8-11 123
__________________ magnetism is created when a piece of iron is placed in a magnetic field.
Induced
____________ poles of magnets repel each other.
Like
__________ has established standard motor dimensions.
NEMA
____________ motors are used when very small starting and running torques are required.
Shaded pole
_______________________ is the strength that a motor produces by turning, either while starting or running.
Torque
A contactor is used to control an electrical load in a control system.
True
A cooling thermostat closes on a rise in temperature.
True
A load that is purely resistive in nature with no coil to cause induction is called a resistive or non-inductive load.
True
Contactors are rated by the amperage they can carry.
True
Contactors are used on larger loads than relays are because their contacts are larger.
True
Contactors are used to make and break a set of contacts that control the voltage to loads in heating and air conditioning systems.
True
Contacts are made of silver or cadmium which will resist sticking
True
Fuses are primarily used to protect non-inductive loads that do not draw LRA on start up.
True
If the VA rating of a transformer is 75 VA and the output voltage is 24 volts, the maximum amperage the secondary can handle without overheating is 3.1 amps.
True
If the contactor contacts become burned and pitted it is possible that they could develop resistance and cause a voltage drop.
True
If you check a single phase compressor motor and it is experiencing difficulty starting up, you can add a correctly sized start capacitor and potential relay to the electrical circuit and increase starting torque and possibly repair the compressor.
True
Overloads can be divided into two basic groups, thermal and magnetic.
True
The VA rating of a transformer divided by the low voltage output determines the maximum amps the secondary output can support without overheating.
True
The back electromotive force is the amount of voltage that is produced by the start winding of a motor while it is operating.
True
The back electromotive force is the controlling factor that causes a potential relay to drop the start winding out of the circuit once a single phase motor is up and running 75% full speed.
True
The chemical composition of contacts is such that they operate at cool temperatures of up to 125% of their current-carrying capacity.
True
The contacts in a remote bulb thermostat open and close contacts when the pressure in the bulb raises and lowers due to temperature changes.
True
The controlling element of a thermostat is the part that moves when a change in temperature is sensed.
True
The current relay, also known as the magnetic relay, is built like a solenoid, with a copper wire wrapped around a hollow steel core holding a steel plunger.
True
The difference between line voltage and low voltage thermostats is the amount of current they can carry.
True
The function of a thermostat is to make and break power to loads based on the temperature in a structure.
True
The pilot duty overload directly breaks the line voltage to a motor or load.
True
The potential realy is easy to check because there are only 2 components that need to be checked on it.
True
The simplest form of overload protection is a fuse.
True
The transformer for a residential air conditioning system is used to convert line voltage to 24 volts.
True
Transformers are rated by their primary voltage, secondary voltage, and voltamperes (VA).
True
Transformers are stationary devices that transfer electrical energy from one circuit to another by induction.
True
With the advancement of solid state starting relays, there is a start relay available now that has no moving parts called a PTC device.
True
The _____________________ consists of two aluminum plates with an insulator between them.
capacitor
The _____ motor produces a high starting torque, which is needed for many applications in the industry.
capacitor-start
The _____________ is a magnet produced through electricity.
electromagnet
The magnetic lines of force of a magnet that flow between the two poles are called _______________.
flux
The rotation of a shaded-pole motor is determined by _____.
location of shaded pole
The area that the magnetic force operates in is called a/an ________________.
magnetic field
_________________________ is the physical phenomenon that includes the attraction of an object for iron.
magnetism
A _______________ is the unit of measurement for the strength of a capacitor.
microfared
When going on a service call, the technician's appearance is _____________.
of utmost importance
To make an electric motor move continuously, there must be a ______________ magnetic field.
rotating
The ______ is the part of a motor that spins.
rotor
The ___________ capacitor is designed to stay in the motor circuit for the entire cycle of operation.
run
The capacitor- _____________ motor produces a high starting torque.
start
The_______________ is the stationary part of a motor.
stator
One of the most important aspects of the technician's job is _____.
the treatment of the customer
A heating thermostat closes on a rise in temperature.
False
A very common overload used in the industry is the bi-metal overload that uses three different metals to make a temperature sensitive device that moves contacts by expanding and contracting with temperature changes.
False
Coil characteristics depend on the type of wire but not the manner in which it is wound.
False
In an open type split phase, single phase motor, the start winding must be dropped out of the circuit once the motor is up and running at 35% full speed.
False
Inductive loads do not draw higher amperage at start up than they do once they are running full speed.
False
Most residential and small commercial HVAC systems use a 12 volt control system.
False
On all single phase motors, the starting amperage is less than the running amperage because the motor only stays in start mode for a second or so.
False
Relays are designed to carry more current so they are used on larger loads than contactors.
False
Relays can not be used to control loads in an HVAC system.
False
Split phase motors have a start and run winding that both stay energized the entire time the motor is operating.
False
The 3 primary parts that make up contactors and relays are the contacts, coil, and electrical connection points
False
The bi-metal thermostat gets it's name from the fact that it uses three similar metals.
False
The exact temperature in a structure can be maintained by a transformer.
False
The low voltage thermostat can carry more current than the line voltage thermostat.
False
The pilot duty overload directly breaks the line voltage power to motors and loads.
False
The primary winding in a thermostat induces a output voltage in the secondary.
False
The primary winding of a transformer is the output side of a transformer.
False
The running load amperage, RLA, is sometimes stated as the LRA on a motor nameplate.
False
The secondary winding of a transformer is the input side of a transformer.
False
The thermostat in a heating and air system provides the low voltage power for the control circuit.
False
Thermal overloads will trip and stop the load from operating when the magnetic field created in the circuit increases above the design trip point.
False
Transformers are 100% efficient
False
