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
