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Table of Contents.
¶ U.S. GOVERNMENT PRINTING OFFICE; 1945 - 618779
How Well Do You Know
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?
electrons are removed from an object, the object has a _____________ charge.
4. Why are electrons and not
protons removed by friction?
5. The force which causes electrons to flow is called _____________.
6. Static electricity is _____________ electrons.
7. Current electricity is _____________ electrons.
8. What 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?
is the unit of measure of current strength?
4. What two things control the strength of current?
Why are some substances good conductors?
6. 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 circuits?
6. Why are no intentional grounds used on regular
1. What does emf mean?
2. What four kinds of energy can be converted into electrical energy?
What are the two most common sources of electrical power?
4. What is an ion?
5. Why 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 drawing.
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
lamp stand (a) 110 v. (b) 220 v.?
4. What two things control current in every
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
the load in watts? In kilowatts? In hp?
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
10. How much power will be consumed by a 75 hp motor operating at 80 percent efficiency?
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
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
3. What is the total resistance of one 10 ohm resistor, one 20 ohm resistor, and one
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 total
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 the total
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.
2. Describe two methods of producing an artificial
3. What two things does a vector show about a force?
4. What are the three important facts about a
5. Like magnetic poles _____________ each other.
6. Unlike magnetic poles
_____________ each other.
7. Flux can choose either an air or an iron path. Which does it use?
Where does a compass point true north?
9. What is variation?
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 you have?
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 they pass
through the, air. Why?
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
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 zero?
3. When is the induced voltage of a rotating coil at its maximum value?
4. Is a.c. or d.c. produced inside a rotating coil?
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
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 current?
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 "Polyphase"
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 magnetic field?
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?
Does a wound rotor have an electrical connection to a source of supply?
13. How does current get in the
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 value?
3. How does resistance affect the phase of a current?
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 circuit?
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.
4. Which meter can be used on
5. Properly connect the meters and loads shown above in their circuits.
1. In thermionic emission, why do electrons shoot off the metal surface?
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 negatively?
8. How does a triode
1. How is energy transferred from the primary to the secondary of a transformer?
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 primary
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
primary and secondary?
8. Is it absolutely correct to say that transformers ate 100 percent
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?
2. How many circuits will you find in transformer
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 difference.
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
step-by-step, from molecule to molecule.
2. The coulomb.
3. The ampere.
4. Potential and
5. Good conductors have many free electrons.
6. Good insulators have few or no free electrons.
9. Diameter, length, material and temperature.
THE ELECTRICAL CIRCUIT
1. Refer to the table in figure 15.
2. Because they reduce current flow.
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.
of the danger of a hot wire being grounded to the hull. This would produce a
1. Electromotive force. The force which moves electrons.
2. Mechanical, chemical, frictional, and heat
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 delivering
6. They can be recharged.
1. A - 4.4 amps. B - 108 v. C - 30 ohms. D - 20 v.
2. 1 amp.
3. (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.
as long as no current flows it is a case of force but no motion.
3. No. Again, force but no motion.
4. 16,128 w. 16,128 kw. 2.16 hp.
5. 48,000 w. 37,300 w. 77.7 percent.
27,602 w. 30,800 w. 89.6 percent.
7. 1,350 w.
8. 0.24 ohm.
9. 11.8 v.
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
= 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.
5. 800 v.
= 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.
6. 240 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 lamp.
2. (1) Stroke unmagnetized iron against a magnet. (2) W rap iron in a coil of wire and pass
a current through the coil.
3. Direction and strength.
4. (1) 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: correct.
2. C is the strongest.
3. Increase the coil's current.
1. Flux direction and the direction of cutting the flux.
2. Strength of the field, speed of the
conductors, and number of conductors cutting.
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
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.
2. When the coil is in the neutral plane.
3. When the coil sides are directly under the pole pieces.
4. Always a.c.
5. By rectifying the d.c. in a commutator.
6. More coils eliminate the peaks and
valleys of current. Pulsations are reduced.
7. Series connections.
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
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!
armature leads only.
