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Bartleby Sitemap - Textbook Solutions

All Textbook Solutions for Delmar's Standard Textbook Of Electricity

What is the most important rule of electrical safety?2RQ What range of electric current generally causes death?What is fibrillation of the heart?5RQ Who is responsible for enforcing OSHA regulations?7RQ What is an MSDS?A padlock is used to lock out a piece of equipment. Who should have the key?A ladder is used to reach the top of a building 16 feet tall. What distance should the bottom of the ladder be placed from the side of the building?What is a ground fault?What is the approximate current at which a ground-fault detector will open the circuit?Name three devices used to provide ground-fault protection.What type of fire is Class B?What section of the NEC covers grounding?What are the three principal parts of an atom, and what charge does each carry?How many times smaller is an electron than a proton?State the law of charges.How many times more does a proton weigh than an electron?How many valence electrons are generally contained in materials used for conductors?How many valence electrons are generally contained in materials used for insulators?What is electricity?What is a gluon?It is theorized that protons and neutrons are actually formed from a combination of smaller particles. What are these particles called?What is a coulomb?What is an ampere?Define voltage.Define ohm.Define watt.An electric heating element has a resistance of 16 and is connected to a voltage of 120 V. How much current will flow in this circuit?How many watts of heat are being produced by the heating element in Question 6?A 240-V circuit has a current flow of 20 A. How much resistance is connected in the circuit?A 240-V circuit has a current flow of 20 A. How much resistance is connected in the circuit?A 240-V air-conditioning compressor has an apparent resistance of 8 . How much current will flow in the circuit?11RQ A 5-kW electric heating unit is connected to a 240-V line. What is the current flow in the circuit?Is it less expensive to operate the electric heating unit in Question 12 on 240 V or 120V?14. Is it less expensive to operate the electric heating unit in Question 12 on 240 V or 120 V? You are an electrician on the job. The electrical blueprint shows that eight 500-W lamps are to be installed on the same circuit. The circuit voltage is 277 V and is protected by a 20-A circuit breaker. A continuous-use circuit can be loaded to only 80% of its rating. Is a 20-A circuit large enough to carry this load?You have been sent to a new home. The homeowner reports that sometimes the electric furnace trips the 240-V, 60-A circuit breaker connected to it. Upon examination, you find that the furnace contains three 5000-W heating elements designed to turn on in stages. For example, when the thermostat calls for heat, the first 5000-W unit turns on. After some period of time, the second unit will turn on, and then, after another time delay, the third unit will turn on. What do you think the problem is, and what would be you recommendation for correcting it? Explain your answer.You are an electrician installing the wiring in a new home. The homeowner desires that a ceiling fan with light kits be installed in five different rooms. Each fan contains a light kit that can accommodate four 60-watt lamps. Each fan motor draws a current of 1.8 amperes when operated on high speed. It is assumed that each fan can operate more than three hours at a time and therefore must be considered a continuous-duty device. The fans are to be connected to a 15-ampere circuit. Because the devices are continuous-duty, the circuit current must be limited to 80% of the continuous connected load. How many fans can be connected to a single 15-ampere circuit? How many circuits will be required to supply power to all five fans?A homeowner is installing a swimming pool. You have been asked to install a circuit to operate a 600-watt underwater light and a circulating pump. The motor nameplate reveals that the pump has a current draw of 8.5 amperes. The devices are considered continuous-duty. Can the power to operate both of these devices be supplied by a single 20-ampere circuit?A homeowner is installing a swimming pool. You have been asked to install a circuit to operate a 600-watt underwater light and a circulating pump. The motor nameplate reveals that the pump has a current draw of 8.5 amperes. The devices are considered continuous-duty. Can the power to operate both of these devices be supplied by a single 20-ampere circuit?Why is static electricity considered to be a charge and not a current?If electrons