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WorksheetsUnit 15 - ELT 503 (Practice CBT)
Total questions: 10
Worksheet time: 50mins
What is the first action to be taken when a thermal overload trips an induction motor?
Short circuit the thermal trip
Disconnect the thermal trip
Replace the thermal trip
Reset the thermal trip
Which is an example of incorrect polarity in electrical installations?
Live and neutral conductors interchanged at a socket-outlet
Live conductor connected to the wrong phase conductor
Earth conductor not connected at a socket-outlet
Open-circuit neutral conductor
What is the most likely cause of a three-phase motor failing to develop enough torque to drive its load?
Reverse phasing
Drop in frequency.
Rise in frequency
Single phasing.
What is the operating resistance of a single-phase 230 V heating element rated at 3 kW?
7.7 Ω
13.1 Ω
17.6 Ω
25.5 Ω
What is the cause of an open circuit when testing the continuity of the line conductor in a lighting circuit?
Switch is open.
Neutral and line are interchanged.
Neutral is open circuit
Conductor insulation is failing.
What is the cause of a low resistance between line and earth on a single-phase motor?
Partial short-circuit winding to frame
Short-circuit line to neutral
Partial open-circuit
Short-circuited turns in a winding
What is the cause of a hot bearing on a three-phase motor?
Lack of lubrication.
Overheated windings.
Poor ventilation.
Single phasing.
Which test connections are used when testing a single phase appliance for insulation?
L & N to E
E to N
N & E to L
L to N
What condition will cause a lamp controlled by a photoelectric cell to turn on?
movement within its range
increase the light level
change in temperature
decrease in light level
What component is required to control the starting capacitor in a single phase induction motor?
shunt coil
thermal trip
discharge resistor
centrifugal switch
