Electricity - Basic Navy Training Courses
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¶ U.S. GOVERNMENT PRINTING OFFICE; 1945 - 618779
How Well Do You
1. The smallest particles making up an atom are _____________.
2. The particle of matter having a positive charge is called a
3. The particle of matter having a negative charge
is called a _____________.
4. What small particles unite
to form molecules?
1. How do like charges act on each other?
2. How do unlike
charges act on each other?
3. When electrons are removed from
an object, the object has a _____________ charge.
are electrons and not protons removed by friction?
5. The force
which causes electrons to flow is called _____________.
6. Static electricity is _____________ electrons.
Current electricity is _____________ electrons.
does a condenser do with its electrical charge?
ELECTRICITY IN MOTION - CURRENT
1. How does a current flow through a wire?
2. What is the
electrical unit of quantity?
3. What is the unit of measure of
4. What two things control the strength of
5. Why are some substances good conductors?
Why are some substances good insulators?
7. If the potential
of any given circuit is increased, the current is always _____________.
8. If "the resistance of any given circuit is increased, the current
is always _____________.
9. What four things affect the
resistance of a conductor?
THE ELECTRICAL CIRCUIT
1. Identify each symbol in the circuit diagram below. Refer to the
table in figure 15 for your answers.
2. Why are dirty or loose connections classified as "opens"?
3. In making any type of connection, what is the most important
thing to remember?
4. Why are fuses made of metals which melt
at a low temperature?
5. What are some common causes of short
6. Why are no intentional grounds used on regular Navy
1. What does emf mean?
2. What four kinds of energy can be
converted into electrical energy?
3. What are the two most common
sources of electrical power?
4. What is an ion?
can't primary cells be recharged?
6. What is the principal advantage
of secondary cells?
1. Solve for the unknown value in each of the circuits in the following
2. A lamp has 2 amperes of current through its 30 ohms of resistance.
What current will
flow if the resistance is increased
to 60 ohms?
3. A certain lamp has 50 ohms of resistance and
is built to carry 2.4 amperes. Will the
(a) 110 v. (b) 220 v.?
4. What two things control current in
1. Does an empty lamp socket have force?
2. Is any work done
by an open circuit?
3. Is any power consumed by an open circuit?
4. A generator supplies a 72 ampere load at 600 volts. What is the
power consumed by
the load in watts? In kilowatts?
5. A 50 hp motor draws 80 amperes at 600 volts. What is
the power input? Power output
in watts? Efficiency?
6. The prime mover of a generator furnishes 37 hp to the generator.
The electrical load on
the generator is 70 amperes
at 440 volts. What is the power input in watts? Power
output in watts? Efficiency?
7. A power line has a drop of 18
volts in transmitting a load of 75 amperes. How much
power is lost in this line?
8. What is the resistance of the
line in problem 7?
9. If a line consumes 650 watts in transmitting
55 amperes, what is the potential drop?
10. How much power will
be consumed by a 75 hp motor operating at 80 percent efficiency?
In hp? In watts? In kilowatts?
THE SERIES CIRCUIT
1. Work out the answers for each unknown in the practice circuits
in the following drawing.
2. Three heating resistances are connected in series. Each has a
resistance of 20 ohms
and a current of 10 amperes.
What is the voltage drop across (a) each resistance,
(b) the total circuit?
3. What is the power consumed (a) in each
unit, (b) in the total circuit of problem 2?
4. Two 25 watt lamps
are connected in series on a 240 volt line. What is the current
through each lamp?
5. What is the total voltage drop of four
resistors connected in series, if each resistor has
50 ohms resistance and 4 amperes of current?
1. Work out the answers for each unknown in the practice circuits
in the following drawing.
2. Four motors are paralleled on a 120 volt line. What is the total
line current if each
motor draws 2.5 amperes?
3. What is the total resistance of one 10 ohm resistor, one 20 ohm
resistor, and one
30 ohm resistor if they are
connected in parallel?
