D-1 Flashcards
(89 cards)
1
Q
Definition of Compound
A
Contains atoms of more than one type
2
Q
How many valence electrons would you find in
A) Conductor
B) Semi-conductor
C) Insulator
A
A) 1-3
B) 4
C) 5-8
3
Q
Definition of the Fundamental laws of charged bodies?
A
Like charges repel, unlike charges attract
4
Q
Two useful applications of electrostatic charge?
A
- Spray painting
2. Sandpaper manufacturing
5
Q
Two hazards of electrostatic charge?
A
- Lightening
2. Fuel handling
6
Q
6 methods that will create a difference of potential?
A
- Friction
- Chemical
- Pressure
- Heat
- Light
- Magnetism
7
Q
How many electrons are equal to one coulomb?
A
6.23*10^18
8
Q
Definition of voltage?
A
Potential difference
9
Q
Definition of resistance?
A
Opposition to electron flow, measured in ohms
10
Q
Define Ohms law?
A
The current flowing in an electric circuit that is directly proportional to the applied voltage and inversely proportional to the Resistance of the current
11
Q
Define Watts law?
A
The power in a circuit equals the product of the voltage and the current in the circuit
12
Q
Formulas for Ohms law?
A
- E=I*R
- I=E/R
- R=E/I
13
Q
Formulas for Watts law?
A
- P=I*E
- I=P/E
- E=P/I
14
Q
List the four main types of electrical drawings
A
- Pictorial
- Schematic
- Wiring
- Block/Line
15
Q
What is the difference between a block diagram and a line diagram?
A
Block - Uses blocks
Line - Uses symbols
16
Q
3 Characteristics of one-line diagrams
A
- Don’t show actual circuit position of components
- Labelled with name, type, catalog #
- No return path
17
Q
What does a wiring diagram show?
A
Actual accurate infromation
18
Q
On a wiring diagram when theirs a dot where two wires cross what does that mean?
A
That the wires are connected
19
Q
What does a schematic diagram show?
A
The electrical relationship
20
Q
Definition of circuit?
A
Circular journey or loop
21
Q
What 3 condition’s MUST exist for a complete circuit?
A
- Source
- Load
- Conductor
22
Q
Definition of short circuit
A
parallel path of low resistance
23
Q
Definition of open circuit
A
- Break in circuit
- No current flow
- Missing the source, load, or conductor
24
Q
What is provided by a switch in a circuit?
A
A way to open/close a circuit
25
Why are circuit breakers and fuses added to circuits?
To protect components from having too much current flow through
26
Which way does current flow from the source out through the load?
negative to positive
27
List three handling and storage precautions for electrical meters?
1. Shock and vibration
2. Tempature, humidity, and dust
3. Magnetic fields
28
What are the seven precautions you should consider when handling electrical measuring instruments?
1. Never use a resistant measuring device on a live circuit
2. Match meter to supply ex. DC-DC AC-AC
3. Always observe the meter polarity when connecting into the circuit
4. Check that the meter is orientated correctly to be read
5. Look directly )Straight on) at pointer
6. Select the range setting that gives the highest pointer deflection
7. Switch it off
29
How should a voltmeter be connected when taking measurements in a circuit?
In parralel
30
How should ammeters be connected into a circuit for taking measurements?
In series
31
List five items that should be observed when using an ohmmeter?
1. Never use on a live circuit
2. Disconnect one end of the device to be measured from the circuit
3. Everytime you change scales you must set it to zero again
4. Always turn it off when done
5. Do not touch both leads with your fingers
32
List the four things that should be observed when handling a wattmeter?
1. Connect the voltage coil in parallel with the load
2. Connect the current coil in series with the load
3. Do not exceed the power rating of the meter
4. You must observe the polarity of both coils
33
Definition of VOMS?
Volts, ohms, milliamps
34
What is a resistor?
Electrical component that introduces a specified amount of resistance into a circuit
35
How are resistors rated?
Ohms and watts
36
What are the three main classes of resistors?
1. Wire wound - Higher wattage
2. Film - Greater accuracy, lower wattage
3. Carbon composition - small, cheap, very low wattage
37
What is the main function of a switch?
Control the flow of current
38
What is the main function of fuses and circuit breakers?
Break circuit before damage is done
39
What should switches be marked with?
Rated voltage and current
40
List four different types of switches?
1. Dimmer switch
2. 3 way switch
3. 4 way switch
4. Single pole switch
41
List the three basic types of fuses?
1. Cartridge fuses
2. Plug fuses
3. Renewable link fuses
42
What is the most common type of circuit breaker?
Moulded case breaker
43
What is the function of a trip element in a circuit breaker?
