Electrical Systems, Mod 1-4 Flashcards
MEMORIZE THIS!!!!!
what is the area in mm^2 and the Ohms per 1000m Copper at 20°C, for SIZE 10 AWG WIRE?
AWG No. 10
5.26 mm^2
3.270 ohms per 1000m
What is the size difference between each wire? Percent.
26% or 1.26
What is the formula for calculating the area of a circular conductor? METERS AND MILLIMETERS ONLY!!
A=πr^2
A=π • r^2
What is the formula for calculating the radius/ cross sectional area?
r=d/2
Radius= diameter ÷ 2
The area of a conductor in cmils is represented by what formula? Formula if given inches?
Area= d^2 (cmil)
d= ____inches • 1000 (to get mil from inches)
Formula for calculating resistance and length?
R= (length/ 1000m)• resistance per 1000m
Ohms Law formula.
I= E/R
E= I•R
R= E/I
Fuses connections give off a __________ reaction
Exothermic
Fusing can be used to join copper and ______ or copper and _______.
Copper
Aluminum
Mechanical Connections are non reusable. True or false.
False.
Compression connections are reusable, true or false?
False
What are the four common classes of terminations/ connections?
Soldered
Fused
Mechanical
Compression
When tinning something, what are you covering the conductor in?
Solder
What must you do before soldering wire?
Electrically and mechanically secure
Wire strippers can be used for No.10 AWG and larger for stripping, true or false?
False. It’s No. 10 and Smaller.
What is pencilling?
The progression of angles cuts along a wire at 30°.
Why must you never ring a wire at 90°?
Causes scoring of the conductor and can break if you try to shape it or subject to vibration.
What properties must be considered for reinsulation?
Environmental conditions
Conductor Material and Sizes
Maximum temperatures
Voltage rating
Reinsulating materials include:
Electrical tape
Splicing compound
Heat shrink tubing caps
Preformed insulating covers/ boots
What is a tap?
A joint in a conductor where one wire is smaller than the other
What is a termination?
The “destination” of a control device.
Do mechanical terminations use a screw and lug?
Yes
For solid conductor terminations under a screw, what is the maximum wire size?
No. 10 AWG
True or False:
When making a hook with a wire to go under a screw, it’s best to put it in a clockwise direction
True
Twist on connectors are approved for use with any conductor size? True or false.
False.
Each twist on connector corolates to a specific conductor size.
When using larger conductors like split bolts and cable clamps, what is the most important step?
Filing down sharp edges.
What are 4 problems, Aluminum conductors present when making terminations?
Oxidation
Cold flow
Thermal Expansion
Galvanic Corrosion
What is a deterrent for oxidation?
Antioxidant compound immediately applied after cleaning.
What is Cold Flow?
The gradual flow of material away from a high pressure area
What is thermal expansion?
Aluminium conductors expand 38% more than copper in various temperature environments. Which can lead to loose connectors.
What is galvanic Corrosion?
When 2 dissimilar metals are together in the presence of moisture.
What is the correct orientation of copper and aluminium wires in a connector?
Aluminium on top and copper on the bottom.
What are the 2 symbols to indicate a connector is approved for aluminum?
CO/ALR
CU/AL
What are the 2 types of resistors?
Fixed and Variable
What are the three types of fixed resistors?
Composition
Film
Wire-wound
Composition resistors are a carbon based alloy with a ______.
Binder
What is the core of a resistor made of?
Ceramic or Glass
Can a variable resistor have its value changed?
Yes
What is a Rheostat?
A variable resistor that has 2 connection points.
What is a potentiometer?
A variable resistor that has three connection points.
When resistors use the letter ‘R’, what are the three ways the resistance value can be calculated with these variables:
R22
2R2
22R
The R is meant to show a decimal place
0.22
2.2
22
The R variable is only for resistors with more or less than 1000 ohms?
Less
The letter ‘K’ on resistors is used for values between ______ and ______.
1,000 and 1,000,000
What are three ways the resistance is measured based on the label?
2K2
22K
220K
2200
22000
220000
The letter ‘M’ on resistors is only used if the value is ________ or more.
One million
What is the resistance value of the label reads:
2M2
22M
2,200,000
22,000,000
True or false:
A resistor can not burn your skin
False
How is power rating measured?
Watts
Does a resistor convert electrical to heat or heat to electrical?
Electrical to heat
What is a tolerance rating?
Degree of accuracy. Measures in percent.
Using the resistance colour code table, what would the resistance rating be if the colours were:
First band- green
Second band- blue
Third band- black
Fourth band- silver
5
6
1
+- 10%
56•1= 56
56 ohms +-10%
Determine the resistance with the following digits:
2
7
1
27 • 10^1= 270
Determine the resistance with the following digits:
5
R
9
2
5.92 ohms.
What are voltmeters used to measure?
Volts
What are Ammeters used to measure?
Amps / electrical current
What is an Ohmmeter used to measure?
Ohms / resistance
What is a Megohmmeter used to measure?
Measures very high resistance
What does a Wattmeter measure?
Electrical power
What are the four factors to consider before taking a measurement with a meter?
Electrical measurement
Energized or de-energized
Value expected
Polarity
True or false:
Downscale deflection does not cause damage.
False
1 mil is how many inches?
1 mil is 1/1000th of an inch
When attaching a meter to a circuit (Voltmeter) it will be …
In parallel
An ammeter will be connected…
In series
When attaching an Ohmmeter it will be
In series
Zero out ohmmeter by
Touching cords.
Can an Ohmmeter be connected on a live circuit?
Never