are removed from an object, is the object positively or negatively charged?Why do static charges accumulate on insulator materials only?What is an electroscope?An electroscope has been charged with a negative charge. An object with an unknown charge is brought close to the electroscope. The leaves of the electroscope come closer together. Does the object have a positive or a negative charge?Can one thundercloud contain both positive and negative charges?A thundercloud has a negative charge, and an object on the ground has a positive charge. Will the lightning discharge be from the cloud to the ground or from the ground to the cloud?Name two devices used for lighting protection.What type of material is used to coat the aluminum drum of a copy machine?What special property does this material have that makes it useful in a copy machine?1RQ What were early natural magnets known as?The south pole of one magnet is brought close to the south pole of another magnet. Will the magnets repel or attract each other?How can the polarity of an electromagnet be determined if the direction of current flow is know?Define the following terms: Flux density Permeability Reluctance Saturation Coercive force Residual magnetism A force of 1 ounce is equal to how many dynes?Name three types of fixed resistors.What is the advantage of a metal film resistor over a carbon resistor?What is the advantage of a wire-wound resistor?How should tubular wire-wound resistors be mounted and why?A 0.5-W, 2000- resistor has a current flow of 0.01 A through it. Is this resistor operating within its power rating?A 1-W, 350- resistor is connected to 24 V. Is this resistor operating within its power rating?A resistor has color bands of orange, blue, yellow, and gold. What are the resistance and tolerance of this resistor?A 10,000- resistor has a tolerance of 5%. What are the minimum and maximum values of this resistor?Is 51,000 a standard value for a 5% resistor?What is a potentiometer?1PA You are working on an electronic circuit. The circuit current is 5 mA. A resistor is marked with the following bands: brown, black, red, gold. A voltmeter measures a voltage drop of 6.5 V across the resistor. Is this resistor within its tolerance rating?A homeowner uses a 100-watt incandescent lamp as a heater in an outside well pump house to protect the pump from freezing in cold weather. Unfortunately, however, the lamp can burn out and leave the pump unprotected. You have been asked to install a heater that will not burn out and leave the pump unprotected. You have available a 100-watt, 150-ohm wire-wound resistor. Can this resistor be connected to the 120-volt source without damage to the resistor? If so, what would be the power output of the resistor?You have determined that a 4700-ohm, 1/2-watt resistor on an electronic circuit board is defective. Assuming room permits, can the resistor be replaced with a 4700-ohm, 1 -watt resistor without damage to the rest of the board, or will the higher-wattage resistor generate excessive heat that could damage other components?Resistors Fill in the missing values. 1st Band 2nd Band 3rd Band 4th Band Value % Tolerance Red Yellow Brown Silver 6800 5 Orange Orange Orange Gold 12 2 Brown Green Silver Silver 1.8 M 10 Brown Black Yellow None 10 k 5 Violet Green Black Red 4.7 k 20 Gray Red Green Red 5.6 2 A series circuit has individual resistor values of 200,86,91,180,and150. What is the total resistance of the circuit?A series circuit contains four resistors. The total resistance of the circuit is 360 . Three of the resistors have values of 56,110,and75. What is the value of the fourth resistor?A series circuit contains five resistors. The total voltage applied to the circuit is 120 V. Four resistors have voltage drops of 35 V, 28 V, 22 V, and 15 V. What is the voltage drop of the fifth resistor?A circuit has three resistors connected in series. Resistor R2 has a resistance of 220 and voltage drop of 44 V. What is the current flow through resistor R3?A circuit has four resistors connected in series. If each resistor has a voltage drop of 60 V, what is the voltage applied to the circuit?Define a series circuit.State the three rules for series circuits.A series circuit has resistance values of 160,100,82, and 120. What is the total resistance of this circuit?If a voltage of 24 V is applied to the circuit in Question 8, what will be the total amount of current flow in the circuit?Referring to the circuit described in Questions 8 and 9, determine the drop across each of the resistors. 160,V100,V82,V120,V A series circuit contains the following values of resistors: R1=510R2=680R3=390R4=750 Assume a source voltage of 48 V. