Electrical Flashcards
Use a _____ when you work in a damp or wet location
Dry wooden platform to sit or stand on
If a person forms a closed circuit through which current can flow, and the power source supplies a voltage causing current to flow, a voltage of _____ or less, the person will be killed
115 volt
Place ___ between you and the wood surface you’re working on
Rubber matting or other non conductive material
What kind of tools and flashlight should you use when working on exposed electrical equipment
Insulated tools Nonmetallic flashlight
Electric shock may be avoided by using safety equipment such as ____
Deck coverings and rubber gloves
Prevents electrical shock to anyone who may touch bare, energized, or ungrounded circuits
Insulated deck covering
Rubber floor matting must conform to
Military specification Mil-M-15562
Gives approved deck coverings for every space
NSTM, chapter 634, table 634-1
Repair defective matting by ____
Covering the affected area with a new piece of matting
Foreign substances on matting contaminate or impair its ____
Dielectric properties
The dielectric properties of matting can be impaired or destroyed by ____
Oil, embedded metal chips, cracks, holes, or other defects
The primary feature discriminating one class of glove from another
Maximum safe voltage of the glove which is determined by its thickness
Class 0 gloves have a maximum safe voltage of _____ and labeled ____
1000 volts Red
A class 1 glove has a maximum safe voltage of _____ and is labeled _____
7500 volts White
A class II glove has a maximum safe voltage of ____ and is labeled _____
17500 volts Yellow
A class III glove has a maximum safe voltage of _____ and is labeled _____
26500 volts Green
To inspect rubber gloves for tears, snags, punctures, or leaks that are not obvious _____
Hold the glove downward, grasp the glove cuff, and flip the glove upward to trap air inside the glove. Roll or fold the cuff to seal the trapped air inside, then squeeze the inflated glove and inspect it for damage
For additional info on rubber gloves, refer to ______
NSTM, chapter 300
Who must approve work to be done on energized circuits
CO
Coat metallic hand tools with _____
Plastisol or cover them with two layers of rubber or vinyl plastic tape, half-lapped
When working on live or hot circuits, you must be ____
Supervised and aware of the danger involved
Refer to _____ for instructions on the use of plastisol
NSTM, chapter 631
If you don’t have enough time to apply plastisol or tape ____
Cover the tool handles and their exposed parts with cambric sleeving, synthetic resin flexible tubing, or suitable insulation
In a shipboard real ungrounded system, the factors of _____ must be considered
Resistance (R) Capacitance (C)
Insulation resistance of a system is periodically measured with ______
500-volt DC megger
If you are using a megger to check for ground in the system, and you get a reading of _____, you can conclude that no low resistance ground exists
50000 ohms resistance
System capacitance exists in parallel with ____
Resistance
The main reason we ground power tools and equipment is for ____
Safety
Proper grounding can prevent lethal shocks by ____
Limiting voltages due to line surges or unintentional contact with higher voltage lines
When using a multimeter to check continuity of the ground conductor from the tool case to the dummy receptacle, you should make sure the reading is ____
Less than 1 ohm
Isolated receptacle circuits are limited to _____ in length
1500 feet
Isolated receptacle circuits limit ground leakage currents to _____
10mA
Definition of electricity
Force that causes electrons to move from one atom to another
Electrons have a ____ charge
Negative
Protons have a _____ charge
Positive
Most atoms have an equal number of ______
Electrons and protons
Electrons in the _____ can become free of their orbit
Outer band
As free electrons move from one atom to the next an ____ is produced
Electric current
Materials that permit many electrons to move freely
Conductors
Materials that allow only a few electrons to move freely
Insulators
An atom with an equal number of electrons and protons
Electrically neutral
Act like a conductor when external force is applied in one direction and act like an insulator when the external force is applied in the opposite direction
Semiconductor
Caused by an absence or excess of electrons
Positive or negative charge
Atom that has gained or has an excess of electrons
Negative charge
An atom that has lost or has an absence of electrons
Positive charge
The force of attraction or repulsion depends on the strength of the charged bodies and the distance between them
Coulomb’s law of charges
The flow of free electrons in a conductor from one atom to the next atom in the same general direction is referred to as ____
Current
Current is designated by the symbol _____
I
The number of electrons that pass through a cross section of a conductor in one second determines ____
Current
Current is measured in _____
Amperes or amps
Unit abbreviation for amps
A
In mathematical equations amps is represented by
I
6.28 x 10^18 electrons moving through a cross section of a conductor in one second equals _____
One amp
Conventional current flow states that current flows from _____ to _____
Positive to negative
Electron flow states that current flows from ____ to ____
Negative to positive
Continuous flow of electrons in one direction
Direct current
When the electrons flow first in one direction, then reverse direction and flow the opposite direction
Alternating current
The force required to make electrons flow through a conductor is called ____
Difference in potential, electromotive force (emf), or voltage
Unit of measurement for voltage
Volts
Unit abbreviation for volts
V
In mathematical equations volts is represented by _____
E or V
Voltage is usually indicated symbolically on an engineering drawing with a ______
Battery symbol
On the symbol for a battery, two lines indicate ______
The terminals of a battery
The two lines on a battery symbol, the longer line represents _____
Positive terminal
Six methods of producing voltage
Friction Pressure Heat Light Chemical action Magnetism
Produces voltage by rubbing certain materials together
Friction
Produces voltage by squeezing crystals of certain substances
Pressure (piezoelectricity)
Produces voltage by heating the joint where two unlike metals are joined
Heat (thermoelectricity)
Produces voltage by light striking photosensitive substances
Light (photo electricity)
Produces voltage by chemical reaction in a battery cell
Chemical action
Produces voltage in a conductor when the conductor moves through a magnetic field, or a magnetic field moves through a conductor, so that the magnetic lines of force of the field are cut
Magnetism
All voltage sources share the characteristic of ______
An excess of electrons at one terminal and a shortage of electrons at the other terminal
Material impedes the flow of electrical current to some extent. This characteristic is called ____
Resistance
Resistance in a conductor increases with _____, or a decrease of ______
Length Cross section
Unit of measurement for resistance
Ohms
Unit abbreviation for ohms
Omega
In mathematical equations ohms is represented by ____
R
Resistance is usually indicated symbolically on an electrical drawing by
An unfilled rectangle or a zig zag line
Current varies directly with voltage and inversely with resistance
Ohm’s law
The rate at which work is done
Power
Power is represented by the symbol ____
P
Power is represented in _____
Watts
Watts are represented by the symbol ____
W
The rate work is done in a circuit when one amp flows with one volt applied
Watt
Electrical equipment is rated in ____
Watts
An indication of the rate at which electrical equipment converts electrical energy into other forms of energy
Wattage rating
Consists of a voltage source with a positive and a negative terminal, some type of load providing resistance, and a conductor allowing electrons to flow between the voltage source and the load, with a complete path for current to flow
Simple electrical circuit
Has only one path of current flow
Series circuit
More than one path of flow for electrical current
Parallel circuit
Circuit in which the electricity has found an alternative path to return to the source without going through an appropriate load
Short circuit
Conductor that is intentionally grounded to earth at the power supply
Grounded conductor
This conductor is called the neutral wire and is identified with the color white or gray
Grounded conductor
Occurs when there is an accidental path of low resistance between the electrical conductor and earthen ground
Ground fault
Three basic properties of components used in electronic circuits
Resistance, capacitance, inductance
The property of a component to oppose the flow of electrical current through itself
Resistance
The property of a component to oppose any change in voltage across its terminals, by storing and releasing energy in an internal electric field
Capacitance
The property of a component to oppose any change in current through itself, by storing and releasing energy in a magnetic field surrounding itself
Inductance
Components that are used to control the amount of current flowing in a circuit
Resistor
Also known as a condenser, is a device that stores energy in an electric field, by accumulating an internal imbalance of electric charge
Capacitor
Consists of two conducting plates separated by an insulating material called dielectric
Capacitor
Directly proportional to the surface areas of the plates, and is inversely proportional to the separation between the plates
Capacitance
Standard unit of measure for capacitance
FARAD
Unit abbreviation for a FARAD
F
An electronic component that stores energy in the form of a magnetic field and consists of a wire loop or coil
Inductor
As current flows through the wire, a magnetic field is generated; this is known as ____
Electromagnetism
Increasing current flowing through the wire causes voltage to be produced by the magnetic field, which opposes the change in current; this is known as _____
Inductance
Directly proportional to the number of turns in the coil, also depends on the radius of the coil and on the type of material around which the coil is wound
