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Instrumentation > Elect Theory N Safety > Flashcards

Elect Theory N Safety Flashcards

1
Q

2 main categories of resistors

A
  • fixed
  • variable
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2
Q

3 basic types of fixed resistors :

A
  • Composition resistors
  • film resistors
  • wire wound resistors
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3
Q

The most commonly used fixed resistor :

A

Composition

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4
Q

2 types of variable resistors

A
  • Rheostats
  • potentiometer
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5
Q

Basic difference between rheostat and potentiometer

A

Rheostat has 2 connection points
Potentiometer has 3

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6
Q

Res value
A) 2R2
B) 220k
C) 2M2

A

A) 2.2 ohm
B) 220 000 (×1000)
C) 2 200 000 (× million)

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7
Q

Resitor color code 1st color

A

1st digit

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8
Q

Resistor color code 2nd color

A

2nd digit

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9
Q

Redistor color code 3rd color

A

Multiplier

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10
Q

Resistor color gold
a) 4th position
B) 3rd position

A

A)+- 5%
B) .1

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11
Q

Resistor color code silver
A) 4th position
B) 3rd position

A

A)+- 10%
B) .01

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12
Q

Resistor color code no 4th band

A

+- 20%

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13
Q

Resistor color code black:
A) first color
B) second color

A

Both are 0

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14
Q

If there are more than 4 color bands:

A

1 to 3) #s
4) multiplier
5) tolerance
6) temp coefficient

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15
Q

Resistor color code yellow,violet, red, silver rating

A

4700 +- 10% (4.7 k ohm)

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16
Q

Res colors green,black,brown rating

A

500 ohms +- 20%

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17
Q

3 distinct ratings of resistors

A

A) resistance (ohms)
B) power (watts)
C) tolerance

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18
Q

Resistor color code

A

Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Grey
White
Gold

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19
Q

A material with easily freed electrons is called

A

A conductor

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20
Q

Def: static electricity

A

Build up of charge in an insulated object

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21
Q

Static electricity:

A

Build-up of charge in an insulated object

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22
Q

A ______ represents the quantity of charge of a huge # of electrons

A

Culomb

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23
Q

Def amp ,:

Current formula

A

Rate of movement of charges past a point

Current = quantity of charge/ time

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24
Q

Conventional current flows from ____ to _____

A

Positive to negative

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25
Q

If current flows from - to + it is _____ flow

A

Electron

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26
Q

Why dont you connect an ammeter in parallel:

A

The low resistance of the ammeter will cause a large current flow and blow the fuse

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27
Q

Voltage is derived :

A

From the measurement of difference in charge

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28
Q

6 sources of emf

A

1) magnetic
2) chemical
3) friction
4) heat
5) pressure
6)light

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29
Q

Formula for conductance

A

G = 1/R

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30
Q

Ohms law

A

V / I ×r

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31
Q

What force maintains a difference in charge?
Its abbreviation?

A

Electromotive force
Emf

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32
Q

4 factors affecting conductor resistance

A

1) cross sectional area
2) length
3) type of material
4))temp of material

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33
Q

Resistance is directly _____ to conductor length

A

Proportional

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34
Q

Resistance is ______ to conductor cross sectional area

A

Inversely proportional

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35
Q

For most materials increase temp causes:

A

Increased resistance

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36
Q

At 20 degrees what is the resistivity of copper

A

1.72 × 10 ^-8

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37
Q

At 20 degrees what is the resistivity of aluminum

A

2.83 ×10^-8 ohms

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38
Q

Copper ohms per 1000m, how does it increase,?

A

3.27
Doubles every 3 gages ie:away 13 is 6.54, 16 is 13.08
Or goes up × 1.26 each gage

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39
Q

Base unit for temp

A

Kelvin

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40
Q

Base unit for amount of substance

A

A mol

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41
Q

Conductor resistance formula:

A

Ohms = resistivity × length / area
Resistivity is in ohm- meters

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42
Q

Temp resistance formula

A

R2 =R1(1+a(t2 -t1))
R1 initial temp res
a temp coefficient
T2 new temp
T1 initial temp

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43
Q

Dielectric strength def,:

A

Voltage required to cause a breakdown in insulation

44
Q

Unit for dialectic stength

A

Volts per millimeter

45
Q

Mili def

A

10 ^-3

46
Q

Micro def

A

10 ^ -6

47
Q

Nano def :

A

10 ^-9

48
Q

Pico def

A

10 ^-12

49
Q

A copper conductor is 150m long and has a resistance of .76. Whats the cross sectional area?

A

1.72 ×10^-8 ×150m /.76
= 3.4× 10^-6 m^2
Or 3.4 mm^2

50
Q

To measure the ohms for volt drop

A

De energized check across the load

51
Q

Valence electrons for
- conductors
- insulators
- semi

A
  • 1 to 3 cond
  • 4 semi
  • 5 to 8 insul
52
Q

Every 3 db _____ the strength of the noise

A

Doubes

53
Q

3 power calcs

A

P = VI
P =( V ^2)/ R
P = I^2 R

54
Q

Min battery voltage after supplying amp hour rating?

