week #2 Flashcards
What are the 2 basic types of electrical sources?
A: direct current / alternating current
Which of the 2 different types of electrical sources is considered unidirectional?
direct current
Which type of electrical source does the battery that starts our cars use? What is the most common car battery Voltage
DC, 12 V
The receptacles and lights in our homes and schools uses which type of electrical source? What is the Voltage used?
AC 120V
What is electricity?
Electricity is the flow of negatively charged electrons
What is the basic building block of the universe known as?
The Atom
What is a substance that cannot be chemically divided into two or more simpler substances?
Element
Elements are composed from what?
Atoms
What are the three principle parts of an atom?
Proton Neutrons and electrons
What is the nucleus of the atom composed of
Protons and Neutrons
Does the nucleus of an atom have a negative charge?
No the charge is positive
What does the basic law of physics state about charges?
Opposite charges attract and like charges repel
Will atoms with the same electrical charge repel each other?
Yes
The electrons located in the outer shell of an atom are known as what type of electrons?
Valence electrons
Good conductors generally contain how many valance electrons?
1 to 3
Semi-conductors generally contain how many valance electrons?
4
Insulators are known to be very poor conductors of electricity, how many valance electrons do elements known as insulators contain?
7-8
List 2 examples of good insulators.
Wood and glass, rubber plastic
List 2 examples of conductors?
Copper, and aluminum.
Electrical wire uses both a good conductor and a good insulator. Can you explain why?
The good conductor allows for the ease of flow of electrons and is wrapped with an insulator to prevent any electrical leakage—for example dead shorts, ground shorts, and electrocution.
A quantity measurement of 6,250,000,000,000,000,000 is known to as what?
Coulomb
What is the standard name used to describe the amount of electricity flowing through a circuit?
Ampere
If 15 coulombs of electricity flow past a point in the wire in one second, how many amps are there? Make sure you indicate with the symbol!
15 A
When calculating for ampacity using algebraic formulas, our text book uses what letter to indicate ampacity?
I
When we use the word current when talking about electricity, what are we referring to?
Ampacity
The potential difference between two points in an electrical circuit is a measurement of what?
Voltage
What is the letter symbol use to represent a quantity of voltage on our Multi meters?
V
1 volt is the amount of potential necessary to cause 1 coulomb to produce 1 joule of work. How
many volts would we have if we if we created 120 joules of work? Write your answer with the letter symbol to indicate voltage.
120 V
EMF or electromotive force and potential difference is two ways of describing voltage. When
using a water system as a comparison, what is another commonly accepted way to describe
voltage?
Electrical pressure
When calculating Voltage using algebraic formulas, our textbook uses what letter to indicate
Voltage or Electromotive force?
E
What is the unit of resistance to current flow called?
An ohm
What is the symbol used to represent the quantity of resistance (R) on our Multi meters?
Greek letter Omega.
When calculating algebraic formulas what letter is used to represent resistance?
(R)
What is the word used to describe the amount of power being used in a circuit?
Watt
What is the symbol used to describe Watts?
W
When calculating algebraic formulas what letter is used to represent Power or Watts?
P
Can we measure Power or Wattage with our Multi meters?
No
What is the formula used for calculating Power or Wattage?
P = E x I
Electricity frequency is measured in Hertz (Hz), what is the standard frequency for AC voltage
used in our homes in Canada?
60Hz
When talking about electricity what is considered a load?
Anything that uses electricity to do work
What is the difference between Electron flow theory, and conventional flow theory, and what
type of power supply does it apply to?
Electron flow is from negative to positive, and vice versa for conventional, applies to DC only
Even though today we use both electron flow Theory and conventional flow theory. Which of
the two is considered to be more correct?
Electron
1HP = W
746 Watts
746 Watts = ?ft-lb/s
550 ft-lb/s
1 watt = HP
0.00134 HP
0.00134 HP = ?BTU/hr
3.412 BTU/hr
An elevator must lift a load of 5000lbs to a height of 75 ft. in 30 s. How much horse power is
required?