Inductance
Standard unit of measure for inductance
HENRY
Unit abbreviation for HENRY
H
Schematic symbol for HENRY
L
The force where objects are attracted or repelled to one another, due to the motion of electric charges
Magnetism
Invisible magnetic lines of force, leave the north pole and enter the south pole of a magnet
Flux
Continuous, always forming complete loops, never crossing one another, and passing through all materials both magnetic and non-magnetic
Magnetic lines of force
Space around a magnet in which these lines of force may be detected
Magnetic field
Produced whenever there is an electrical charge in motion
Magnetic field
Production of a magnetic field by current flowing in a conductor
Electromagnetism
Produces an electromotive force (emf) or voltage, which in turn produces a current
Magnetic field
Process of generating current in a conductor by placing the conductor in a changing magnetic field
Induction
For electromagnetic induction to take place, the conductor must be _____
Perpendicular to the magnetic lines of force, or else no voltage will be induced
Determined by the direction of the lines of force and by the direction the wire is moving in the field
Direction that the induced current flows
A coil of wire spun in a magnetic field at a constant rate will produce ___
AC electricity
Most versatile meter
Multimeter
Measures current
Ammeter
Measures the potential difference (voltage) between two points
Voltmeter
Measures resistance
Ohmmeter
Comprised of a display, function switch, connection terminals, and range button
Fluke digital multimeter
Useful in locating defective circuits and components during corrective maintenance
Resistance measurements
When measuring voltage, connect the meter leads in _____ the voltage to be tested
Parallel (or across)
Measuring resistance, k = reading x _____
1000
Resistance measurement, M = reading x _____
1000000
Device that measures current
Ammeter
The multimeter must be wired in _____ with the loads in order to monitor the current
Series
Has a hook that is clamped around a conductor and detects the rising and falling magnetic field
Clamp-on ammeter
The Amprobe AC/DC 600A can test up to ____
600 amps AC and DC
To check circuit current flow, the circuit must be ____
Energized
Two instruments most commonly used to measure resistance of a circuit
Ohmmeter and the megohmmeter
Cannot be used for measuring resistance of multimillions of ohms such as in conductor insulation
Ordinary ohmmeter
Used to measure very high resistance values such as those found in cable insulation and motor and transformer windings
Megohmmeter
Uses a relatively high voltage (500V - 1000V) in order to determine resistance in mega ohms
Megger
Which meter provides the most adequate test for insulation breakdown
Megohmmeter
What is the advantage of clamp on ammeter versus the multimeter type of ammeter
Not limited by test leads
Term used for an electrical current that moves only in one direction
Direct current
Occurs when the polarity and output voltage from a power source never change direction
DC
Converts mechanical energy into electrical energy
Charging circuit
Typical charging circuit consists of ____
Battery, alternator, voltage regulator
Provides for general, detail, special, low level, and emergency illumination
Lighting circuit
Used to alert the crew whenever there is a deviation from the engine’s normal operating parameters
Engine alarm circuit
The equipment used to steer a ship or boat on the operator’s desired course
Steering circuit
_____ pressure sensor output is normally around 30mV and directly proportional to the pressure sensor input power or excitation
Millivolt
____ power supplies are suggested for use with millivolt sensors
Regulated
_____ pressure sensor output is normally 0 - 5 VDC or 0 - 10 VDC, and the output of the sensor is not normally a direct function of excitation
Volt
This pressure sensor is not as susceptible to electrical noise and can be used in more industrial environments
Volt pressure sensor
4 - 20 mA pressure sensor
Pressure transmitter
Pressure transmitter commonly found in applications where the lead wire must be ____ or more
1000 feet
Used to monitor the speed of rotation for components
Speed sensor
Consist of a coil wrapped around a magnet and located near a gear wheel
Magnetic speed sensor
Frequently used as switches or controls for mechanical devices such as valves
Solenoids
Consists of a wire coil and a movable plunger that rests next to the coil
Solenoid
Device that usually moves or controls equipment to give a change in position or direction
Actuator
Two common methods for isolating a problem within a system
Half-split and section-by-section
The half-split method works best on ____
Large systems
The section-by-section method works best on ___
A smaller system such as a small portion of a large system
What two types of checks are performed for troubleshooting
Visual and operational
How can components be isolated from wiring and other components
Tripping a breaker, opening a switch, or disconnecting the component
Why is additional test equipment needed when testing pressure and temperature switches or sensors
To simulate pressure or temperature
Hazards posed by batteries
Electrical shock, acid burns, explosion, release of hazardous gases
This is produced while charging batteries
Hydrogen sulfide
Lower the charging rate as soon as the battery begins to gas or the temperature reaches ____
125*F
Keep the temperature of the battery compartment below ____
96*F
Make no repairs to battery when ____
Current is flowing
In a battery, always pour ___ slowly into ____, never the other way around
Acid into water
If eyes contact acid, flush them for how long
Minimum 15 minutes
Do not add acid of greater specific gravity than ___ to a battery
1.350
Do not store sulfuric acid where
Freezing temperatures are possible
Keep the electrolyte level ____ above the tops of the separators
3/8”
Never allow a battery to stand in a completely discharged condition for more than ____
24 hours
Never operate a battery above _____
125*F
Device that transforms chemical energy into electrical energy via an electrochemical process or chemical reaction that produces electrons
Battery
Consists of two or more cells assembled in a common container and connected together to function as a source of electrical power
Battery
Consists of two strips of dissimilar metals, or electrodes, placed in a container with a solution known as electrolyte, a nonmetallic conductor
Simple cell
The conductors by which the current leaves or returns to the electrolyte
Electrodes
Solution that acts upon the electrodes and provide a path for electron flow (internal resistance)
Electrolyte
Commonly comprised of sulfuric acid and distilled water, but may be salt, an acid, or an alkaline solution
Electrolyte
Energy is derived from an essentially irreversible electrochemical reaction; cannot be efficiently recharged; and is discarded following discharge
Primary cell battery
Primary cell battery also called
Dry cell
Secondary cell battery is also called
Wet cell
The electrodes and the electrolyte are altered by the chemical action that takes place when the cell delivers current. These cells may be restored to their original condition by forcing an electric current through them in the direction opposite to that of discharge
Secondary cell battery
Secondary cell batteries are commonly known as
Storage batteries
Voltage source that uses chemical action to produce a voltage
Battery
Batteries connected in parallel provide higher
Current capacity
Batteries connected in series provide
A higher voltage
Used to remove corrosion and dirt from battery terminals and cable clamps
Battery brush
Side terminal brush
Used to clean corrosion from side post batteries
Used to remove the battery terminal clamp without damaging the battery post
Battery terminal puller
Used to clean and spread battery terminal cables
Battery terminal spreader and cleaner
Used to add water or electrolyte to the battery
Battery filler
The electrolyte level shall be inspected how often
Once a week or more
First step in installing a battery
Determine the polarity of terminals
Ratio of the weight of a certain volume of liquid to the weight of the same volume of water
Specific gravity
Specific gravity of electrolyte in a battery gradually ____ on discharge
Decreases
Glass barrel fitted with a rubber nozzle at one end which may be dipped into the electrolyte of a cell without risking damage to the separators
Battery hydrometer
For most batteries the float should be graduated to cover specific gravities in the range of ____
1.100 - 1.300
In a new battery, the specific gravity should read
1.260 - 1.300
Fully charged battery hydrometer reading
1.260
75% charged battery hydrometer reading
1.250
50% charged battery hydrometer reading
1.220
25% charged battery hydrometer reading
1.190
Discharged battery hydrometer reading
1.130
Normal temperature to which specific gravity readings are corrected
80*F
How many points to add to each reading for each 10*F above 80*F
4
Fast and easy-to-use method for testing battery charge condition and for testing the freezing point of glycol based antifreeze
Refractometer
The glycol and battery tester is available in two models
7084VP for testing in Fahrenheit, and 7064VP for testing in Celsius
The coolant reading is on the ____, battery charge is on the _____ (refractometer)
Right, left
Rate at which electron flow is forced into the battery
Charging rate of a battery
Safest charging rate
Below 10 amperes
Four types of charges that may be given to a storage battery
Initial, normal, equalizing/boost, floating
A normal charge is complete when the specific gravity of the pilot cell, corrected for temperature, is within ___ of the specific gravity obtained on the previous charge
5 points
Randomly selected cells located in the center of each battery system used to monitor temperature and specific gravity
Pilot cells
For additional information on the selection of pilot cells, see
NSTM, chapter 313, 313-2.3.3, numbering batteries
During a normal charging procedure, check the temperature and specific gravity how often
Every hour