4. Two loads are connected in parallel
on a 220 volt line. The first draws 25 amperes and
the second draws 41 amperes. What is the total current? What is the
5. In a 120 volt parallel circuit there are
four devices. One requires 1/2 ampere, another
1/4 ampere, another 1-1/4 amperes, and the fourth 3 amperes. What is
6. What is
the resistance of each device in problem 5? What is the total resistance?
1. Work out the answers for each unknown in the practice circuits
in the following drawing.
2. How would you connect one switch to control two lamps?
3. Eight lamps are paralleled across one circuit. How would you
connect one fuse so as
to protect every lamp?
1. All magnets have at least _____________ poles.
two methods of producing an artificial magnet.
3. What two things
does a vector show about a force?
4. What are the three important
facts about a magnetic field?
5. Like magnetic poles _____________
6. Unlike magnetic poles _____________ each other.
7. Flux can choose either an air or an iron path. Which does it
8. Where does a compass point true north?
10. About how much variation would a compass have
if it were located at the mouth of
the Mississippi River?
11. What is deviation?
12. If you
should break an ordinary magnet into 5 pieces, how many poles would
13. A piece of iron has magnetic lines passing through
it. A pattern of its field with iron
filings shows that many of the lines do not go through the iron - instead
through the, air. Why?
14. Permanent magnets have a high _____________.
1. Is the direction of flux correctly labeled for the electromagnets
in the following drawing?
2. Which of these coils is the strongest?
A has 22 turns and 5 amperes.
B has 37 turns and 3 amperes.
C has 17 turns and 9 amperes.
3. How can you increase a coil's
strength without changing the construction?
1. What two factors control the direction of an induced emf?
2. What three factors control the strength of an induced emf?
3. How many circuits are necessary for mutual induction?
4. How many circuits are necessary to produce self-induction?
5. Will steady d.c. produce a continuous self-induction? Why?
6. State Lenz's law in simple language.
7. How may the voltage
of self-induction be dangerous around a motor?
8. In what one
way does pulsating d.c. differ from regular d.c.?
9. In what
two ways does a.c. differ from regular d.c.?
1. Name the two essential circuits of a generator. Briefly describe
the parts of each.
2. When is the induced voltage of a coil
3. When is the induced voltage of a rotating coil at its
4. Is a.c. or d.c. produced inside a rotating
5. How is d.c. obtained from a rotating coil ?
6. Adding coils to an armature does what to the. d.c. produced?
7. What connection is used between coils of an armature to produce
a high and
8. Why is a drum
winding superior to a ring winding?
9. Distinguish between the
stator and the rotor of an alternator.
10. Why are a-c machines
designed opposite to d-c machines?
1. How does a d-c motor differ from a d-c generator in construction?
2. Motor action results from the reaction between two _____________.
3. What is motor action in a generator?
4. What is counter-emf
in a motor?
5. What effect does counter-emf have on armature
6. What happens to the amount of counter-emf if the
motor is slowed down?
7. What effect does decreased counter-emf
have on the amount of current?
8. What is the principle function
of a starter?
9. What are the two methods of reversing a motor?
10. What is standard Navy practice for reversing a motor?
1. What is the name of the only d-c motor which will run on a.c.?
2. What is the polarity of the secondary if the primary is north?
3. Do a-c coils have a fixed polarity?
4. What does
5. What are the units for measuring phase?
6. What is the meaning of "out-of-phase?"
7. Does any
mechanical part of a stator move?
8. What does move in a rotating
9. Does the squirrel cage rotor have any electrical
connection to a source of supply?
10. How does current get in
the squirrel cage rotor?
11. The squirrel cage rotor is what
kind of a circuit?
12. Does a wound rotor have an electrical
connection to a source of supply?
13. How does current get in
the wound rotor?
14. How is a synchronous rotor energized?
15. What is "magnetic lock?"
16. Name the three types
of single phase motors.