Trigger the operating mechanisms in the event of a prolonged overload or excessive current magnitude and cause the circuit breaker to open
44
What are the two basic types of trip elements?
1. Thermal trip element
| 2. Magnetic trip element
45
Definition of oxidation?
Result of oxidizing or being oxidized
46
Definition of Ductility
Ability of a material to be drawn into a wire
47
Definition of malleability
Ability of a material to be rolled or hammered into thin sheets
48
Why s copper the most commonly used conductor?
- Easy to work wit
- Does not oxidize much
- Solders readily
49
What are three major problems of using aluminum as a conductor?
1. Oxidize forms easily
2. Aluminum reacts with some other metals
3. Cold flow
50
What are the three shapes a bus bar can come in?
1. Solid square
2. Solid rectangle
3. Hollow tube
51
What are the purposes of the conductor insulation?
To prevent unwanted flow of electrical current, such as ground faults, short circuits or electric shock.
52
List five types of insulating materials used for conductors?
1. Enamel
2. Varnished cambric
3. Rubber
4. Thermoplastic
5. Minerals
53
Definition of power circuit wiring?
means conductor and cable installation for the distribution of electrical energy within residential, commercial, and industrial buildings
54
What s the difference between the service equipment and the branch circuits?
Service equipment- Main power source for all other circuit wiring
branch circuits- Supply lightening, receptacle, heaters, dryers, motors
55
What does the code define as low voltage?
31v -750v
56
What does the code define as extra low voltage?
30v or less
57
List three ways in which a body may receive an electrostatic charge?
1. Friction
2. Conduction
3. Induction
58
Formula for line drop
E=i*r
59
Formula for line loss ?
P=i^2*r
60
Formula for voltage drop ?
Eload=esupply-edrop
61
Definition of matter ?
Anything that occupies space or has mass. It can exist in any of 3 states. Liquid, solid, gas
62
What is the difference between an atom and a molecule ?
1. A molecule can be an an independent unit of compound or an element, but an atom can only be the smallest unit of an element
2. A molecule must be independent but the atom does not have to be
63
List three ways in which a body may receive an electrostatic charge ?
1. Friction
2. Conduction
3. Induction
64
Definition of field force ?
A force that acts at a distance without physical contact
65
Definition of polarity ?
Refers to the charge at one point with respect to another
66
List 6 methods of producing energy ?
1. Friction - triboelrctic effect
2. Chemical - electrochemical effect
3. Pressure - piezoelectric effect
4. Heat - thermocouple
5. Light - photovoltaic cell
6. Magnetism - electromagnetic effect
67
State the law of conservation of energy ?
Energy can neither be created or destroyed
68
Formula for voltage ?
Joules/ coulomb
69
Formula for Amps
A=coulomb/second
70
Formula for efficiency ?
Efficiency= output watts/input * 100
71
Formula for horsepower ?
Hp=out/746
72
Definition of load ?
A device that changes electrical energy into other forms of energy
73
What will happen if you connect a DC meter to the wrong polarity ?
May be damaged as the pointer tries to deflect the wrong way
74
Definition of parallax Error?
The type of reading error that takes place when you do not look at the needle straight on
75
What are the three ratings you must be careful not to exceed when you are using a wattameter ?
1. Voltage coil
2. Current coil
3. Power
76
Voltmeters ?
Used to measure a difference of potential between two points
77
Ammeters ?
Designed with as low a resistance as possible so that they do not add unwanted resistance to the circuit
78
Wattmeter ?
Has four test leads. Two are for measuring current, and two for voltage
79
Ohmmeter?
Used to measure resistance
80
Colour code
```
Black -black
Boys - brown
Rape - red
Our - orange
Young - yellow
Girls - green
But - blue
Violet- violet
Goes- grey
Willings - white
Sometimes for gold
Sometimes for silver
Sometimes for nothing at all
```
81
What three purposes are resistors used ?
1. Limit current
2. Provide a change in voltage
3. Produce heat
82
In what unit is resistor rated ?
Ohms and watts
83
Identify 3 types of fixed resistors ?
1. Wire round resistor
2. Film resistor
3. Carbon- composition
84
Which resistor has the lowest watts rating ?
Carbon-composition resistors
85
What Ratings should switches have marked on them ?
Rated voltage and current
86
Snap switches ?
Used to control incandescent and fluorescent lamps
87
What shortcoming did the original Edison's fuse have ?
Could easily be replaced with one of higher amp rating
88
Definition of conductor ?
A material that allows electrical current to flor with relative ease
89
4 factors effecting resistance ?
1. Natural resistance
2. Length
3. Area
4. Temp