During a normal charging procedure, do not allow the temperature of the electrolyte of exceed
52*C, 125*F
Extended normal charge at the finishing rate
Equalizing/boost charge
When the battery is held at a specific voltage that is well below its gassing point until fully charged
Floating charge
Typical float charge for a 12-volt, lead acid battery
13.1 volts
Best method to check battery condition
Battery load tester, also called battery capacity test
Measures the current output and performance of the battery under full load
Battery load test
Evaluates the batteries ability to supply sufficient current to the standby supply or other electronic device
Battery load tester
To test, battery terminal voltage must be
12.60V or greater
Number of amperes a lead-acid battery at 0*F (-17*C) can deliver for 30 seconds and maintain for at least 1.2 volts per cell (7.2 volts for a 12 volt battery)
Cold cranking amperage
Tools used to diagnose engine start systems
Battery analyzers
Use conductance technology instead of load test
Battery analyzers
Slender rod or filament of drawn metal
Wire
Measures diameter of conductor
Wire gauge
What to consider when choosing a wire gauge
The distance it will run and the amperage it will be expected to carry
First step in making a splice
Stripping or removing insulation from the wire
Strippers will only strip how much insulation at a time
3/4”
Most common connectors used for splicing or connecting electrical wires
Wire nut, split bolt splice, pre-insulated terminal lug, pre-insulated splice
Device commonly used to replace the rattail joint splice, should be considered temporary in marine applications
Wire nut
Housed in plastic insulating material, place two stripped conductors in and twist
Wire nut
Often used to join large conductors and can be used to replace the knotted tap joint
Split bolt splice
Small diameter copper wires are terminated with solderless ____
Pre-insulated terminal lug
Used to join small copper wire AWG sizes no. 26 through no. 10
Pre-insulated splices
Yellow (bright) terminal lug or splice insulation is used on sizes
26 - 24
Red terminal lug or splice insulation is used on sizes
22 - 20, 18
Blue terminal lug or splice insulation is used on sizes
16 - 14
Yellow (dull) terminal lug or splice insulation is used on sizes
12 - 10
Final step in completing a splice or connection
Placing insulation over the splice
Five common insulators used for splicing
Heat shrinkable tubing, rubber tape, friction tape, electrical tape, electrical coating
Most common form of insulator used for terminals
Heat shrinkable tubing
Heat shrinkable tubing shrinks how much when heated
One half its original diameter
When using heat shrinkable tubing, hold the heat source how far away
4 - 5 inches
When using heat shrinkable tubing, apply heat of how much for how long
275*F to 300*F for 30 seconds
After heating heat shrinkable tubing, let it cool for how long before handling
30 seconds
Splicing compound used when the original compound is rubber
Rubber tape
Cotton cloth that has been treated with a sticky rubber compound, is used to restore the protective covering and provide some electrical insulation
Friction tape
Commonly used to repair and protect bare wires, can withstand higher voltages for a given thickness
Electrical tape
Fast drying sealant and bonding agent recommended for splices wrapped with tape
Electrical coating
Electrical flow in which the current flows first in one direction until the voltage reaches the peak desired value, then reverses its flow until the peak desired value is reached in the opposite direction
Alternating current
AC generator converts mechanical energy into electrical energy by utilizing the principle of
Electromagnetic induction
Generator converts energy by
Producing currents in conductors rotated in a magnetic field
Graphic representation for AC
Sine wave
A sine wave can represent
Current or voltage
A sine wave moves through a rotation of
360 degrees
A sine wave moving through one complete rotation is known as
A cycle
Unit of measurement for cycles per second
Hertz (Hz)
Consists of a permanent magnet, an armature, slip rings, brushes, and a conductor loop
Elementary AC generator
After the loop has rotated ____, the current direction switches
180 degrees
Collect the current from the slip rings and transfer the current via an external circuit
Conducting brushes
Number of cycles per second made by voltage induced in the armature
Frequency of the generator
Fast drying sealant and bonding agent recommended for splices wrapped with tape
Electrical coating
Electrical flow in which the current flows first in one direction until the voltage reaches the peak desired value, then reverses its flow until the peak desired value is reached in the opposite direction
Alternating current
AC generator converts mechanical energy into electrical energy by utilizing the principle of
Electromagnetic induction
Generator converts energy by
Producing currents in conductors rotated in a magnetic field
Graphic representation for AC
Sine wave
A sine wave can represent
Current or voltage
A sine wave moves through a rotation of
360 degrees