1. The series-universal motor.
3. No. 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.
13. By 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.
Series-universal, repulsion-induction, and split phase.
17. Resistance and a condenser.
1. A.C. is constantly changing in value and regularly reverses its direction.
2. 17.675 amps.
3. Resistance keeps the current "in phase."
4. Inductive reactance makes the current lag its voltage.
5. Capacitive reactance makes the current lead its voltage.
6. Add capacitive reactance by
inserting a condenser.
7. (a) 6 ohms of reactance. (b) 1Q ohms of impedance. (c) The current leads.
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.
air molecules would clog up the space around the cathode. They would interfere with
the emission of
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
5. The diode only passes current from cathode to plate. When the plate is negative no
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.
7. The grid would lose control if it became positive. Therefore, a negative bias
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 burn out.
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.
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
length per turn, and
using heavy wire. Both, by cooling entire assembly.
1. By mutual induction.
2. At least two.
3. Secondary current.
4. No, all that is
necessary is two circuits with pulsating d.c. or a.c. on the primary.
APPENDIX TABLE I
- 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 pole.
- 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 power.
- 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
- COUNTER EMF: Counter electromotive force; an EMF induced in a coil or armature that opposes the applied
- CURRENT OF ELECTRICITY: The continuous flow of electrons in a circuit.
- D'ARSONVAL GALVANOMETER: A galvanometer in which a moving coil swings between the poles of a permanent
- 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 plane.
- DIRECT CURRENT: An electric current that flows in one direction only.
- 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 field.
- EFFICIENCY: The ratio of a machine's useful work output to the total input.
- ELECTRODE: The terminal by which current leaves or enters an electrolytic cell.
- ELECTROLYTE: A substance that conducts a current by the movement of ions.
- 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 electricity.
- ELECTROPLATING: The electrical method of plating a surface with a metal.
- 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 second.
- FUSE: A part of a circuit made of a material that will melt and break the circuit when current is increased
beyond a specific value.
- GALVANOMETER: An instrument used to measure small currents.
- GENERATOR: A machine that converts mechanical energy into electrical energy.
- 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 grid condenser.
- GROUND: A connection made directly to the earth or to a frame or structure which serves as one line of a
- 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 power.
- INDUCE: To produce an effect in a body by exposing it to the influence-of a magnetic force, an electric
force, or a changing current.
- INDUCTION COIL: Two coils so arranged that an interrupted current in the first produces a voltage in the
- 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
- 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 ohm.
- LAG: The number of degrees an alternating current lags behind voltage.
- 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 of force.
- MAGNETIC FLUX: The total number of lines of force issuing from a pole.
- MAGNETITE: An iron ore that is magnetic.
- MAGNETO: A generator in which the field is sup- plied by a permanent magnet.
- 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: 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 tube.
- POLARITY: The character of having magnetic poles, or electric charges.
- POLE: One of the ends of a magnet where most of its magnetism is concentrated.
- 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
- 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 differences.
- 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
- VOLT: The practical unit of electrical pressure.
- WATT: A unit of power produced by a current of one ampere at one volt.
- WATTMETER: An instrument for measuring electric power in watts.
APPENDIX TABLE II
OHM'S LAW -
POWER EQUATION -
For IR drop
SERIES CIRCUITS -
PARALLEL CIRCUITS -
APPENDIX TABLE III
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.
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,
RUBBER INSULATED FLEXIBLE single conductor, portable. double conductor, portable. triple
conductor, portable. four conductor, portable. multiple conductor, portable. multiple conductor, shielded. 378
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, single conductor.
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 resistant, leaded.
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.
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 lLPA
single conductor, degaussing, ar.-mored, 1,600,000 eM.
SPECIAL WIRE AND' CABLE telephone switchboard wire. twisted pair, telephone, plain. twisted pair, telephone,
twisted pair, telephone, heat and flame re-sistant, flexible .. VARNISHED CAMBRIC, INSULATED
single conductor, lighting and power, ar-mored ..
triple 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