WorksheetsNCCER Electrical 2 Module 11
Total questions: 32
Worksheet time: 16mins
The function of a shading coil in a contactor is to
De-energize the primary coil
Unlatch the relay
Interrupt an electrical circuit
Prevent contact chatter
What is the major difference between a contactor and a motor starter
Normally closed
Normally open
Electromagnetic
Controllers
A motor is connected L1 to T1, L2 to T2, and L3 to T3. To reverse the motor, the leads need to be connected _____.
L1 to T3, L2 to T1, and L3 to T2
L1 to T2, L2 to T3, and L3 to T1
L1 to T3, L2 to T2, and L3 to T1
L1 to T1, L2 to T2, and L3 to T3
If contactor action is dependent on current flow, the contactor is described as _____.
Electrically held
Mechanically held
Reversing
Solid state
Which of the following is TRUE regarding lighting contactors?
Lighting contactors are frequently controlled by a two-wire pilot device
Lighting contactors can be used on motor circuits.
Lighting contactors can be used on motor circuits.
The contacts in lighting contactors are rated for low inrush currents
Mechanically held relays and contactors are often used in auditoriums because _____.
They have fewer coils than electrically held devices
They are quieter than electrically held devices
They are less expensive than electrically held devices
They are more reliable than electrically held devices
The lubrication of a large industrial motor at prescribed intervals can be accomplished using a _____.
Control relay
Timing relay
Oil-sensing relay
Mechanical interlock
A single-pushbutton contact can be used to control the sequence of operation of several loads by using a _____.
Switch
Multi-pole relay
Solenoid
Multi-coil relay
A motor overload relay consists of a current-sensing unit and a mechanism activated by the sensing unit that _____.
Dissipates excess current
Decreases motor speed
Trips an alarm
Opens the motor circuit
An opto-isolated solid state relay is activated by _____.
Heat transfer
Magnetism
Current
Light
The two classifications of overload relays are thermal and _____.
Eutectic
Shading
Magnetic
Bimetallic
Which of the following is a nonrenewable device?
Solenoid
Melting alloy overload relay
Time-delay fuse
Bimetallic overload relay
Increasing the armature spring force in a relay will result in _____.
Lower pull-in voltage
Lower current values
Lower drop-out values
Higher drop-out values
The overload relays in machines associated with continuous processing typically activate a(n) _____.
Alarm circuit
Transformer
Motor circuit
Shut-off circuit
Power to operate low-voltage switching systems is supplied by _____.
The line supplying the load
The switch leg
The relay
A transformer
Which of the following is a probable cause of relay-controlled equipment failing to start when the contactor is closed?
One contact not closing
Excessive residual magnetism
A grounded coil
Gummy deposits
The symbol shown in the figure provided is used to denote a low-voltage _____.
( symbol shown is a capital "T" in a diamond)
Transformer
Thermistor
Triac
Timer
Low-voltage remote control switching relays _____.
Do not use coils
Use a split low-voltage coil
Use a split high-voltage coil
Use three low-voltage coil
The panel for a low-voltage lighting control system enclosure should be mounted _____.
in an inaccessible location to avoid tampering
at least 6' away from the main panel
after all relays have been tested
at eye level between two studs
Which of the symbols shown in the figure provided is normally used to indicate a low-voltage switch with a separate pilot light?
A. (Rp)
B (Pl)
C (Sp)
D (R)
What term is used to describe the conversion of
electrical energy into linear motion in a relay?
The solenoid principle
The voltage principle
The current principle
Three-point Test
When a contactor circuit is energized, a _____
contact closes and a _____ contact opens.
normally open; normally closed
normally closed; normally closed
normally open; normally open
normally closed; normally open
The maximum tungsten/infrared load amperage for
a NEMA Size 0 magnetic contactor is _____.
5A
10A
18A
21A
A manual reversing starter uses _____.
a mechanical interlock
an electrical interlock
two separate coils
a single coil
Mechanically held relays would most likely be used
in a _____.
grocery store
cafeteria
sports arena
hospital
A single-contact device can be used to control
multiple loads using a _____.
single-pole relay
current amplifier relay
voltage amplifier relay
multiple-pole relay
A furnace might use an on delay to _____.
save energy during periods when the space is
unoccupied
avoid blowing cold air into the space when the
system starts up
prevent the system from cycling between
heating and cooling
prevent thermostat tampering
A type of relay controlled by a magnetic field is a(n)
_____.
opto-isolated relay
power transistor
triac
reed relay
A type of renewable overload device is a _____.
time-delay fuse
dual-element fuse
melting alloy relay
fusible link
The operating coil of a relay is designed to work
properly at _____.
80% to 110% of the rated voltage
90% to 100% of the rated voltage
95% to 105% of the rated voltage
100% of the rated voltage only
A device that allows relay to be controlled as a
group while still allowing individual switch control is
a _____.
pilot switch
master sequencer
three-way switch
rectifier
Where low-voltage cable must be run parallel with
high-voltage cable, it should be separated by a
minimum of _____.
4" (100 mm)
6" (150 mm)
8" (200 mm)
12" (300 mm)