A sine wave moving through one complete rotation is known as
A cycle
Unit of measurement for cycles per second
Hertz (Hz)
Consists of a permanent magnet, an armature, slip rings, brushes, and a conductor loop
Elementary AC generator
After the loop has rotated ____, the current direction switches
180 degrees
Collect the current from the slip rings and transfer the current via an external circuit
Conducting brushes
The frequency is the same as
The number of rotations per second
AC circuit has two characteristics
Voltage and current
When two waveforms are in step with each other
In phase
When the circuit is a resistive circuit, the voltage and the current will be
In phase
When the circuit contains an inductive load, the relationship will be
Forced out of phase
When two waveforms are out of phase, the relationship between the two is called
Lead or lag
Phase differences are expressed in
Degrees
AC is divided into
Single phase, and three phase types
Used for small electrical demands as found in the home
Single phase power
Made up of a number of windings (coiled conductor) connected in series, forming a single circuit
Single phase generator
This voltage is represented by a singe waveform
Single phase power
Continuous series of three overlapping AC cycles and is used where large blocks of power are required such as in commercial applications and industrial plants
Three phase power
Has three single phase windings which create three separate circuits
Three phase AC generator
Three phase AC generator windings are ____ out of phase with the voltages in the other two windings
120 degrees
Three phase power is represented by
Three waveforms
One of the most common loads on any electrical system
Electric motor
Device which converts electrical energy (current) into mechanical work (motion)
Motor
Typical motors are powered by
120V, 240V, or 480V supplies
Comprised of a fixed outer portion called the stator, and a revolving inert portion called a rotor
AC motor
Made up of a hollow cylinder or core with slots
Stator
The type of motor is determined by
The number of windings and their configuration
Two types of rotors
Cage rotor, wound rotor
Have a laminated cylindrical core with parallel slots in the outside circumference to hold the windings in place
Rotor
This rotor has an uninsulated bar winding
Cage rotor
This rotor has a two layer distributed winding with preformed coils
Wound rotor
AC motors are classified by
The type of AC power they use to operate
Require additional power in order to produce a rotating magnetic field
Single phase motors
Incoming power produces a rotating magnetic current on its own, allowing this motor to be self starting
Three phase motor
AC motors can be divided into the following types
Series, synchronous, and induction
Have field poles wired in series with the rotor
Series type motors
Needs brushes to ride on a communicator, a pair of rings attached to the shaft of the rotor, to provide the connection between the poles and the rotor
Series type motor
A series motor is also called
A universal rotor because it can be hooked up to AC or DC voltage
Specifically designed to maintain constant speed with the rotor, synchronous to the rotating field
Synchronous motor
This motor requires modification to be self starting
Synchronous motor
Have a rotor turned by induction from the stator
Induction motor
Most commonly used AC motor
Induction motor
1HP =
746 Watts
Voltage on a motor must be maintained ____ for reliable operation
Plus or minus 10%
Motor must always maintain ___ of rated frequency to prevent damage
Plus or minus 5%
Insulation temperatures are represented in
Degrees Celsius
To convert Celsius to Fahrenheit
x 1.8 + 32
To convert Fahrenheit to Celsius
-32 x .555
Motor windings can be tested for the following faults
Open winding, shorted winding, ground
Motor windings should be tested when
Immediately following shutdown when the motor windings are still hot and dry
Result of a burned wire in the winding or a break somewhere in the winding that prevents the current from completing the circuit
Open winding
Motor with this will not start
Open winding
Result of two windings making contact
Shorted winding
Will eventually result in an open winding
Shorted winding
Result of an electrical conductor in contact, either directly or indirectly, with the motor frame or the metal shell of the unit
Ground
A ground is either
One of low resistance or high resistance
Indicated when fuses blow repeatedly and the motor fails to start
Low resistance ground
Indicated by an occasional blown fuse, but more often by the opening of the overload protector
High resistance ground
This fault can lead to a serious shock hazard
Ground
When testing motor windings for ground using a megohmmeter disconnect
The motor leads from each other to ensure the readings are indicated only one winding at a time
Mounted externally to the engine and are used to circulate the coolant through the water jacket
Engine heaters
Occurs when a gas or liquid is heated by some external means, causing the lighter heated gas or liquid to rise
Thermo-siphon