A

91% of Max

55
Q

Voltage leads current in an _____ circuit

A

Inductive

56
Q

Current leads voltage in a _____ cct

A

Capacitive

57
Q

Series cct :
Res
Volt
Amps

A

Add ohms
I is same
V different

58
Q

Parallel cct
Res
Volt
Amps

A

1 over ( 1 / res 1) (1 / res 2)
Volts same
Current varies

59
Q

In a series cct if R1 ohms are 3x larger than R2 then R1 voltage is ______ than R2

A

3x larger

60
Q

Series cct voltage across closed switch

A

0v

61
Q

Series cct voltage across open switch

A

Applied voltage

62
Q

Kirchoffs voltage law states:

A

The algebraic sum of all voltages in a closed cct = 0

63
Q

Parallel cct:
RT = 15.
R1 = 30
R2 = 120
R3 = x

A

X = 40

64
Q

Parallel cct
E =12 v
R1 = 24
R2 = 24
R3 = 12
Rt =? It =? R1 I?

A

Rt = 6 ohms
It = 2a
R1 i = .5a

65
Q

Kirchoffs current law:

A

All the current values entering a junction must equal the current values leaving a junction

66
Q

Def : inductance

A

Property of a cct that opposes change in current

67
Q

Def induction

A

Process by which h a voltage is produced by the interaction of a conductor and a magnetic feild

68
Q

Amount of emf is directly proportional to change of flux is whos law

A

Faradays

69
Q

Current from an induced voltage develops a flux that opposes a change in the original flux is whos law

A

Lenz’s law

70
Q

With a coil what 4 factors up inductance

A

1) more turns
2) higher permeability
3) bigger core area
4) shorter path

71
Q

Class 1 area def:

A

Flammable gasses n vapours

72
Q

Class 2 area def:

A

Dust

73
Q

Class 3 area def:

A

Igniteable fibers/ flying

74
Q

Zone 0 def

A

Hazard present most of the time under normal conditions

75
Q

Zone 1 def:

A

Next to zone 0 , flammable gasses vapors likely more than 10 but less than 1000 hrs/yr

76
Q

Zone 2 def

A

Next to zone 1. Explosive conditions don’t normally exist . Less than 10 hrs/yr

77
Q

When generating voltage what 3 factors determine the amount

A
  • density of flux
  • length of conductor in mag feild
  • rate at which it cuts lines of force
78
Q

Def : 1 alternation
# of degrees

A

When a conductor passes 1 pole
180

79
Q

Def : 1 cycle

A

2 alternations

80
Q

Difference between generator and alternator

A

Generator: rotating conductor, stationary feild
Alternator: opposite

81
Q

If Vpk is 10v and sine @ 20 degrees:
Voltage is:

A

Vpk × sin20
10 × .342
3.42 v

82
Q

120v 60 hz supply. In series:
-20 ohm resistor
- 20 Xl / 5 ohm coil
- 12 Xc capacitor
Zt? It?

A

Xt 20 - 12 =8 vars
Rt 6 +5 ohm = 11 ohm
Pythagoras = 13.6 Ohm Zt
120/ 13.6 = 8.82 It

83
Q

of time constants to reach steady state

A

5

84
Q

% increase per time constant

A

63.2%

85
Q

Frequency calc formula: on a generator

A

F =( # of poles × rpm) / 120

86
Q

Max volts of 120 v cct
Min

A

120 / .707(sin 45) = 169.7
120 × .707 = 84.84

87
Q

Def power
Unit

A

Rate of doing work
Watt

88
Q

Power formula ( watts)

A

Energy/time ( j/s)

89
Q

A primary cell is

A

Non rechargeable

90
Q

Battery: secondary cell

A

Rechargeable

91
Q

Retentivity

A

Ability of a material to retain residual magnatism

92
Q

Silicone steel reduces

A

Hysteris losses

93
Q

Laminations reduce

A

Eddy current losses

94
Q

60/40 solder is made of

A

60 % tin
40 % lead

95
Q

Can you use crimps on solid wire?

A

No

96
Q

Wattage of a soldering gun

A

Usually about 40

97
Q

Electronics: what is EPA

A

Electrically protected area

98
Q

Electronics what is ESD

A

Electro static discharge

99
Q

Temp coefficient of aluminum/ copper

A

. 0039

100
Q

Efficiency of a 1.5 hp motor that draws 10 A from a 120 V supply

A

((746 × 1.5) / 10 A × 120 V ) × 100%
93.25 %

101
Q

A 90 amp hour 12v battery can deliver ___ amps for 30hrs and not drop below _____ volts

A

1) 90/30 = 3a
2) 12 × .91 = 10.92

102
Q

Normally what direction does magnetic flux travel, which pole to pole

A

North to South

103
Q

Right hand rule :
1) thumb
2) 1st finger
3) 2nd finger

A

1) direction of current
2) direction of flux
3) direction of force

104
Q

Ac positive alternation is
Negative

A

0 - 180
180 - 360

105
Q

Dc time constant
Cct is 12vdc has an inductor with 3 ohms n .2 henries. How long to reach steady state?

A

Current: 12 / 3 =4
T = L/R : .2/3 = .67
5 time const so .67 x5 = .33 sec

Instrumentation (6 decks)

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