Learning Module A1 Flashcards
What does EMF stand for?
Electric Motive Force
What are the five different quantities in electricity?
- Charge
- Current
- Voltage
- Resistance
- Power
These quantities are fundamental in the study of electricity.
What symbol is used to represent the quantity of charge?
Q
Q stands for the quantity of electric charge.
What is the unit of charge represented by the charge on 6.24 x 10^18 electrons?
Coulomb
Named after Charles Augustin Coulomb.
What is the abbreviation for the unit of electric charge?
C
C stands for coulomb.
What does the term ‘current’ refer to in electricity?
The rate of flow of charge
Current is essential for discussing electric circuits.
What symbol is used to represent electric current?
I
The symbol I is likely derived from the word intensity.
What is the unit of current and who is it named after?
Ampere, named after Andre Ampere
The unit is critical for measuring the flow of electric charge.
What is the abbreviation for the unit of current?
A
A stands for ampere.
How is 1 ampere defined in terms of coulombs?
1 A = 1 C/sec
This means 1 coulomb of charge crosses a point in 1 second.
How many electrons correspond to 1 ampere?
6.24 × 10^18 electrons per second
This highlights the large number of electrons constituting a current.
What is needed to move an electron from the negative terminal to the positive terminal?
Voltage
This refers to the energy needed to overcome the forces acting on the electron.
What kind of energy is given to an electron when it is moved against a force?
Potential energy
The energy is given as work is done against the electric forces.
What is the term for the potential energy difference between two points in an electric circuit?
Potential difference
It represents the energy required to move a charge between those points.
What is the abbreviation for potential difference?
PD
What is the unit of potential difference?
Volt
The volt is named after Alessandro Volta.
What is the relationship between joules and coulombs in defining a volt?
1 V = 1 J/C
If it takes 3 joules of energy to move 1 coulomb of charge, what is the potential difference?
3 volts
What happens to potential energy within an energy source and the rest of the circuit?
Potential rise in the source, potential drop in the circuit.
What is the term for the push supplied by the source to the electrons?
Electromotive force (emf)
This push is analogous to compressing a spring.
What is referred to as the voltage drop?
Potential drop occurring in the circuit.
What is the common abbreviation used for both potential difference and electromotive force?
E
What is the abbreviation for resistance?
R
What opposes the flow of electric current in a circuit?
Resistance
Similar to how friction opposes motion.
True or False: If nothing opposed the flow of current, it would eventually stop.
False
What is the electrical unit of resistance?
The ohm
Named after Georg Simon Ohm
What is the abbreviation for the unit of resistance?
The Greek letter omega, 0
How is 1 ohm defined in terms of voltage and current?
1 volt causes a current of 1 ampere to flow
1 Ω = 1 V/A
If 1 volt is applied across a device and ½ of an ampere flows, what is the resistance?
2 ohms
If 3 volts are applied across a device and 1 ampere flows, what is the resistance?
3 ohms
What is the definition of power in physics?
The rate at which work is done or energy is transferred
What is the abbreviation for power?
P
What is the unit of power?
The watt
Who is the watt named after?
James Watt
What is the definition of one watt?
1 joule per second
What is the formula relating power, voltage, and current?
1 W = 1 V x 1 A
What is the definition of energy?
Energy is the ability to do work.
Work is done when an applied force moves an object through a distance in the direction of the applied force.
What is the relationship between work and energy?
When work is done on an object, the object is given energy equal to the work done on it.
The symbol for energy is W, which is also the symbol for work.
In a mechanical sense, how is work defined?
Work is defined as force times distance.
How does an object transfer energy?
An object can transfer energy to another object by doing work on it.
What happens when a force is applied to lift a volume of water?
The volume of water gains energy equal to the work done on it.
What is power?
Power is the rate of doing work.
What is the relationship between energy, power, and time?
Energy = power x time.
In electrical units, how is power calculated?
Power is equal to volts times amperes.
How is energy calculated in electrical units?
Energy is equal to volts times amperes times time.
What do electrical supply authorities charge customers for?
They charge customers for energy, not power.
What type of meter is used to measure energy consumption?
Kilowatt-hour meters.
What is the unit of energy?
The unit of energy is the kilowatt hour.
What is the unit of power?
The unit of power is the watt.
What is the unit of time used in electrical measurements?
