ETC ETC Electrical Systems & Instrumentation 1 — Questions and Answers
Question 1: What does the term 'voltage drop' refer to in an electrical circuit?
- Reduction in voltage across a component due to resistance (Correct answer)
- Increase in current through a resistor
- Loss of frequency in an AC circuit
- Drop in power factor below unity
Correct answer: Reduction in voltage across a component due to resistance
Voltage drop is the reduction in electrical potential across a passive element caused by resistance in the circuit.
Question 2: Which instrument is used to measure electrical resistance in a circuit?
- Voltmeter
- Ammeter
- Ohmmeter (Correct answer)
- Wattmeter
Correct answer: Ohmmeter
An ohmmeter is specifically designed to measure electrical resistance in ohms.
Question 3: What is the purpose of a circuit breaker in an electrical panel?
- To increase voltage supply
- To protect wiring from overcurrent by interrupting the circuit (Correct answer)
- To reduce power factor
- To step up transformer output
Correct answer: To protect wiring from overcurrent by interrupting the circuit
A circuit breaker automatically interrupts current flow when it exceeds safe levels, protecting wiring and equipment from damage.
Question 4: In a three-phase power system, what is the phase angle difference between each phase?
- 90 degrees
- 45 degrees
- 120 degrees (Correct answer)
- 180 degrees
Correct answer: 120 degrees
In a balanced three-phase system, each phase is separated by 120 degrees to evenly distribute power.
Question 5: Which type of sensor converts physical displacement into an electrical signal?
- Thermocouple
- LVDT (Linear Variable Differential Transformer) (Correct answer)
- Pitot tube
- Bourdon gauge
Correct answer: LVDT (Linear Variable Differential Transformer)
An LVDT converts linear mechanical displacement into a proportional electrical voltage output.
Question 6: What does a 4-20 mA signal represent in industrial instrumentation?
- A digital binary signal for on/off control
- A standard analog current loop used to transmit process variable data (Correct answer)
- A high-voltage DC signal for motor drives
- A frequency modulated signal for PLCs
Correct answer: A standard analog current loop used to transmit process variable data
The 4-20 mA current loop is the industrial standard analog signal where 4 mA represents the minimum range and 20 mA the maximum.
ETC ETC Electrical Systems & Instrumentation 1
What does the term 'voltage drop' refer to in an electrical circuit?