CH 11 Test for 3 March Flashcards
The temperature in any structure, regardless of age, location, or design, can be maintained at comfortable levels with a _____
Thermostat
The _____ thermostat is used on control systems with a 24-volt supply.
Low-voltage thermostat
The _____ element of a thermostat is the part that moves when a change in temperature is detected.
Thermostat controlling
In a remote bulb thermostat, as the temperature of the _____ changes, as will the pressure exerted on the diaphragm.
Medium
In a remote bulb thermostat, the pressure exerted by the diaphragm on the mechanical linkage will open and close a set of _____
Contacts
The _____ thermostat is commonly used to control the temperature of any medium whether liquid or vapor, in many applications.
Remote Bulb
_____ are stationary inductive devices that transfer electric energy from one circuit to another by induction
Transformers
A heating thermostat closes on a(n) _____ in temperature
Drop
What is the difference between a step-down transformer and a step-up transformer?
Step-down: primary winding has more turns than secondary.
Step-up: secondary winding has more turns than primary.
What are the two windings associated with a transformer?
Primary and secondary
What are the two methods that enable thermostats to be snap-acting?
- Small magnet placed to close contacts firmly.
- Mercury in a bulb causing it to move to a position where the mercury makes good electrical connection between the electrodes in the bulb
What is the basic function of a thermostat?
Reacts to temperature by the opening or closing a switch.
Transformers are rated by their primary voltage, secondary voltage, and volt amperes VA. True or False.
True
Some commercial and industrial high-voltage equipment uses transformers that drop the line voltage to 240 or 120 volts. True or False.
True
Most residential and small commercial installations uses a 12-volt control system. True or False.
False
The transformer for a residential unit is used to convert line voltage to 24-volts. True or False.
True
Transformers are 100% efficient. True or False.
False
The bimetal thermostat derives its name from the fact that it uses three similar metals. True or False.
False
The transformer in a heating or cooling system provides the low-voltage power source for the control circuit. True or False.
True
The difference between a line voltage and a low-voltage thermostat is in the size of the bimetal element. True or False.
False