17. What two methods are used to split
single phase into two phases?
1. What are the two outstanding characteristics of a.c.?
2. An a.c. has a maximum value, of 25 amperes. What is its effective
3. How does resistance affect the phase of a current?
4. How does inductive reactance affect the phase of a current?
5. How does capacitive reactance affect the phase of a current?
6. How could you reduce the total reactance of an inductive
7. A circuit contains 18 ohms of capacitive reactance,
12 ohms of inductive reactance
and 8 ohms of resistance.
(a) What is the total reactance? (b) What is the impedance?
(c) Does the current lag or lead?
1. What four quantities are measured in an electrical circuit?
2. What are the three current effects used in meters?
3. Name the meters which can be used on a.c. or d.c.
Which meter can be used on d.c. only?
5. Properly connect the
meters and loads shown above in their circuits.
1. In thermionic emission, why do electrons shoot off the metal
2. Why is the air removed from a vacuum tube?
3. Why is the cathode negative regardless of battery connection?
4. Why does current never flow from plate to cathode?
5. How does a diode act as a rectifier?
6. How does the
grid control current in a triode?
7. Why must the grid be biased
8. How does a triode amplify signals?
1. How is energy transferred from the primary to the secondary of
2. Suppose d.c. were fed into the primary of
a transformer, what would happen?
3. Explain how the secondary
current controls the amount of primary current?
4. A welding
transformer has a one-turn secondary that delivers 400 amperes. The
has 800 turns. What is the primary current?
5. You want to build a transformer to step-down 440 volts to
110 volts. If 2,080 turns are
used on the secondary,
how many turns will be used on the primary?
6. A loaded secondary
draws 80 amperes at 220 volts. If the primary is 600 volts, what is
the primary current?
7. A 440/110 volt transformer is designed
for 1/4 volt per turn. How many turns on
8. Is it absolutely correct to say that transformers
ate 100 percent efficient?
9. Two losses occur in a transformer?
What are they?
10. How can the losses of a transformer be reduced?
1. How is power transferred in transformer action?
many circuits will you find in transformer action?
3. What controls
the power consumption in trans- former action?
4. Must the windings
be stationary in order to have transformer action?
ANSWERS TO QUIZZES
CHAPTER 1 MATTER
1. Protons and electrons.
1. They repel each other.
2. They attract each other.
4. Because of their weight. Electrons are
nearly 2,000 times lighter than protons.
5. Potential or potential
8. A condenser
stores an electrical charge.
ELECTRICITY IN MOTION-CURRENT
1. Each-electron acts as a-force on the others. This force moves
electrons through the wire
molecule to molecule.
2. The coulomb.
3. The ampere.
4. Potential and resistance.
5. Good conductors have
many free electrons.
6. Good insulators have few or no free
length, material and temperature.
THE ELECTRICAL CIRCUIT
1. Refer to the table in figure 15.
2. Because they reduce
3. Do not increase the circuit resistance by a
dirty or loose connection.
4. So that the fuse will melt and
open the circuit before other parts of the circuit overheat.
5. Salt water, heat, wear, and vibration.
6. Because of
the danger of a hot wire being grounded to the hull. This would produce
1. Electromotive force. The force which moves electrons.
2. Mechanical, chemical, frictional, and heat energies.
3. Generators and batteries.
4. An ion is an atom which has
lost or gained one or more electrons. It becomes a
5. A part of the primary cell is used up in
6. They can be recharged.
1. A - 4.4 amps. B - 108 v.
C - 30 ohms. D - 20 v.
2. 1 amp.
(a) Yes, the current is only 2.2 amps at 110 v. (b) No, the current
is 4.4 amps at
220 volts. This current would burn
out the lamp.
4. Voltage and resistance
1. Yes. There is an emf present. It tries to force current across
the open circuit but cannot.
2. No, as long as no current flows
it is a case of force but no motion.
