Electrical Flashcards
This component of matter is the smallest part that matter can be divided into without changing its makeup.
Molecules
What are molecules made up of?
Atoms
What are atoms made up of?
- Protons
- Neutrons
- Electrons
The protons and neutrons are located in the nucleus of the atom.
What parts of an atom are located in the nucleus of the atom?
Protons and neutrons
Which parts of an atom are located outside of the nucleus?
Electrons
What components of an atom exert a force known as an electric charge?
Protons and electrons.
Protons are positively charged, and electrons are negatively charged.
Which component of an atom has no charge?
Neutrons
Neutron = neutral.
True or false: Normal atoms have the same number protons and electrons and are neutral in charge.
True
If an object has more protons than electrons, it is ____________ charged.
Positively
If an object has more electrons than protons, it is ____________ charged.
Negatively
What are free electrons?
Electrons that are loosely bonded around the nucleus and can readily be knocked loose.
These are conductors.
____________ is a useful form of energy derived from unbalanced electrical charges in materials.
Electricity
When electricity does not move, it is called:
Static electricity
The Law of Electric charges states that like charges ___________ (attract/repel) on another.
repel
The Law of Electric Charges states that unlike charges ____________ (attract/repel) one another.
attract
What are the two aspects of electromagnetism?
- Magnetism
- Electricity
This is one of the fundamental natural forces.
______________ is a physical phenomenon caused by electron movement.
Magnetism
This movement causes a magnetic field around the magnet.
What causes a magentic field to develop around a material?
Electron movement
True or false: A strong magnetic field occurs when a formation of aligned atoms occurs in a material.
True
This type of magnet is caused by spinning electrons in the atoms that make up the material the magent is formed out of.
A permanent magnet
What causes the magnetic property of an electromagnet?
Electrons moving through a coil of wire wound around a core material.
Why is the magnetic field the strongest at the north and south poles of a bar magnet?
This is where the magnetic lines of flux are densest.
The more lines of flux, the greater the magentism.
What happens to the end of an iron bar as it is brought close to a magnet?
The end of the iron nearest the magnet assumes the opposite polarity of the magnet.
This causes the iron bar to become attacted to the magnet.
Remember that opposite charges attract while like poles repel
Placing a compass near a wire carrying an electric current causes the comapss needle to deflect at right angles to that wire. The direction this deflection depends upon:
the direction (polarity) of current flow
True or false: Moving electrically charged particles create magentic fields.
True
The greater the volume (amperage), the greater the magnetic field.
True or false: Magentic fields attract or repel moving charged particles.
True
This depends on the charge of the particles.
True or false: Moving magentic fields near charged particles causes current to flow.
True
- When current passes through a conductor, the closer to the conductor, the ____________ the magnetic field.
- Why is this,
- Stronger
- This is because the lines of flux are more concentrated closer to the conductor.
How is EMF generated?
By passing a conductor through a magentic field (or vis versa).
This is voltage.
What is the current called that is caused by passing a conductor through a magentic field (or vis versa).
induced current
What effect does inserting a soft iron core into the windings of an electromagnet have?
It increases the strength of the electromagnet
The permeability of the iron allows the lines of flux to establish more easily, resulting in a greater density of flux lines ⟶ more flux = stronger magnet.
The ease with which a material can be magnetized by a solenoid is a measure of its:
permeability.
This physical characteristic is an indication of how well a material can “conduct” or “permit” magnetic field lines to pass through it.
This type of material exhibits low resistance to current flow.
A conductor
1 to 3 valence electrons.
This type of material exhibits high resistance to current flow.
An insulator
5 to 8 valence electrons.
What type of atoms have virtually no free electrons on their outer rings, and the outer rings have their full count of electrons.
Insulators.
5 to 8 valence electrons.
This type of material is neither a good conductor nor a good insulator.
semi-conductors
4 valence electrons
What are the two most common semi-conductor materials?
- silicon
- Germanium
How can the conductivity of semi-conductors be increased?
By doping them with impurities.
This changes the number of free electrons in the valence shell of the atom.
What are the two common types of semi-conductor materials?
- n-type
- p-type
What is a transistor?
An electrical switch
When voltage is applied to the gate, the semiconductor will pass voltage and current through it.
What is needed in order for a transistor to conduct electricity?
