QUESTION 1: MULTIPLE-CHOICE QUESTIONS
Various options are provided as possible answers to the following questions - NSC Electrical Technology Power Systems - Question 1 - 2021 - Paper 1
Question 1
QUESTION 1: MULTIPLE-CHOICE QUESTIONS
Various options are provided as possible answers to the following questions. Choose the answer and write only the letter (A–D)... show full transcript
Worked Solution & Example Answer:QUESTION 1: MULTIPLE-CHOICE QUESTIONS
Various options are provided as possible answers to the following questions - NSC Electrical Technology Power Systems - Question 1 - 2021 - Paper 1
Step 1
1.1 Choose the correct example of an unsafe condition that is likely to cause damage to property or an injury:
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Answer
The correct answer is A: Running in the workshop. This action poses a significant risk of injury resulting from slips, trips or falls in a potentially hazardous environment.
Step 2
1.2 An RLC series circuit is predominantly inductive when …
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Answer
The correct answer is B: XL>XC. This indicates that the inductive reactance is greater than the capacitive reactance, leading to a predominantly inductive circuit.
Step 3
1.3 The phase angle of a predominantly capacitive RLC series circuit is …
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Answer
The correct answer is A: leading. In a capacitive circuit, the current leads the voltage.
Step 4
1.4 The … of a resonant circuit is the measure of how well it responds to a range of frequencies.
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Answer
The correct answer is C: resonant frequency. This is the frequency at which the circuit naturally oscillates with maximum amplitude.
Step 5
1.5 The standard international phase sequence for a three-phase system is …
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Answer
The correct answer is A: red, yellow, blue. This is the commonly accepted color code for three-phase systems.
Step 6
1.6 The phase angle between any two phases of a balanced three-phase system is …
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Answer
The correct answer is D: 120 degrees. This phase angle indicates equal spacing between the phases in the system.
Step 7
1.7 A measuring instrument used to measure electrical energy is …
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Answer
The correct answer is B: kWh meter. This instrument specifically measures the amount of electrical energy consumed over time.
Step 8
1.8 A step-up transformer is used to …
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Answer
The correct answer is D: increase the voltage. Step-up transformers convert low voltage to high voltage.
Step 9
1.9 In three-phase transformers, the transfer of electrical energy from the primary winding to the secondary winding takes place by means of …
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Answer
The correct answer is A: mutual induction. This is the principle that allows energy transfer between coils in the transformer.
Step 10
1.10 Which ONE of the following relates to a mechanical inspection of a three-phase motor?
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Answer
The correct answer is A: Insulation-resistance test between the windings and earth. This test checks for insulation integrity to prevent short circuits.
Step 11
1.11 The function of an overload relay in a motor starter control circuit is to …
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Answer
The correct answer is B: deactivate the control circuit and to isolate the power circuit when excessive current flows through the motor. This protects the motor from damage.
Step 12
1.12 The speed of rotation of the magnetic field in the stator windings is called … speed.
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Answer
The correct answer is C: synchronous. This refers to the speed at which the magnetic field rotates in a synchronous motor.
Step 13
1.13 The chronological order of operation for the scan cycle of a PLC is …
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Answer
The answer should indicate the steps of scanning inputs, updating the process, outputting results, and cyclically repeating these actions.
