Electricity - Basic Navy Training Courses
NAVPERS 10622
NAVPERS 10622
Here is the "Electricity - Basic Navy Training Courses" (NAVPERS 10622) in its entirety. It should provide one of the Internet's best resources for people seeking a basic electricity course - complete with examples worked out. See copyright. See Table of Contents.
¶ U.S. GOVERNMENT PRINTING OFFICE; 1945 - 618779
QUIZZES: How Well Do You Know CHAPTER 1 MATTER 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? CHAPTER 2 STATIC ELECTRICITY 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. 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? CHAPTER 3 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 current strength? 4. What two things control the strength of current? 5. 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? CHAPTER 4 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 Navy ships? CHAPTER 5 EMF 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? 5. Why can't primary cells be recharged? 6. What is the principal advantage of secondary cells? CHAPTER 6 OHM'S LAW 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 circuit? CHAPTER 7 ELECTRICAL POWER 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? 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 drop? 10. How much power will be consumed by a 75 hp motor operating at 80 percent efficiency? In hp? In watts? In kilowatts? CHAPTER 8 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? CHAPTER 9 PARALLEL CIRCUITS 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 total resistance? 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 current required? 6. What is the resistance of each device in problem 5? What is the total resistance? CHAPTER 10 SERIES-PARALLEL CIRCUITS 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? CHAPTER 11 MAGNETISM 1. All magnets have at least _____________ poles. 2. Describe 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 _____________ each other. 6. Unlike magnetic poles _____________ each other. 7. Flux can choose either an air or an iron path. Which does it use? 8. 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? 14. Permanent magnets have a high _____________. CHAPTER 12 ELECTROMAGNETISM 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? CHAPTER 13 INDUCTION 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.? CHAPTER 14 GENERATORS 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 even voltage? 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? CHAPTER 15 D-C MOTORS 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? CHAPTER 16 A-C MOTORS 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" mean? 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? 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? CHAPTER 17 A-C CIRCUITS 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? 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 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? CHAPTER 18 ELECTRICAL METERS 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 d.c. only? 5. Properly connect the meters and loads shown above in their circuits. CHAPTER 19 VACUUM TUBES 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 amplify signals? CHAPTER 20 TRANSFORMERS 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 on primary and secondary? 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? CHAPTER 21 ELECTRICAL MACHINES 1. How is power transferred in transformer action? 2. How 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. 2. Proton. 3. Electron. 4. Atoms. CHAPTER 2 STATIC ELECTRICITY 1. They repel each other. 2. They attract each other. 3. Positive. 4. Because of their weight. Electrons are nearly 2,000 times lighter than protons. 5. Potential or potential difference. 6. Stationary. 7. Moving. 8. A condenser stores an electrical charge. CHAPTER 3 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 resistance. 5. Good conductors have many free electrons. 6. Good insulators have few or no free electrons. 7. Increased. 8. Decreased. 9. Diameter, length, material and temperature. CHAPTER 4 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. 6. Because of the danger of a hot wire being grounded to the hull. This would produce a short circuit. CHAPTER 5 EMF 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 charged particle. 5. A part of the primary cell is used up in delivering current. 6. They can be recharged. CHAPTER 6 OHM'S LAW 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 CHAPTER 7 ELECTRICAL POWER 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 no motion. 4. 16,128 w. 16,128 kw. 2.16 hp. 5. 48,000 w. 37,300 w. 77.7 percent. 6. 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. CHAPTER 8 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. 5. 800 v. CHAPTER 9 PARALLEL CIRCUITS 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. 6. 240 ohms, 480 ohms, 176 ohms, 40 ohms, 24 ohms. CHAPTER 10 SERIES-PARALLEL CIRCUITS 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 circuit. 2. Connect the switch in series with both lamps. 3. Connect the fuse in one line between the source and the first lamp. CHAPTER 11 MAGNETISM 1. Two. 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. 5. Repel. 6. Attract. 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 aboard the ship or plane. 12. 10. 13. This iron is saturated-it is holding all the lines it can. 14. Retentivity. CHAPTER 12 ELECTROMAGNETISM 1. A: correct. B: incorrect. C: incorrect. D: correct. 2. C is the strongest. 3. Increase the coil's current. CHAPTER 13 INDUCTION 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. 4. One. 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. CHAPTER 14 GENERATORS 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. CHAPTER 15 D-C MOTORS 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 only. CHAPTER 16 A-C MOTORS 1. The series-universal motor. 2. South. 3. No. A.C. coils reverse polarity with every re verse of current. 4. More than one time. 5. In electrical degrees. 6. Out-of-time. 7. No. 8. Only the flux field produced by the stator windings. 9. No. 10. A voltage is induced in the squirrel cage rotor. This voltage forces current through the windings. Always a shirt circuit. 12. No. 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. 16. Series-universal, repulsion-induction, and split phase. 17. Resistance and a condenser. CHAPTER 17 A-C CIRCUITS 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. CHAPTER 18 ELECTRICAL METERS 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.
CHAPTER 19 VACUUM TUBES 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 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 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. CHAPTER 20 TRANSFORMERS 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. 4. 1/2 ampere. 5. 8320 turns. 6. 29-1/3 amps. 7. 1,760 and 440 turns. 8. No. 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. CHAPTER 21 ELECTRICAL MACHINES 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 ELECTRICAL TERMS
APPENDIX TABLE II ELECTRICAL FORMULAS OHM'S LAW - For voltage: For current: For resistance: POWER EQUATION - For power For current For voltage COUNTER-EMF - For current For IR drop TRANSFORMERS - Voltage-turns Current-turns Power Ampere-turns SERIES CIRCUITS - For voltage For current For resistance PARALLEL CIRCUITS - For voltage For current For resistance HORSEPOWER - For hp For watts APPENDIX TABLE III CABLE DESIGNATIONS RUBBER INSULATION SICP SLPA SRLL SRHLA DLPA DLB DRHLA DRLL TLPA 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, 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. 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 lLPA 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 .. 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 |
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