3. No. Again, force but
4. 16,128 w. 16,128
kw. 2.16 hp.
5. 48,000 w.
37,300 w. 77.7 percent.
w. 30,800 w.
7. 1,350 w.
8. 0.24 ohm.
10. 93.75 hp. 69,937.5
w. 69.94 w.
THE SERIES CIRCUIT
1. A = I1 = 6a., I2 = 6a.
B:Vt = 120 v. C:Rt = 18
ohms. D:Rt = 12 ohms,
It = 0.67 a.
2. (a) 200 V., (b) 600 v.
3. (a) 2,000 w., (b) 6,000 w.
4. 0.21 a.
1. A:E1 = 12 V., E2 = 12 V., E3
= 12 v. B:It = 15a., C:Rt = 2 ohms.
D:Rt = 2 ohms.
2. 10 amps.
3. 5.45 ohms.
4. 66 amps. 3.33 ohms.
5. 5 amps.
ohms, 480 ohms, 176 ohms, 40 ohms, 24 ohms.
1. A: 150 ohms, 1.6 amps. B: E of lines = 30 volts,
E of load = 90 v.
C: 60 v, 120 v. with R out of
2. Connect the switch in series with both lamps.
3. Connect the fuse in one line between the source and the first
2. (1) Stroke unmagnetized iron against a magnet.
(2) W rap iron in a coil of wire and pass
through the coil.
3. Direction and strength.
No lines cross. (2) All lines are complete. (3) All lines leave the
magnet at right angles
to the magnet surface.
7. Always the iron.
8. Anywhere on the Agonic line.
9. The error introduced
in a compass reading due to the different locations of the
magnetic and geographic poles.
10. About 5 degrees.
11. The error introduced in a compass reading due to magnetic influences
ship or plane.
13. This iron is saturated-it is holding all the lines
1. A: correct. B: incorrect. C: incorrect. D:
2. C is the strongest.
3. Increase the coil's
1. Flux direction and the direction of cutting the flux.
2. Strength of the field, speed of the conductors, and number of
3. At least two.
5. No. The flux field must move to produce self induction.
6. For every force, there is an opposite force set up which tends
to cancel the first force.
7. Open the field coil circuit may
produce thousands of volts of self induction.
8. Pulsating d.c.
varies in strength, regular d.c. does not.
9. A.c. varies in
strength and direction, regular d.c. does not vary in either.
1. Primary-pole pieces, yoke, windings and field. Secondary-armature
consisting of coils
and iron core.
When the coil is in the neutral plane.
3. When the coil sides
are directly under the pole pieces.
4. Always a.c.
By rectifying the d.c. in a commutator.
6. More coils eliminate
the peaks and valleys of current. Pulsations are reduced.
8. Less reluctance, cheaper, easier to repair,
all coil sides cut flux.
9. The stator is the stationary part
containing the armature windings. The rotor is the
rotating part containing the field coils.
10. So that the high
voltages obtained in a.c. will not be taken off on a shipping contact.
1. Not at all. Essentially the two are alike in construction.
2. Magnetic fields.
3. The force set up by the two fields
which tends to make the generator run as a motor.
This is a Lenz's law illustration.
4. The induced voltage which
opposes the applied voltage. Another Lenz's law illustration.
5. Counter-emf controls the current by opposing the current's flow.
6. Counter-emf decreases.
7. Current will increase.
8. A starter decreases current to the armature by putting a
resistance in the armature circuit.
9. Reverse leads to either
the field or armature. Not to both!
10. Reverse armature leads
1. The series-universal motor.
A.C. coils reverse polarity with every re verse of current.
4. More than one time.
5. In electrical degrees.
8. Only the flux field produced
by the stator windings.
10. A voltage is induced
in the squirrel cage rotor. This voltage forces current through
the windings. Always a shirt circuit.
induction-exactly like the squirrel cage.