A=5000x75=375000 then 375000/30=12500 Then 12500/550=22.73 HP
A water heater contains 200L of water in the tank, Water weighs 1 kg per litre. The present
temp of the water is 30 degrees C. The water temp must be raised to 80 degrees C in one hour.
How much power will be required to raise the water to the desired temperature?
Step 1 - 200x1=200kg Step 2 – 80-30=50 degree Step 3. 200x50x4200=42000000 step#4
42000000/3600=11666.67W
How many Milli seconds are there in 1 minute?
1 minute = 60 seconds so
simply move the decimal to the right 3 spaces so 60000 milli seconds in one
minute.
How many Mega seconds are there in a minute?
Simply move your decimal
point 6 spaces to the left. So .000060 Mega seconds
Distance (length (L), height (H), and width (W) is measured in?
Meters (M)
Mass (m) is measured in?
Grams (G)
Time (t) is measured in?
Seconds (S)
Speed, Velocity (v) is measured in?
Meters per second (M/S)
Can we use the table found in Figures 2-22, and 2-23 to convert all of the Metric base units of measurement listed in question 53?
Yes absolutely
Is the long line on the symbol for a battery considered positive or negative?
Long line is positive
What is created when you take 2 unlike metals and insert them into an acid, alkaline, or
salt solution?
A voltaic cell
What is a very simple example of a voltaic cell?
Potato, copper, and aluminum wire
inserted into a potato, or even a lemon.
What determines the amount of voltage created by a cell?
The material from which it’s made
What is the difference between a primary cell, and a secondary cell?
Primary cell can’t be recharged, and secondary can
Is a lead acid cell considered a Primary or a secondary cell?
Secondary
Lead acid is the most common type of battery used in our cars, most gas powered cars use 12 VDC. According to Figure 13-6 how many lead acid cells would need to be connected in series to obtain a minimum of 12 volts?
6
Do batteries have 2 different voltage ratings?
Yes, one when there is a load on the
battery, and another when there is no load on the battery.
Batteries are considered to be under load when?
Current is flowing
A battery such as the lead acid uses what tool to measure its specific gravity?
Hydrometer
Can you use a Hydrometer to determine the state of charge of a lead acid cell battery,
and why?
Yes, if water is 1.0 and a fully charged battery is 1.28, the range is now .28 so
.14 would be considered half charged
In your words describe the discharge cycle of a Secondary cell such as the lead acid
battery?
When a load is connected to the battery the battery discharges its stored energy. Essentially the electrons from the electrolyte flow as the molecules (lead sulfate) in the electrolyte chemically attaching themselves to either the positive, or
negative dissimilar metal plates (depending on their chemical composition and positive
or negative charges). As the electrons move through the load in this case a light bulb the electrolyte turns from acid back into water.
Can car batteries freeze in the winter, potentially damaging them?
yes
In your words describe the charging cycle of a lead acid Battery?
Put a DC power supply
to the battery, needs to be about 2 volts higher than the listed voltage so around 14 volts. This produces hydrogen at the negative plate, and oxygen at the positive plate
causing the lead sulphate back into the water creating sulphuric (battery) acid again.
The two main sources of electricity?
Alternators for DC, and generators for AC
Another small source for generating DC electricity other than batteries is what?
Solar
How does solar power work
Stack to semiconductors on top of each
other, one that is positive, and the other that is negative. The photons from the sun or other light sources, pass through the semiconductor transferring electrons into the semiconductor allow current to flow from the negative to the positive….basically like the
+/- of a battery.
What is the name of another device that uses 2 different materials, that when heated they create electricity?
Thermal couple
Different types of thermocouples are created by different materials and their type
indicated by a letter as shown in figure 13-37. What is main difference between each
type?
Temperature tolerances or ranges.
What is 2 or more thermocouples that are connected in series known as?
Thermopile
