final

Question 1

Electrons that are no longer bound to their atoms

Answer 1

what are free electrons

Question 2

electric current that regularly reverses direction is called

Answer 2

alternating current

Question 3

electric current is measured in

Answer 3

amps

Question 4

electrical potential is

Answer 4

the ability to make current flow

Question 5

In a basic electric circuit with a steady potential, when resistance increases

Answer 5

current decreases

Question 6

In a series circuit, total resistance is determined by

Answer 6

adding the sum of all individual resistances

Question 7

in a parallel circuit

Answer 7

the voltage stays the same throughout the circuit

Question 8

What is the current draw of a 1,200 w operating on a 120 v AC power supply

Answer 8

1,200 w/ 120 v = 10 a

Question 9

AC power can be converted to DC power through use of component called

Answer 9

rectifiers

Question 10

most hvac systems operates on

Answer 10

alternating current

Question 11

if a conductor is coiled as in a relay coil, then passing current through it will the magnetic field

Answer 11

intensify

Question 12

what does a transformer do

Answer 12

increases or decreases incoming voltage

Question 13

impendance is the combined effect of

Answer 13

resistance, inductive reactance, and capacitive reactance

Question 14

a delta three phase power supply provides

Answer 14

240 v between the legs

Question 15

what unit specification should be used to size the overcurrent protection

Answer 15

the maximum overcurrent protection (mocp)

Question 16

what specification on the unit data plate should be used to size the power wire

Answer 16

the minimum circuit ampacity (mca)

Question 17

the voltage between any let of a 480 v WYE transformer and ground is

Answer 17

277 v

Question 18

the different color used for the color bands on resistors represent

Answer 18

numbers

Question 19

when the 3rd color band is silver, it represents

Answer 19

the multiplier for the resistor

Question 20

This component uses the properties of AC induction to step up of step down voltage for particular hvac applications

Answer 20

transformer

Question 21

the primary winding of a 120 v transformer has 200 turns. the secondary winding has 20 turns. what is the secondary winding voltage

Answer 21

12 v

Question 22

an electrical component that stores energy when an electric charge is forced onto its plates is called a

Answer 22

capacitor

Question 23

compared to motor capcacitors, paper and film capacitors are

Answer 23

smaller in rating and physical size

Question 24

what is the common sensing element used in as electronic thermostat

Answer 24

a thermistor

Question 25

controls that use human hair for sensing are

Answer 25

humidistats

Question 26

which type of thermostats provide the closest temperature control

Answer 26

electronic low voltage thermostats

Question 27

what is used as the sensing element in a mechanical humidistat

Answer 27

a nylon ribbon or hair

Question 28

the electric switching in an electronic thermostat is often done by

Answer 28

small relays

Question 29

the thermostats on most residential AC sytems are

Answer 29

low - voltage thermostats

Question 30

line voltage thermostats normally operate on `

Answer 30

120 v

Question 31

What is the purpose of staging thermostats

Answer 31

to allow systems to operate at reduced capacity

Question 32

a control that respond to changes in pressure is called a

Answer 32

pressure switch

Question 33

when do normally open relay contacts close

Answer 33

when the relay coil is energized

Question 34

what device can best be described as an electrically operated switch

Answer 34

a relay

Question 35

a fuse protects an electrical circuit by

Answer 35

melting when excessive current flows throuygh it, opening the circuit

Question 36

when replacing a fuse youu must match the

Answer 36

volt, amp, instantaneous current, and physical size

Question 37

Why are manufacturers replacing relay logic systems

Answer 37

solid state logic systems operated faster use less power and can control more functions

Question 38

this electrical component allows current to flow in only one direction and operates similar to a check valve

Answer 38

diode

Question 39

a triac can be described as

Answer 39

2 silicon controlled rectifiers (scr) in parallel

Question 40

examples of load devices include

Answer 40

motors, resistance heaters, and solenoid valves

Question 41

examples of control devices iniclude

Answer 41

thermostats, pressure switches, and humidistats