14. With d.c. from
an exciter, fed to the rotor via slip rings.
15. The field between
rotor and stator poles of a synchronous motor.
repulsion-induction, and split phase.
17. Resistance and a condenser.
1. A.C. is constantly changing in value and regularly reverses its
2. 17.675 amps.
3. Resistance keeps the current
4. Inductive reactance makes the current lag its
5. Capacitive reactance makes the current lead its
6. Add capacitive reactance by inserting a condenser.
7. (a) 6 ohms of reactance. (b) 1Q ohms of impedance. (c) The
1. Current, voltage, resistance, and power.
2. Heat, magnetism,
and motor action.
3. Hot wire, dynamometer and movable iron.
4. D'Arsonval type.
5. See diagram below.
1. The heat increases the electrons speed so that proton attraction
can no longer hold them.
2. The air molecules would clog up
the space around the cathode. They would interfere with
the emission of electrons.
3. The space charge of electrons
determine the cathode polarity. Electrons are negative so
the cathode is negative.
4. Because the plate has no electrons
emitted to make up a current from plate to cathode.
5. The diode
only passes current from cathode to plate. When the plate is negative
current can flow. Therefore, only the current
in the cathode to plate direction is passed.
6. The grid acts
as a valve between cathode and plate. The negativeness of the grid
controls the amount of current that can pass to the plate.
The grid would lose control if it became positive. Therefore, a negative
bias prevents the
grid ever becoming positive
and losing control.
8. The cathode to plate current is strong.
But this current is controlled by very small charges
in grid potential.
1. The magnetic flux field set up by the primary current carries
the primary's energy
to the secondary.
2. D.c. produces no continuous voltage of self induction, therefore
a very high current
would flow. The primary would
3. The secondary's flux field cancels the primary's.
This reduces the Esi in the primary and
adjusts primary current in exact proportions to the secondary current.
4. 1/2 ampere.
5. 8320 turns.
6. 29-1/3 amps.
7. 1,760 and 440 turns.
9. Iron losses
- hysteresis and eddy currents. Copper losses - resistance.
10. Iron, by using soft iron or silica steel in laminated form.
Copper; by shortening the
per turn, and using heavy wire. Both, by cooling entire assembly.
1. By mutual induction.
2. At least two.
4. No, all that is necessary is two circuits with pulsating
d.c. or a.c. on the primary.
- AGONIC: An imaginary line of the earth's surface passing through
points where the magnetic declination is 0°, that is, points where
the compass points true north.
- ALTERNATOR: An alternating current generator. AMMETER: The instrument
for the measurement of current.
- AMPERE: The unit of electrical current.
- AMPERE-HOUR: The quantity of electricity equivalent to a current
of one ampere flowing past a point in a conductor in one hour.
- AMPERE-TURN: The magnetizing force produced by a current of
one ampere flowing through a coil of one turn.
- ANODE: The electrode in a cell (voltaic or electrolytic) that
attracts the negative ions and repels the positive; the positive
- ARC: The luminous glow between incandescent electrodes.
- ARMATURE: The movable part of a motor or the removable part
of a magnetic circuit, such as the iron placed across the poles
of a horseshoe magnet.
- AUTO-TRANSFORMER: A transformer in which the primary and secondary
are connected together in one winding.
- BATTERY: A. group of several cells connected together as a unit.
- BRANCH CIRCUIT: One of the conductors in a parallel circuit.
- BRUSH: The conducting material, usually a block of carbon, bearing
against the commutator or slip-rings through which the current flows
in or out.
- CATHODE: The electrode in a cell (voltaic or primary) that attracts
the positive ions and repels the negative ions; the negative pole.
- CHOKE COIL: A coil of low ohmic resistance and comparatively
high impedance to alternating current.
- -CIRCUIT: The complete path of an electric current including,
usually, the generating device.
- CIRCUIT BREAKER: A device that opens a circuit while it is carrying
current; often used in abnormal conditions, such as overloads.
