ELEC UNIT 12

Question 1

(12.1) What old technology do transistors replace?

Answer 1

vacuum tubes

Question 2

(12.1) How are the terms “solid state” and “semi-conductor” different?

Answer 2

solid state refers to physical description of component, semiconductor refers to the electrical conductivity of component.

Question 3

(12.1) define semi-conductor

Answer 3

a conductor who’s conductivity is between that of an insulator and a highly conductive metal.

Question 4

(12.1) What 2 components make up a transistor?

Answer 4

the thermistor and the varistor

Question 5

(12.1) What is a thermistor

Answer 5

a semi-conductor with a positive or negative temperature/resistance coefficient.

Question 6

(12.1) What does a thermistor do?

Answer 6

a semi-conductor that’s resistance decreases as the applied voltage increases.

Question 7

(12.1) what materials are most common in semi-conductors?

Answer 7

germanium and silicon (silicon is most common)

Question 8

(12.1) What is an N-type material in a semi-conductor?

Answer 8

a semi-conductor paired with a material with free electrons (negatively charged material)

Question 9

(12.1) What is a P-type material in a semi-conductor?

Answer 9

a semi-conductor paired with a material with holes (a lack of electrons, making it positively charged).

Question 10

(12.1) what is the difference between diodes and rectifiers?

Answer 10

diodes are rated at less than 1 A, and rectifiers are rated at more than 1 A.

Question 11

(12.1) What do diodes and rectifiers do?

Answer 11

they allow current flow in one direction, which makes them useful in rectifying AC into DC.

Question 12

(12.1) What is the symbol for a diode or a rectifier on a schematic diagram?

Answer 12

Question 13

(12.1) What are the 2 types of transistors?

Answer 13

NPN and PNP.

Question 14

(12.1) What are transistors used for?

Answer 14

they are used as a switch or to amplify a signal (like radio, but for closing another switch or driving a small motor).

Question 15

(12.1) What do the 3 parts of a transistor do?

Answer 15

base - activates transistor
collector - positive end
emitter - negative end

Question 16

(12.1) what are triacs?

Answer 16

transistors but with two diodes. They are used as switches and relays in AC circuits.

Question 17

(12.1) what is the symbol for triacs in a schematic diagram?

Answer 17

Question 18

(12.1) What is the symbol for LEDs in a schematic diagram?

Answer 18

Question 19

(12.4) What does a one-function electronic control do?

Answer 19

solid-state devices that control one thing, like start assist a motor, prevent short cycling, etc.

Question 20

(12.5) What do anti-short-cycling-timers so?

Answer 20

they prevent electrical loads from starting and stopping in rapid secession (from 30 sec to 5 min). as the device heats, its resistance decreases, allowing current to pass through.

Question 21

(12.8) What controls the entire operation of a heat pump?

Answer 21

the heat pump electronic module

Question 22

(12.9) What are the electronic control boards on gas furnaces usually called?

Answer 22

the ignition module

Question 23

(12.9) What is pilot safety mode on the ignition module?

Answer 23

supervises the operation of the ignition of the fuel.

Question 24

(12.9) When does lockout happen on a gas furnace?

Answer 24

when the fuel fails to ignite.