time. ✓ • Pulse oscillation and wave generation. ✓ • Creating a flashing warning light. • Digital logic probes. • Producing musical notes of specific frequencies. • Temperature measurement. • Controlling the positioning of servo devices. (Any 2 correct answers) (2) 9

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 4.10 • It is an active low trigger. ✓ • When the voltage on pin 2 is less than1/3 of the supply, the output will increase.✓ • When the voltage on pin 2 is higher than 2/3 of the supply, the output will decrease. ✓ (3) 4.11 The SR flip-flop stores ✓ the incoming information temporarily, ✓ until new information is received. ✓ (3) [45] QUESTION 5: SWITCHING CIRCUITS 5.1 5.1.1 Free running ✓ multivibrator (1) 5.1.2 Zero ✓ (1) 5.2 5.2.1 To prevent the IC from resetting itself ✓ when the S1 (SET) is pressed and then released, ✓ therefore keeping the output HIGH. ✓ (3) 5.2.2 Pull-up ✓ (1) 5.2.3 Without pull-up resistor R2 connected to the supply, the voltage on Pin 4 will continuously vary (float) ✓ between 0 V and 6 V.✓ (2) 5.2.4 VCC 0V VCC 0V ✓ ✓ ✓Orientation 0V NOTE: No mark awarded for orientation if the waveform is inverted. (3) 5.3 5.3.1 C2 ✓ and R3 ✓ (2) 5.3.2 0 V✓ (1) 5.3.3 The moment a positive pulse is applied to the inverting input, the output changes from positive saturation (+9 V) ✓ to negative saturation (-9 V) ✓ for a certain duration of time. ✓ (3) 10

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 5.3.4 VIN ✓ ✓ +9 V ✓ VOUT Orientation ✓ -9 V VB NOTE: No mark awarded for orientation if the waveform is inverted. (4) 5.4 5.4.1 The LED will be ON. ✓ (1) 5.4.2 ±8 V ✓ (⅔ Vcc) (1) 5.4.3 The duration ✓ of the train of on-off pulses during switch bounce are shorter than the charging cycle of the capacitor. ✓ Only when the capacitor has charged to point Y will the circuit change state. (2) 11

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 5.4.4 Bounce Input t VC1 t Y ✓ ✓ Output Orientation ✓ t NOTE: No mark awarded for orientation if the waveform is inverted. (3) 5.5 5.5.1 This is a closed loop ✓ operational amplifier circuit because R2 creates a positive feedback loop from the output to the non-inverting input. ✓ (2) 5.5.2 The trigger voltage levels can be adjusted by changing the value of either R1 ✓or R2. ✓ (2) 12

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 5.5.3 ✓ ✓ +V ✓ -V Orientation ✓ NOTE: No mark awarded for orientation if the waveform is inverted. (4) 5.6 5.6.1 Comparator circuit. ✓ (1) 5.6.2 • Voltage divider resistors R1 and R2 set up the reference voltage (VREF). ✓ • The Op-amp comparator compares the input voltage (VIN) to the reference voltage (VREF). ✓ • When the input voltage on the inverting input is lower than the reference voltage, ✓ the Op-amp is driven to positive saturation. ✓ • When the input on voltage is higher than the reference voltage, ✓ the Op-amp is driven into negative saturation. ✓ (6) 5.7 5.7.1 Summing amplifier circuit. ✓ (1) 5.7.2 Negative feedback. ✓ Controlling the gain of the amplifier. ✓ (2) 13

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 5.7.3 𝑅 𝑅 𝑅 𝑉𝑂𝑈𝑇 = − ( 𝑉1 𝑅1𝐹 + 𝑉2 𝑅2𝐹 + 𝑉3 𝑅3𝐹) ✓ 80000 80000 80000 = − ( 0,5 10 000 + 0,6 10 000 + 0,15 10 000) ✓ = −10 𝑉 ✓ (3) 5.7.4 When the RF increases the gain of the amplifier also increases. ✓ (1) 5.7.5 𝑅 𝑅 𝑅 𝑉𝑂𝑈𝑇 = − ( 𝑉1 𝑅1𝐹 + 𝑉2 𝑅2𝐹 + 𝑉3 𝑅3𝐹) ( Rin = R1 = R2 = R3 ) ✓ 𝑅 𝑅 𝑅 𝑉𝑂𝑈𝑇 = − ( 𝑉1 𝑅 𝐹 + 𝑉2 𝑅 𝐹 + 𝑉3 𝑅 𝐹 ) 𝑖𝑛 𝑖𝑛 𝑖𝑛 𝑉𝑂𝑈𝑇 × 𝑅𝑖𝑛 ∴ 𝑅𝐹 = ✓ (𝑉1+𝑉2+𝑉3) 12 × 10000 = (0,5+0,6+0,15) ✓ = 96 𝑘Ω ✓ (4) 5.7.6 This can be achieved by setting the supply voltage to a higher value, i.e. higher than 12 V ✓ or by decreasing the input voltage of each input respectively.✓ (2) 5.8 5.8.1 ✓ ✓ ✓ VIN ✓ VOUT ✓ ✓ 0V (6) 5.8.2 • Improved input and output impedances. ✓ • Boosts the output gain. ✓ • Compensates for losses. • Added stability to the circuit. (Any 2 correct answers) (2) 14

MARKING GUIDELINES ELECTRICAL TECHNOLOGY: ELECTRONICS GR12 0625 5.9 5.9.1 The output of an integrator is proportional to the amplitude ✓ and period ✓ of the input signal. (2) 5.9.2 Input t Output ✓ ✓ t (2) 5.9.3 Input t Output ✓ ✓ t (2) [70] TOTAL: 200 15