- CIRCULAR MIL: An area equal to that of a circle with a diameter
of 0.001 inch. It is used for measuring the cross section of wires.
- COMMUTATOR: That part of the armature of a dynamo which converts
an alternating into a direct current.
- CONDENSER: A device consisting of two or more conductors separated
by non-conductor material; it holds or stores an electric charge.
- CONDUCTANCE: The reciprocal of electrical resistance. Conducting
- CONDUCTIVITY: The ease with which a substance transmits electricity.
- CONDUCTOR: A material capable of transmitting electric current.
- CONVERTER, ROTARY: An electrical machine having a commutator
at one end and slip-rings at the other end of the armature. It is
used for the conversion of alternating to direct current.
- CORE: A mass of iron placed inside a coil to increase its magnetism.
- COULOMB: The-unit of static electricity; the quantity of electricity
transferred by one ampere in one second.
- COUNTER EMF: Counter electromotive force; an EMF induced in
a coil or armature that opposes the applied voltage.
- CURRENT OF ELECTRICITY: The continuous flow of electrons in
- D'ARSONVAL GALVANOMETER: A galvanometer in which a moving coil
swings between the poles of a permanent horseshoe magnet.
- DEMAGNETIZE: To deprive a body of its magnetic properties.
- DIELECTRIC: A non-conducting material.
- DIODE: A vacuum tube containing the filament and the plate;
it serves as a rectifier of alternating current.
- DIP NEEDLE: A magnetized needle capable of rotation in a vertical
- DIRECT CURRENT: An electric current that flows in one direction
- DYNAMO: A machine for converting mechanical energy into electrical
energy or vice versa.
- EDDY CURRENT: A current induced in the core of an armature of
a motor, dynamo, or transformer caused by changes in the magnetic
- EFFICIENCY: The ratio of a machine's useful work output to the
- ELECTRODE: The terminal by which current leaves or enters an
- ELECTROLYTE: A substance that conducts a current by the movement
- ELECTROMAGNET: A magnet made by passing current through a coil
of wire wound on a soft iron core.
- ELECTROMOTIVE FORCE (EMF): The electrical force that moves or
tends to move electrons; ELECTRON: The smallest particle of negative
- ELECTROPLATING: The electrical method of plating a surface with
- ENERGY: The ability or capacity to do work.
- FIELD: The region where a magnet or electrical charge is capable
of exerting its force.
- FIELD COIL: One of the coils used to excite a field magnet.
- FIELD MAGNET: The magnet used to produce a magnetic field (usually
in motors or generators).
- FLUX: Magnetic lines of force, assumed to flow from the north
pole to the south pole of a magnet.
- FREQUENCY: The number of cycles of an alternating current per
- FUSE: A part of a circuit made of a material that will melt
and break the circuit when current is increased beyond a specific
- GALVANOMETER: An instrument used to measure small currents.
- GENERATOR: A machine that converts mechanical energy into electrical
- GRID: A metal wire mesh placed between the cathode and plate.
- GRID BATTERY: The battery used to supply the desired potential
to the grid.
- GRID LEAK: A very high resistance placed in parallel with the
- GROUND: A connection made directly to the earth or to a frame
or structure which serves as one line of a circuit.
- HORSEPOWER: The English unit of power, equal to work done at
the rate of 550 foot-pounds per second. Equal to 746 watts of electrical
- INDUCE: To produce an effect in a body by exposing it to the
influence-of a magnetic force, an electric force, or a changing
- INDUCTION COIL: Two coils so arranged that an interrupted current
in the first produces a voltage in the second.
- INTERRUPTER: A device for the automatic making and breaking
of an electrical circuit.
- ION: An electrically charged atom.
- ISOGONIC LINE: An imaginary line drawn through points on the
earth's surface where the magnetic deviation is equal.
