#1
Which of the following devices is used to control the flow of electric current in a circuit?
Fuse
Switch
Contactor
Capacitor
#2
What is the primary function of an electrical contactor?
To regulate voltage
To convert AC to DC
To control the starting and stopping of electric motors
To measure current flow
#3
Which of the following statements is true regarding overload relays?
They protect against short circuits
They protect against overvoltage
They protect against overcurrent
They protect against grounding faults
#4
What is the main function of an auxiliary contact in a contactor or relay?
To provide power to the device
To trigger the device
To provide additional switching capabilities
To regulate voltage
#5
What is the primary difference between a normally open (NO) and a normally closed (NC) contact in a relay?
NO contact is open in the resting state, while NC contact is closed
NO contact is closed in the resting state, while NC contact is open
NO contact is used for low-voltage circuits, while NC contact is used for high-voltage circuits
There is no difference between NO and NC contacts
#6
In a relay, what is the role of the coil?
To provide mechanical support
To generate magnetic field
To act as a switch
To control voltage
#7
What is the primary difference between a contactor and a relay?
Size
Current rating
Voltage rating
Functionality
#8
Which type of relay is commonly used in motor control circuits?
Thermal relay
Time delay relay
Overload relay
Latching relay
#9
What is a 'seal-in' circuit in the context of relays?
A circuit that prevents current leakage
A circuit that maintains relay operation after initial actuation
A circuit that prevents overvoltage
A circuit that controls the speed of a motor
#10
In a motor control circuit, what does the 'holding contact' of a contactor do?
Maintains the contactor coil energized after the start button is released
Provides power to the motor
Cuts off power to the motor in case of overload
Acts as an emergency stop
#11
What is a characteristic feature of a magnetic contactor?
It operates silently
It has no moving parts
It uses an electromagnet to control contacts
It can handle only DC current
#12
What is the function of a 'control relay' in an electrical system?
To regulate current flow
To provide emergency shutdown
To control the operation of other devices
To measure voltage
#13
What is a 'differential relay' commonly used for in electrical systems?
To detect overvoltage
To protect against short circuits
To measure current flow
To detect faults by comparing currents or voltages
#14
What is the typical application of a mercury-wetted relay?
In low-voltage circuits
In high-voltage circuits
In sensitive signal switching applications
In motor control circuits
#15
What is a 'time-delay relay' primarily used for?
To delay the start of a motor
To protect against short circuits
To regulate voltage
To measure current flow