A voltage applied to the gate (trigger)
When voltage is applied to the gate of transisitor, this semiconductor will act like a:
conductor
When voltage is removed from the gate of a transistor, this semiconductor will act like a:
insulator
This type of electrical current flow is always in the same direction.
direct current (DC)
Which type of current flow has a fixed polarity: AC or DC?
DC
Direct Current
Which type of current flow has a changing polarity: AC or DC?
AC
Alternating Current
What the instantaneous polarity of an AC circuit?
The polarity of the circuit at that instant in time
As a conductor rotates through magnetic lines of flux, when does maximum induced voltage occur?
When the conductor is travelling at right angles to the lines of flux
In this case, at points 3 and 9.
As a conductor rotates through magentic lines of flux, when is there no induced voltage in the conductors?
When the conductor is travelling parallel to the lines of flux.
In this case, at points 0 and 6.
In an AC circuit, what is one cycle?
0V ⟶ Max (+) V ⟶ 0V ⟶ Max (-) V ⟶ 0V
This is a complete sine wave, or one cycle.
In electrical circuits, the ________ is the number of cylcles an alternating current generates per second.
frequency
In North America, how many AC cycles happen in one second?
60
This is the frequency, which is measured in Hertz (Hz).
What is frequency measured in?
In Hertz (Hz)
As it pertains to electricity, ________ indicates the relationship in time (in degrees of rotation) between current and voltage.
phase
________-phase refers to a single voltage (rising and falling potential) that creates a potential difference between only two conductors.
Single-phase
________-phase refers to three different voltages (rising and falling potential) that interact to produce potential differences between the three conductors.
Three-phase
True or false: Automobile alternators generate three-phase AC current, recitify this to a DC current, then regulate it to a standard DC output.
True
For an electrical current to flow, there must be a potential difference between two points. This potential difference is called:
voltage (EMF)
The mathematical symbol for voltage is E.
What is the unit of measurement for voltage?
volts
The mathematical symbol for volts is E.
With electricity, one ________ causes one ampere to flow through a resistance of one ohm.
One volt
This electrical property is similar to pressure in hydraulic circuits.
voltage
It’s the force that pushes electric charges through a conductor.
With electricity, ________ is the rate of flow of electrons in an electrical circuit.
amperage (amps)
The mathematical symbol for amps is I.
With electricity, one ________ flows when an EMF of one volt is applied across a resistance of one ohm.
one amp
This electrical property is similar to flow in hydraulic circuits.
Amperage
The mathematical symbol for amps is I.
It is a measure of the rate at which electric charge passes a point in the circuit.
Current flow determines what two things on a motor?
- speed
- power output
True or false: The amperage is governed by the available EMF and the resistive elements in a circuit.
True
This relationship is defiined in Ohm’s Law.
In electrical circuits, ________ is done when a force overcomes an opposing resitance.
work
Work always requires a distance component.
In electrical circuits, ________ is having the potential to do work.
energy
Joules and calories.
In electrical circuits, ________ is the rate at which work is done.
power
Power has a time component.
Electrical power is the rate of doing work measured in:
watts
1 hp = 746 watts
With electricity, one amp per second flowing under the potential difference of one volt is equal to:
one watt of power
The mathematical symbol for watts is P.
What three things are requred for an electrical circuit to work?
- power source
- conductors
- load
When two lamps are connected end to end, or in tandem, this would be considered ________ electrical circuit.
series
When current flows through a divided path in an electrical circuit, this is said to be a(n) ________ circuit.
parallel
This intrinsic physical characteristic of a material is it’s opposition to the flow of current.
Resistance
In electrical circuits, an object with one ________ allows one amp to flow when a potential difference of one volt is applied across it.
ohm
The mathematical symbol for ohms is R.
True or false: The symbol for resistance value is Ω.
True
What effect does current flowing through a reistor have on the voltage across the resistor?
It causes a voltage drop.
The voltage drop is the electrical potential that is used up overcoming the resistance, which generates waste heat in the form of consumed power (I²R losses).
What factors affect the resistance of a circuit?
MALT
M = material
A = area
L = length
T = temperature
The conductivity ratings of materials are compared to what material?
Silver at a rating of 100.
What is the best conductor material?
Silver
The cross-sectional area of a conductor is measured in:
circular-mills
The use of circular mils simplifies the calculation of the cross-sectional area of wire because the wire’s diameter is commonly given in mils (thousandths of an inch).
When the area of a conductor doubles, the resistance:
Halves
Area ↑ = Resistance ↓
They are inversely proportional.