The unit of time is the hour.
What is horsepower referring to on a motor?
Output
Input on a motor is defined as?
Power Draw
What is Ohm’s law?
The current in an electric circuit is proportional to the applied voltage and inversely proportional to the resistance of the circuit.
Mathematically, Ohm’s law is expressed as I = E ÷ R.
What is Watt’s law?
The power transformed in an electric circuit is equal to the product of the applied voltage times the circuit current.
Mathematically, Watt’s law is expressed as P = E × I.
How many equations can be derived from Ohm’s law and Watt’s law?
Ten equations can be generated by using transposition and substitution.
These equations allow calculation of any two electrical quantities if the other two are known.
Why is it important to calculate voltage, current, resistance, and power?
It is not always practical or possible to measure all four quantities directly.
Knowing how to calculate them allows for better understanding and troubleshooting of electrical circuits.
What happens to the resistance of a light bulb when it is hot?
The resistance increases
However, when cold, the resistance is significantly lower at about 10 ohms.
What are loads in electrical circuits?
Devices that convert electrical energy to other forms of energy.
Purely resistive devices convert energy mainly to heat, and sometimes to light.
How does current affect the heating of a resistive device?
An increase in current leads to more collisions between electrons and molecules, resulting in increased energy transfer and heating.
This means the device becomes warmer as the rate of electron flow increases.
What is power in the context of electrical circuits?
The rate of doing work or the rate of energy transfer.
Power is directly proportional to both voltage and current.
What happens to power if either voltage or current increases?
Power increases.
This is because power is directly proportional to both voltage and current.
Fill in the blank: Power is directly proportional to both _______ and _______.
voltage, current
What does Ohm’s law state about the relationship between current and voltage?
The current in a circuit is directly proportional to the applied voltage
If the voltage in a circuit doubles, what happens to the current?
The current also doubles
What is the effect on power when both voltage and current double?
The power increases by four times
What is the formula for power in relation to resistance and current?
P = I² x R
What are superconductors?
Conductors that have no resistance
What is I^2 R loss?
Power loss in conductors due to resistance
How is electrical energy converted in a conductor with resistance?
Some electrical energy is converted to heat
What is the formula to calculate IR loss in conductors?
P = I² x R
What could happen if power loss in conductors is reduced?
Fewer generating stations would be needed, reducing pollution
What is a resistor?
An electrical component that introduces a specified amount of resistance into a circuit
What is the primary function of resistors in circuits?
To limit current, provide a change in voltage, or produce heat
How are resistors rated?
According to their resistance value and wattage
What happens to the physical dimensions of a resistor as its wattage rating increases?
The physical dimensions increase
What does a tolerance rating indicate for resistors?
What the nominal resistance value may vary by
What materials are commonly used in wire-wound resistors?
Nichrome wire, covered with ceramic or hard plastic
What are the three main classes of fixed resistors?
Wire-wound resistor, film resistor, carbon-composition resistor
What types of resistors exist?
Fixed, variable, adjustable
What is a photo resistor?
A light-sensitive resistor whose resistance drops sharply when exposed to light
What are the characteristics of wire-wound resistors?
Used for higher wattage ratings; made from nichrome wire
Fill in the blank: Resistors are identified by ______ bands.
colour
True or False: Fixed resistors can vary in resistance.
False
What type of resistor is often used for high wattage ratings?
Wire-wound resistor
What is the typical resistance range for wire-wound resistors?
From a fraction of an ohm to thousands of ohms
What are DIP packages?
Dual in-line packages for certain types of resistors
What is a film resistor?
Coated in carbon compound or metallic oxide, accurate and can replace wire round resistors
What is a carbon resistor?
Cheap is to make. Maximum of 2 watts of current depending on size.
What is a fuse?
An overcurrent device designed to open the circuit if the current exceeds its rating
A fuse protects the circuit by breaking it before damage occurs.
What is the primary function of a fuse?
To break the circuit before damage is done
How is a fuse designed in relation to the electric circuit?
To be the weakest link in the circuit
What does a fuse consist of?
An element or link housed in a protective enclosure
Describe the operation of a fuse.
A heat-sensitive device with a metal alloy element that melts open when the current exceeds its rating
What causes the fuse element to heat up?
The higher resistance of the fuse element compared to the conductors it protects
What is the relationship between the time it takes for a fuse to open and the magnitude of the current?