- JOULE: A unit of energy or work. A joule of energy is liberated
by one ampere flowing for one second through a resistance of one
- LAG: The number of degrees an alternating current lags behind
- LAMINATIONS: The thin sheets or discs making up an iron core.
- LEYDEN JAR: An early form of condenser.
- LINE OF FORCE: A line in a field of force that shows the direction
of the force.
- LOAD: The energy delivered by a generator to its circuit.
- LODESTONE: A piece of magnetite.
- MAGNETIC CIRCUIT: The complete path followed by magnetic lines
- MAGNETIC FLUX: The total number of lines of force issuing from
- MAGNETITE: An iron ore that is magnetic.
- MAGNETO: A generator in which the field is sup- plied by a permanent
- MEGOHM: A million ohms.
- MIL: One thousandth of an inch.
- MILLIAMMETER: An ammeter reading thousandths of an ampere.
- MILLIVOLTMETER: A voltmeter reading thousandths of a volt.
- MOTOR-GENERATOR (M-G): A generator driven by an electric motor.
- MUTUAL INDUCTION: The inducing of an EMF in a circuit by the
field of a nearby circuit.
- NEGATIVE CHARGE: The electrical charge carried by a body which
has an excess of electrons. (For example, a vulcanic rod, after
it has been rubbed by fur or wool, carries a negative charge.)
- NEUTRON: A particle having the weight of a pro-ton but carrying
no electric charge.
- NUCLEUS: The heavy or central part of an atom. OHMMETER: An
instrument for directly measuring ohms.
- PERMALLOY: An alloy containing 78.5 percent nickel and 21.5
percent iron. It has an abnormally high magnetic permeability.
- PERMEABILITY: A property of matter that indicates the ease with
which it is magnetized.
- PLATE CURRENT: The current that flows from the plate of a vacuum
- POLARITY: The character of having magnetic poles, or electric
- POLE: One of the ends of a magnet where most of its magnetism
- POSITIVE CHARGE: The electrical charge carried by a body which
has become deficient in electrons. (For example, a glass rod, after
it has been rubbed by silk, carries a positive charge.)
- POTENTIAL: The amount of charge held by a body.
- POWER: The time rate of doing work.
- PROTON: A positively charged, particle whose charge is equal,
but opposite, to that of the electron.
- RECTIFY: To change an alternating current to a unidirectional
or direct current.
- RELAY: An electrically operated device for the closing and opening
of a circuit.
- RELUCTANCE: A measure of the resistance of a material to magnetic
lines of force.
- RESISTANCE: The opposition of a conductor to an electric current.
- RETENTIVITY: The property of retaining magnetism.
- SATURATION, MAGNETIC: The condition of a magnetic substance
when its magnetism has reached its highest possible value.
- SELF INDUCTION: The process by which a circuit induces an EMF
in itself by its own magnetic field.
- SERIES CONNECTION: An arrangement of cells, generators, condensers,
or conductor each carries the entire current of the circuit.
- SERIES-WOUND: Having the armature wired in series with the field
winding. (Applied to motors or generators.)
- SOLENOID: A coil of wire used to produce a magnetic field.
- SPACE CHARGE: The charge acquired by the space inside a vacuum
tube due to the presence of electrons.
- STEP-DOWN TRANSFORMER: A transformer with fewer turns in the
secondary than in the primary.
- STEP-UP TRANSFORMER: A transformer with more turns in the secondary
than in the primary.
- THERMOCOUPLE: A pair of metals which generate an EMF by the
heating of one of the junctions; it is used to measure temperature
- TRANSFORMER: A device that, without moving parts, transfers
electrical energy from one circuit to another circuit by the aid
of electromagnetic induction.
- TRIODE: A vacuum tube containing a filament, grid, and plate.
- UNIDIRECTIONAL: As applied to a current of electricity, a current
that flows in one direction only.
- VACUUM TUBE: A tube from which the air has been pumped out.
