WorksheetsETOCA 4
Total questions: 32
Worksheet time: 16mins
What does it mean when an almost full voltage was measured across the terminals 3 and 4 of an actuated Start button on a WYE-DELTA control circuit?
Start button is shorted
Start button is open
Stop button is open
Stop button is shorted
A live conductor carrying high levels of current that is fitted with a current transformer but has no panel ammeter connected can lead to:
significant increase in the live conductor’s current flow
damage in current transformer insulation
significant decrease in the live conductor’s current flow
damage in the load supplied by the live conductor
What is a measuring instrument that is used to measure voltage without actually making any connection in the wire being measured?
Insulation meter
contact type voltage detector
Multimeter
Non-contact type voltage detector
In order to avoid having the wrong rotation of the 3-phase electric motor in the cargo-hold, what instrument needs to be used before connecting the electric motor to the power supply?
frequency meter
oscilloscope
Phase sequence detector
synchroscope
Which of the following electrical testing procedures is not suitable in determining continuity of a control circuit while the circuit is still energized?
resistance test
Current testing
Voltage testing
Frequency testing
Which one of the following current paths for an electric shock is considered the most dangerous to the human body?
From hand to hand, across the chest
From one hand to the ground
From both hands to the ground
From one foot across to the other foot
Which one of these is the main purpose of electrical cable insulation?
To prevent current from flowing anywhere, other than through the conductors
To prevent heat loss to the area around the cable
To protect the conductors from mechanical damage
To protect the conductors in the event of a fire
When using a soldering iron, it's important to:
Heat the iron on a high setting regardless of the task.
Use flux to clean the joint and improve the solder flow.
Cool the soldered joint with water immediately.
Hold the soldering iron with the metal element.
Which tool is used to strip insulation from electrical wires?
Wire strippers
Pliers
Screw drivers
Hammer
Which of the following is the most important safety precaution when working with electricity?
Wearing insulated gloves
Ensuring power is OFF
Using the correct tools
All of the above
Before working on any electrical circuit, you should always:
Turn off the power at the main panel.
Test the circuit to ensure it is de-energized.
Inform others that you will be working on the circuit.
All of the above
When drilling through walls for electrical wiring, it's crucial to:
know the location of existing pipes and wires.
Use the smallest drill bit possible.
Drill at a sharp angle
Ignore any building codes
Which of the following is NOT a primary goal of a planned maintenance system?
minimizing downtime
reducing maintenance costs
maximizing equipment lifespan
eliminating all unplanned breakdowns
A transformer rated at 22 kVA, 440/220 Volts, 60 Hz, is used to step down the voltage to a lighting system. The low-tension voltage is to be kept constant at 220 Volts. What load impedance connected to the lowtension side will cause the transformer to be fully loaded??
0.22 Ω
2.2 Ω
22 Ω
220 Ω
What should be the healthy continuity resistance of a 250 V, 2,5 kW, 10 A heating element, when checked near to its rated operating temperature?
20 Ω
25 Ω
50 Ω
100 Ω
Which one of the following describes how the inductance of an electrical coil can be increased?
Wind the conductor around a core that can be magnetized
Use smaller diameter conductor
Wind the conductor around a long plastic core
Increase the voltage applied to the inductor
With regard to a star connected electrical machine, which one of the following statements is true?
The phase current is the same as the line current
The phase voltage is the same as the line voltage
The phase current is smaller than the line current
The phase voltage is larger than the line voltage
A triac is used to provide temperature control of an oven. The galley complains that the oven only reaches approximately 50% of the demanded temperature. Which of the following is likely cause?
The triac has completely failed.
The voltage supply to the oven controller is reduced by about 50%.
One of the main switching elements in the triac has failed.
Connection between the demand knob and the triac gate terminal has gone open circuit.
What is the maximum current that a 15 V, 3-watt Zener diode can handle without damage?
20 A
2,0 A
0.2 A
0.02 A
If you are going to use diode in a circuit, which of the following is not a possible function of a semiconductor diode in electronic circuits?
Signal regulator
Signal indicator
Signal detector
Signal filter
A 250 V contactor has been fitted to a 220 V supply. Which of the following symptoms might be observed?
Contactor overheating.
The contractor won’t operate.
Contactor chattering/vibrating.
Contactor constantly on.
The motor is protected by a thermal overcurrent relay. After tripping on overload it will not be possible to reset the overcurrent relay immediately because the_________________________.
starter isolator automatically applies an interlock
oil dashpot must be reset
line contactor spring must be reset
bimetallic strips need time to cool down
Continuity testing of a delta connected three phase induction motor yields the following results; U – V = 8.9 ohms, V – W = 8.9 ohms, W – U = 17.8 ohms. Which of the following is the likely condition?
Partial fault between W and U.
Short circuit winding between W and U.
Short circuit between V and Earth.
Open circuit winding between W and U.
A galley hot plate uses a Nichrome / Magnesium Oxide heating element and is to be tested before being put into service for the first time. An insulation resistance test yields a reading of 0.5 MΩ. Which action should be taken?
Discard the element.
Apply reduced voltage to the element for a few minutes. Then retest and if ok put into service.
Wash the element in a degreasing agent. Then retest and if ok put ino service.
Put the element into service.
Which of the following describes the starting current of an electrical motor?
Starting current = Full load current
Starting current > Full load current
Starting current = Locked rotor current
Starting current > Locked rotor current
A welding cable has a resistance of 200 milli-ohms. It supplies a 200 A load over a distance of 100 meters. What is the voltage drop along its length?
400 milli-Volts
4.0 Volts
40 Volts
400 Volts
When starting 3-phase induction motors, which of the following starting methods will immediately apply rated voltage to the machine?
Direct on Line
Auto-transformer
Star Delta
Soft starter
Which of the following does not describe the correct function of protection relay?
Close the contacts when the actuating quantity reaches a certain predetermined value.
Limit arcing current during the operation of the circuit breaker.
Does not trip or interrupt the circuit breaker.
Protect the lines from any stray voltages.
A transformer with two windings, N (1) = 2 000 and N (2) = 1 000 turns, on a common magnetic circuit. Assume that there are no energy losses in the transformer itself. Calculate the output voltage V (2) when the input voltage is V (1) = 100 Volt.
V (2) = 10 V
V (2) = 20 V
V (2) = 50 V
V (2) = 200 V
Which of the following is NOT a typical component of an electro-pneumatic system's safety lockout procedure?
Locking out the main electrical disconnect
Bleeding off any residual air pressure.
Disconnecting all pneumatic tubing.
Applying a lockout tag to the pneumatic and electrical isolation points.
During troubleshooting, if you suspect a problem with a solenoid valve, what is a safe way to test it?
Directly apply voltage to the solenoid terminals with a jumper wire.
Use a multimeter to check for continuity and voltage at the solenoid coil.
Bypass the solenoid valve with a manual valve.
All the above
In a hydraulic system, a slight reduction of oil flow will cause the torque to __________ in a hydraulic motor.
become erratic
be reduced
be increased
remain the same