This process can be used to move heated air or water through a system without externally powered pumps or fans
Thermo-siphon
Under normal conditions, all the coolant in the engine will pass through the heater how often
Three or four times an hour
Two main benefits of using an engine heater
Easier starts and reduced engine wear
Two pieces of metal that touch to make a circuit and separate to break the circuit
Contacts
Switches are classified according to
The arrangement of their contacts
Set of contacts that belong to a single circuit
Pole
One of two or more positions that the switch can adopt
Throw
Actuated by gas or liquid pressure in a piston, diaphragm, or bellows, and converts pressure to mechanical force
Pressure switch
Protective device inserted in series with a circuit containing a metal that will melt or break when current is increased beyond a specific value for a definite period of time
Fuse
Three types of fuses
Plug, ribbon, knife
Designed to break the circuit and stop the current flow when the current exceeds a predetermined value
Circuit breaker
Commonly used in place of a fuse and may eliminate the need for a switch
Circuit breaker
Two common types of circuit breakers
Thermal, magnetic
Seven common types of drawings
Pictoral Isometric Block Single-line Terminal Schematic Wiring
Simplest of all diagrams
Pictoral
Shows a picture or sketch of the components of a specific system and the wiring between these components
Pictoral
This type of diagram provides a means to recognize the physical appearance of each component and its interconnections with the other components of the system
Pictoral
Shows the sequence in which the components are connected without regard to their physical location, how the wiring is marked, or how the wiring is routed
Pictoral diagram
Purpose of this diagram is to assist you in locating a component within a system
Isometric diagram
Shows the major components of a system and the interconnections of these components, and is often used with accompanying text material
Block diagram
Used basically for the same purpose as the block diagram. When used with text material, it provides you with a basic understanding of the components and their functions in a system
Single-line diagram
Two major differences between single line diagram and block diagram
Single line uses symbols rather than labeled blocks, and all components are show on a single line with no interconnections
Useful when connecting wires to terminal boards, relays, switches, or other components of a circuit
Terminal diagram
Two types of terminal diagrams
Terminal board diagram Relay terminal diagram
Most commonly used diagrams
Schematic and wiring
Emphasize connections between elements of a circuit or system
Wiring diagram
Use horizontal and vertical lines to represent wires
Wiring diagram
Use simplified pictorials that clearly resemble circuit/system components
Wiring diagram
Place equipment and wiring on drawing to approximate actual physical location in real circuit
Wiring diagram
Emphasize flow of system
Schematic diagram
Use horizontal and vertical lines to show system flow
Schematic diagram
Use symbols that indicate function of equipment, but the symbols do not look like the actual equipment
Schematic diagram
Drawing layout is done to show the flow of the system as it functions, not the physical layout of the equipment
Schematic diagram
Uses graphic symbols to show both the electrical components and the functional organization of a circuit
Schematic diagram
This diagram should be used to determine the location where the trouble in the circuit could be when a malfunction occurs
Schematic diagram
Shows all wiring, connectors, terminal boards, and electrical or electronic components of a circuit
Wiring diagram
May identify wire-by-wire number or color code
Wiring diagram
This diagram should be used to troubleshoot and repair electrical or electronic circuits
Wiring diagram
Can be used to determine where to make the voltage or resistance checks in the circuit
Circuit-wiring diagram
To read electrical diagrams and schematics properly, what must first be understood
The condition or state of each component
To associate the proper relay with the contacts that it operates, each relay is assigned
A specific number and/or letter combination
The position of one internal switch will affect the position of another
Ganged switches
Ganged switches are shown symbolically by
Connecting them with a dashed line
Used to indicate a mechanical interlock between two circuit components
Dashed line
Wires that are connected are usually depicted on a diagram with what at the point where the wires join
Dot
Wires that cross but do not join are depicted by
A hump
Never operate any personal electronic equipment without the authorization of who
XO EO
What level of shock from a 60-Hz AC system can be fatal if it lasts for one second or more
100 milliamperes (0.1 A)
What firefighting agent is not recommended for electrical fires because it causes corrosion of electrical and electronic components
Potassium bicarbonate (PKP)
When at sea, what is more fatal and damaging to both personnel and the ship itself than damage from battle
Fire