The tube contains an element that emits electrons when properly
excited and an electrode to attract the electrons and set up a current
in an external circuit.
- VOLT: The practical unit of electrical pressure.
- WATT: A unit of power produced by a current of one ampere at
- WATTMETER: An instrument for measuring electric power in watts.
OHM'S LAW -
POWER EQUATION -
For IR drop
SERIES CIRCUITS -
PARALLEL CIRCUITS -
APPENDIX TABLE III
TRHLA FLB FLA GICA BW BC VLS
SCP DCP TCP FCP MCP MCS
single conductor, instrument
cable, plain. single conductor, lighting and power, ar-mored. , single
conductor, radi0, low-tension, lead- ed . single conductor, radio, high-tension,
lead- ed and armored; ,
double conductor, 'lighting and power,
armored. double conductor, lighting, braided. double conductor, radio,
high -\ tension, leaded and armored.
double conductor, radio,
low - tension, leaded.
triple conductor, lighting and power,ar¬mored
.. triple conductor, radio, high - tension, leaded and armored. four
conductor, lighting, braided. four conductor, lighting, armored._ general
interior communication (multiple conductor), armored. bell wire. bell
cord. vol tmeter leads, submarines.
RUBBER INSULATED FLEXIBLE single
conductor, portable. double conductor, portable. triple conductor, portable.
four conductor, portable. multiple conductor, portable. multiple conductor,
148. MCMB multiple conductor, marker buo,! . GICF
general interior communication conductor), flexible. TPTF twisted pair,
telephone conductors, flexi- ble.
HEAT AND FLAME RESISTANT SRI
synthetic resin insulated, single conductor. SRIB synthetk resin .insulated,
braided, single conductor. SRIG synthetic resin insulated, glass braided,
SHFW single heat and flame resistant wire,
single conductor. DHFW double heat and flame resistant wire, dou- ble
conductor. _ SHFS single heat and flame resistant, switch- board, single
conductor. SFPS single conductor, flameproof, switchboard. SHFA single-conductor,
heat and flame resistant, armored. SHFL single conductor, heat and flame
DHFA double conductor, heat and flame resist¬ant,
armored. THFA triple conductor, heat and flame resistant, armored.
FHFA four conductor, heat and flame resistant, armored.
MHFA multi-conductor, heat and flame resistant, armored.
MHFF multi-conductor, heat and flame resistant, flexible.
TTHFA twisted pair, telephone conductor, heat and flame resistant,
armored. MDGA-19-5D . multiple conductor, dega~ssing, ar-mored, 19 conductor,
50,000 eM each. 379
149. " SDGA-l,600 TSW TPTP TPTA TTHFF SLPA
single conductor, degaussing, ar.-mored, 1,600,000 eM.
SPECIAL WIRE AND' CABLE telephone switchboard wire. twisted pair, telephone,
plain. twisted pair, telephone, armored.
twisted pair, telephone,
heat and flame re-sistant, flexible .. VARNISHED CAMBRIC, INSULATED
single conductor, lighting and power, ar-mored ..
conductor, lighting and power, ar-mored. SPECIAL WIRE, OIL RESISTANT
DCOP double conductor, oil resisting, portable. TCOP / three conductor,
oil resisting, portable. FCOP four conductor, oil resisting, portable.
MCOS multi-conquctor,' oil resisting, shielded.
The suffix number
on' all power and light cables, such as SHFA,•DHFA, THFA, FHFA, SLPA,
TLPA, SCP, DCP, TCP, and FCP, always indicates the number of thousands
of circular mils in each conductor.
The suffix number on all
multiple conductor cables such as MHFA, MHFF, GICA, and GICF, indi¬cates
the number of conductors in the cable.
The suffix number on
all telephone cables, such as TTHFA, TPTA, and TPTF, indicates the number
of twisted pairs of wires in the cable. 1< u. S. GOVERNMENT PRINTING
OFFICE; 1945- 618779