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Year 1 Electrical BC > D6 > Flashcards

D6 Flashcards

1
Q

How many valence electrons do insulators have?

A

five or more

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2
Q

How many valence electrons do conductors have?

A

3 or less

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3
Q

How many valence electrons do semi conductors have?

A

exactly 4

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4
Q

What are the two most commonly used semiconductor elements?

A

silicon and germanium

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5
Q

Silicon is the most common semiconductor element because?

A

it can with stand higher temperatures

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6
Q

Purified semiconductor materials arrange themselves into a

A

crystal-lattice structure

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7
Q

Semi-conductor atoms tend to share their valence electrons in an

A

covalent bond

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8
Q

To make a semiconductor a better conductor, a small amount of impurity is introduced this is called

A

doping.

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9
Q

Creating a N-type semiconductor a ________ atom is used

A

pentavalent

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10
Q

A N-type semiconductor has an excess of

A

electrons and is negatively charged

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11
Q

To create a P-type semiconductor a ___________ element is used.

A

trivalent

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12
Q

List three trivalent atoms

A

aluminum
boron
gallium

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13
Q

List three pentavalent atoms

A

arsenic
antimony
phosphorous

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14
Q

A P-type semiconductor has an unfilled

A

hole and is considered positively charged or less negative

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15
Q

Semiconductors have a negative temperature coefficient of resistance. explain

A

this means that as the temperature increases the resistance decreases.

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16
Q

When a joining a P-type material to a N-type material it creates a ____________ potential

A

barrier

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17
Q

The barrier potential for silicon diodes is

A

.7 Volts

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18
Q

The barrier potential for germanium diodes is

A

.3 Volts

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19
Q

When the cathode is more positive than the anode (reverse bias) how is the barrier potential at the PN junction is strengthened.

A

free electrons in the N-type material attracted to the positive side
the holes in the P-type material are attracted toward the negative
depletes the junction region of any available charge carriers thus blocking current flow.

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20
Q

When an external voltage is applied that makes the cathode more negative than the anode the barrier junction will weaken and

A

current will flow this is called forward bias

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21
Q

As the current in a diode increases the resistance tends to decrease due to the negative temperature coefficient of semiconductors this

A

decrease in forward resistance combines with the increase in current so that the small voltage drop remains the same.

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22
Q

What is PIV

A

Peak inverse voltage is the point at which a diode can no longer block current flow. Beyond this point the diode breaks down and current avalanches

23
Q

For a diode to conduct it must be

A

forward-biased

24
Q

To remember anode and cathode (only for conventional current flow

A

Current flows alphabetically, anode to cathode

25
Q

When a diode is connected across an inductive DC load so as to prevent arcing during switching operations, it is called

A

freewheeling diode

26
Q

Describe a Zener diode

A

designed to operate beyond its breakdown voltage rating in the reverse direction (reverse bias)

27
Q

If a silicon Zener diode is dropping .7 volts across it what is wrong?

A

It is hooked up back to front.

28
Q

Define Zener voltage

A

is the regulated voltage that is maintained across the Zener diode when it operates with reverse bias.

29
Q

What are Zener diodes good for?

A

voltage regulator

30
Q

How does a Zener diode regulate voltage?

A

When the breakdown voltage is reached the drop-off is sharp keeping the voltage constant.

31
Q

What must we do when installing a Zener diode as a voltage regulator?

A

DC input voltage must exceed the Zener voltage
Hook Zener diode in reverse-bias
instal series current-limiting resistor
Connect load in parallel with Zener diode

32
Q

Photodiode is a special PN junction diode in which

A

light striking the junction increases the conductivity of the diode

33
Q

If two blocks of N-type semiconductor material are separated with a very thin layer of P-type semiconductor material then

A

a NPN transistor is created

34
Q

If the two outer blocks are made of P-type semiconductor, and if the separating layer is N-type semiconductor then

A

a PNP transistor is formed

35
Q

Signal transistors

A

are used in the milliwatt range

36
Q

Power transistors

A

are used in the watt range

37
Q

What does BJT stand for?

A

bipolar-junction transistor

38
Q

Transistor terms: Q

A

transistor

39
Q

Transistor terms:Ib

A

Base current

40
Q

Transistor terms:Ic

A

Collector current

41
Q

Transistor terms:Ie

A

Emitter current

42
Q

Transistor terms:Rb

A

Base circuit resistance (control)

43
Q

Transistor terms:Rc

A

Collector circuit resistance (load)

44
Q

Transistor terms:V Rb

A

Voltage drop across base circuit resistance

45
Q

Transistor terms: V Rc

A

Voltage drop across collector circuit resistance

46
Q

What is the advantages of using a transistor as a relay instead of a coil/contact relay?

A 
the transistor has no
contacts to pit
no coil to burn out
no moving parts to wear out
it is completely solid-state
47
Q

the magnitude of the base current actually controls

A

the amount of collector current that can flow

usually by the beta factor or the transistor

48
Q

Transistor terms: Beta

A

expresses the magnitude of collector current controlled by a specific value of base current

49
Q

Transistor terms: Alpha = Ic/Ie

A

since the emitter current is always greater than the collector current alpha is always less then 1

50
Q

Transistor terms: Cut off

A

if the base current is reduced to a value close to zero then no collector current is allowed to flow.

51
Q

Transistor terms:Saturation

A

If increasing the base current any further cannot allow any more collector current to flow the transistor is said to be saturated.

52
Q

Which way does the arrow on a transistor diagram point?

A

from P to N

53
Q

Transistor terms: biasing

A

setting the value of Vce for a transistor

Year 1 Electrical BC (14 decks)

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