What happens to the resistance of a conductor if the length of the conductor doubles?
The resistance doubles.
Length ↑ = Resistance ↑
The are directly proportional.
What effect does temperature have on the resistance of materials?
Temperature ↑ = Resistance ↑
This electrical device is used to introduce a known amount of resistance into a circuit.
Resistors
Resistors have wattage ratings.
True or false: Since an electric current flowing through a resistance generates heat, resistors have wattage ratings.
True
What three factors affect the inductance of a component?
- Material
- Frequency
- # of turns (length)
Inductance is measured in Henry’s (L)
What is inductance?
The tendency of an electrical circuit to oppose a change in the electric current flowing through it.
What does an inductor do in an AC circuit?
oppose the flow of current
This is called inductive reactance (XL).
What is inductive reactance measured in?
ohms (Ω)
What two thing are inductive reactance of an AC circuit directly proportional to?
- Amount of inductance
- frequency
This simplified electrical component consists of two conductors separated by an insulator.
A capacitor
Capacitors store electrical charge
This electrical component stored electrical charge.
Capacitors
What are three common metals that are considered magnetic.
- nickel
- cobalt
- iron
What material property does the gate in a transistor have?
semiconductor
What type of electrical device causes inductance in a circuit?
A coiled conductor
What effect does amperage have on a magnetic field?
The greater the amperage, the greater the magnetic field.
True or false: Being in the vacinity of a strong electric arc can cause serious ultraviolet burns.
True
A welding flash is an example of this type of damage.
Until the voltage of a power line is verified, a safe clearance of ____ ft must be maintained.
22 ft (7m)
True or false: Amps are what kill you.
True
- What can happen if an electrical disconnect is opened while under load?
- Why is this?
- Arc flash
- The switch doesn’t move fast enough to reliably extinguish the arc that develops across the open contacts.
With electrical diconnects, horsepower ratings over ____ hp are most vulnerable to arcing.
50 hp
How much space is required to be left clear in front of electrical equipment by the CEC?
1m to the front of the component
CEC = Canadian Electrical Code
How should a person orientate themselves when opening a disconnect switch (3 steps)?
- Stand on the same side as the switch (if possible)
- Turn your head away from the switch
- Throw the switch with your left hand.
Based off of this module, and nothing else.
As it pertains to electrical equipment, what are line lugs?
The hot (energized) connections on a disconnect switch or circuit breaker.
These are usually located on the top of the disconnect.
Where are the line lugs usually located on an electrical disconnect switch or circuit breaker?
On the top of the component.
True or false: Line lugs are not always at the top of the disconnect or breaker in combination switches even through code states incoming feed is to be at the top.
True
True or false: It is fine to open a breaker without first shutting off the motor that it feeds.
False
Always shut off the motor before opeing the breaker.
When troubleshooting or working on an electrical panel or component, what needs to be done after the panel/component has been LOTO?
Test starts the panel/component
Always check the line lugs with a multimeter before touching them.
What does a conductor cable with a burnt jacket indicate?
Damage to the conductor
This damage can be caused by heat, chemicals, moisture ingression, UV, dirt/debris on the cable.
What do discolouration on the motor starter lugs indicate?
Heat damage
Usually from loose connections.
Why is it important for broken conduits or electrical fittings to be repaired immediately?
These fittings can be the ground “wire”
Ensuring good continuity of the grounding circuit is critical to the safety of personnel.
When it comes to electricity, what is a brown-out?
A low-voltage condition
Brown-outs are situations where voltage has dropped to below normal conditions. This could be caused by the supply company, or some other issue within the facility.
True or false: A tripping circuit breaker is usually a symptom of the problem, not the problem itself.
True
Usually the problem is with the equipment that the circuit breaker is protecting.
What function do fuses serve in an electrical circuit?
Overload and short circuit protection
They do this by limiting the maximum current flow to a safe level during a short circuit failure or heavy sustained overload.
What are the two types of fuses used in electrical circuits?
- fast acting
- time delay (dual element)
What type of fuse is a dual element fuse?
A time delay fuse
These are used for overload protection on motors or other components where an overload condition can be allowed for a short amount of time.
What are the two fuse link elements found in a time delay fuse?
- thermally delayed fuseable link
- instant blowing link
Which part of a time delay fuse protects the circuit from a sustained low level overload?
The thermally delayed fuseable link
Which part of a time delay element protects the circuit from a high current fault?
instant blowing link
What types of electrical components are usually protected by time delay fuses?
motors or similar loads
These loads have high inrush currents during start-up.