The time is inversely proportional to the magnitude of the current
What happens to a fuse during a heavy fault current?
It opens almost instantly
What are some characteristics that can vary among different types of fuses?
- Voltage and current ratings
- Response characteristics
- Current-limiting capabilities
- Shapes and sizes
What are time-delay fuses?
Fuses that take more time to melt and open under certain conditions
Where are fuses commonly used?
- Homes
- Offices
- Industry
- Automobiles
- Ships
- Electronic equipment
Fill in the blank: A fuse does not instantly open when the current exceeds its rated value; it responds to the heat generated by the flow of current through it, causing the link to _______.
[melt open]
True or False: The higher the amperage and voltage rating of a fuse, the smaller and shorter it will be.
False
What happens to fuse on an overload current?
Burns slower than on a fault current
What are the two types of cartridge fuses mentioned?
Ferrule type and knife-blade type
Knife-blade type is used on fuses rated above 60 A.
What is the main difference in length between fuses rated for 600 V and those rated for 250 V?
Fuses rated for 600 V will be longer than fuses rated for 250 V.
What are plug fuses also known as?
Screw-in fuse or Edison-base fuse
They were common in wiring installations in homes but have largely been replaced by circuit breakers.
In what applications are plug fuses still commonly used?
Domestic ranges and older installations.
What serious shortcoming did plug fuses have in the past?
A fuse of much higher ampere rating could replace a smaller fuse.
What do current regulations require for plug fuses?
Designed to prevent a higher ampere fuse from replacing a smaller fuse.
What is a renewable link fuse?
A fuse that can be used repeatedly because the element can be replaced.
What is a disadvantage of renewable link fuses?
It is possible to install a larger link, compromising the integrity of the installation.
Fill in the blank: The knife blade end of a fuse is used on fuses rated above _______.
60 A
True or False: Plug fuses are no longer used in any applications.
False
Breaker trip mechanisms?
Magnetic quick activation and Thermal requiring time to activate
What is the primary purpose of conductor insulation?
To prevent unwanted flow of electrical current, such as ground faults, short circuits, or electric shock.
What is dielectric strength?
The ability of a material to resist breakdown under voltage.
What happens if insulation is stressed by too great a voltage?
It may break down and conduct.
How does temperature affect insulation life?
For every 10°C beyond normal rating, the insulation life is reduced by one-half.
What factors should be considered for the location of insulation?
Moisture, toxic elements, and conditions of use, and potential mechanical damage.
What is magnet wire used for?
Used in meter coils, small transformers, relays, motor windings, and other electromagnetic applications.
What are the key properties of the insulation used on magnet wire?
- Moisture- and chemical-resistant
- Non-corrosive to copper
- High in heat transferability
- Not too costly
What is varnished cambric?
Insulating tape made from impregnated cloth.
Fill in the blank: The insulation must have a voltage rating suitable for the _______.
[circuit application]
What is hygroscopic material?
A material that absorbs moisture.
An example is cambric, which is hygroscopic but less so when impregnated with varnish.
What is the dielectric strength of properly varnished cambric?
About 1000 volts per mil.
This strength is significantly increased when varnished.
What happens if cambric insulation is stretched too tightly?
The varnish film may be broken or weakened, spoiling its insulating capacity.
What are the minimum and maximum temperature suitability of rubber formulations?
Some are suitable for -55°C minimum, others for +75°C maximum.
What are the two main characteristics of thermoplastic materials?
They soften when heated and harden as they cool.
They also exhibit cold flow under pressure.
What is the maximum operation voltage for PVC insulation according to the Code?
600 V AC.
What does the T type identification letter for PVC indicate?
Suitable for dry locations only.
What does the TW type identification letter for PVC indicate?
Suitable for use in wet and dry locations.
What does the TWU type identification letter for PVC indicate?
Suitable for direct burial in the ground.
At what temperature does PVC begin to soften and flow?
150°C.
What is the maximum conductor temperature allowed for PVC?
60°C.
What is cross-linked polyethylene identified as?
XLPE or X LINK.
What are the properties of cross-linked polyethylene?
Combines excellent electrical properties of thermoplastic polyethylene with thermal properties of thermosetting material.
What is a key characteristic of minerals used for insulation?
They are very stable and capable of operation at high temperatures.
Cable made from Magnesium Oxide and used in high heat or potentially explosive atmospheres?
Pyrotenax Cable
What voltage range does the CEC define as low voltage?
31 V to 1000 V
What is the maximum voltage that some control circuits, such as those for motors, may operate at?
600 V
What are conductors for control circuits required to be?
Properly rated for the voltage value
What is classified as extra-low voltage?
Operating at 30 volts or less
What is the common wire size for bell wire used in extra-low voltage circuits?
AWG sizes No. 16 and smaller
What are Class 2 circuits as described by the CEC?
Low energy control circuits and methods of wiring
Name three common examples of Class 2 circuits.
- Circuits supplying relays
- Doorbells
- Buzzers
What is a cable assembly?
A cable assembly consists of multiple single-conductors
List the commonly used types of cables in wiring installations.
- Non-metallic sheathed cable
- Armoured cable
- Aluminum-sheathed cable
- Mineral-insulated cable
- Neutral supported cable
- Service entrance cable
- Flexible cord or cable
What does CEC stand for in the context of wiring installations?
Canadian Electrical Code
What is the most commonly used cable for dwelling units?
Non-metallic sheathed cable (NMSC)
What are the three categories of non-metallic sheathed cables based on installation conditions?
- Type NMD90
- Type NMW
- Type NMWU
What does the ‘D’ in Type NMD90 signify?
Dry or damp locations
What does the ‘W’ in Type NMW signify?
Wet locations
What does the ‘U’ in Type NMWU signify?
Underground
What are the limitations of Non-metallic sheathed cable?
Limited to circuits not exceeding 300 V and used in combustible (wood frame) construction
What is the temperature rating for Type NMD90 cable?
90°C
What is a warning issued by the Electrical Equipment Manufacturers Association of Canada (EEMAC) regarding non-metallic coverings of electric cables?
Non-metallic coverings can burn, transmit fire, emit toxic acid gases, and corrode nearby metal
Burning non-metallic coverings may generate dense smoke and cause damage to sensitive instruments.
What type of cable contains an interlocking metal armour sheath?
Armoured cable (AC)
Armoured cable is designed to protect insulated conductors from mechanical abuse.
What is another name for Armoured Cable (AC)?
BX
The term BX has been traditionally used for armoured cables.
Fill in the blank: Type AC armoured cable is limited to _______.
dry wiring locations only
What does Type ACWU armoured cable contain that makes it suitable for wet or underground installations?
A thermoplastic covering over the armour
What are the typical voltage ratings for TECK cable?
600 V, 1 kV, or 5 kV
What temperature can types of TECK cable be suitable for down to?
-40°C
What are the two finishes available for Aluminum-sheathed cable (ASC)?
Smooth or corrugated finish
The corrugated type is commonly referred to as corflex.
What additional layer does Aluminum-sheathed cable (ASC) have for adaptability?
A PVC jacket over the outer sheath
ASC Cable typical Voltage rating?
600V to 5000V
Another name for LWMI Cable?
Pyrotenax.
What is NSC Cable?
Neutral supported cable.
What is triplex NSC used for?
Single-phase, three-wire, 120/240 V overhead distribution
Triplex NSC stands for Neutral Supported Cable.
What does quadruplex NSC refer to?
Three-phase, four-wire feeders
Quadruplex NSC is used in more complex electrical distribution systems.
What type of cable is Range and dryer cable?
Type DRT
It consists of a twisted assembly of four coloured insulated conductors including ground.
What is the maximum voltage rating of Range and dryer cable?
300 V maximum
This cable comes in lengths up to 2 m and has a permanently attached plug.
What common sizes are available for Range and dryer cable?
- No. 10
- No. 8
- No. 6
- No. 4 AWG
These sizes refer to the gauge of copper wire.
What is the maximum voltage rating of heater cord?
300 V
Sizes range from No. 18 to No. 14 AWG.
What are common types of heater cord listed in the CEC?
- HPD
- HPN
- SHJO
These types indicate different specifications for heater cords.
What types of general-service cords are available for outdoor use?
- Type SJOW (300 V)
- Type SOW (600 V)
These types are specifically rated for outdoor conditions.
1 coulomb
Corflex
What is FCC Cable?
Flat Conductor Cable
What unit is line drop measured in?
Volts.