This type of fuse is said to be current limiting.
Time delay fuses
What effect does moisture or dirt have on the insulation around a conductor?
Reduces the resistance of the insulation.
What type of current limiting device is filled with sand to suppress the arc that occurs when the fuse blows?
HRC fuses
What construction componet of an HRC fuse allows the fuse to clear 200,000 to 300,000 amps?
Sand
The pure sand supresses the arc.
What does HRC stand for on HRC fuses?
high rupturing capacity fuses
What type of fuse is used to prevent over amperage of an electrical motor?
Time delay fuses
What component of a motor is a fuse or breaker designed to emulate and protect?
The windings
These work on emulating the temperature of the motor winding that they protect.
What are the two types of thermal overload relays?
- bimetallic
- melting alloy
This type of overload relay uses a heater element to detect the amount of current flowing through the circuit, with excessive current causing the element to bend and trip the relay.
bimetallic overload relays
True or false: Bimetallic relays can be adjusted for either manual or automatic reset.
True
This type of overload relay uses a pot filled with low-temperature melting alloy fastened to the current carrying bar to sense the motor windings.
Melting alloy overload relays
What happens when a melting alloy overload trips?
The alloy melts, causing the ratchet wheel to release the trip mechanism.
Which type of overload relay has a ratchet wheel holding the trip mechanism closed?
Metling alloy overload relays.
With both AC and DC circuits, when measure an unknown voltage, always start with the ________ voltage setting.
highest
If there is no reading, proceed to lower the voltage setting.
True or false: Voltage readings are taken with the circuit de-energized.
False
The circuit must be live to take voltage readings.
True or false: Voltage readings differing in excess of ±3% begin to affect motor performance.
False
Voltage readings differing by ±5% beings to affect motor performance.
How is a volt meter connected to the circuit for testing?
In parallel to the component being tested.
How is an ammeter connected to the circuit for testing?
In series with the component being tested.
What fault is created when an ammeter is connected in parallel to a component?
A short circuit condition.
When testing with an ohmmeter, should the circuit be energized or de-energized?
De-energized.
Ohmmeters can also create a short circuit condition.
With an ohmmeter, what are megohms are used for testing?
high-resistance circuits and resistor and for checking motor windings to ground.
What is a megohmmeter used for testing?
The integrity of insulation.
This meter detects voltage leakage to ground.
With a two-wire plus ground circuit, what are the following wire colour codes?
1. Hot wire
2. Neutral wire
3. Ground wire
- Hot wire (line) = black
- Neutral wire = white
- Ground wire = bare copper or green
With a three-wire supply circuit , what are the following wire colour codes?
1. Hot wire #1
2. Hot wire #2
3. Neutral wire
4. Ground wire
- Hot wire #1 = red
- Hot wire #2 = black
- Neutral wire = white
- Ground wire = bare copper or green
This is a 3-wire Edison circuit.
After an electric motor has been installed into place, why is it a good idea to test start the motor uncoupled?
Ensure the motor is rotating in the correct direction.
True or false: If the grease that is expelled from the vent port on an electric motor looks discoloured, continue to pump grease in until clean grease exits the vent port.
True
What information on a motor nameplate designates the multiplier that can be applied to the horsepower to indicate the amount it can be overloaded?
SF or service factor
These are 1.00, 1.15, and 1.25.
Why is it important to keep the exterior of motors free from dirt and debris build up?
Cooling
Dirt and debris act like a thermal blanket, reducing the motors ability to cool itself.
When listening to a motor, what does a gravelly noise coming from the motor bearing indicate?
Bearing damage
When listening to a motor, what does a squealing noise coming from the motor bearing indicate?
Too tight of bearing clearances or lack of lubrication
After greasing a motor, why is it a good idea to let it run for 5 to 10 minutes before reinstalling the grease plug?
Allow excess grease to escape.
What does duty indicate on a motor nameplate?
If the motor can run continuously or intermittenly
What does Fr. No indicate on a motor nameplate?
The frame number
This is the size and mounting orientation of the motor, including mounting holes size and location, shaft centreheight, etc.
True or false: Stop buttons in an electrical circuit are usually normally closed.
True
What function do electrical interlocks provide in a circuit?
The prevent electrical equipment from operating out of sequence.
Which type of breaker is designed to protect against severe and light overload conditions?
thermal/magnetic
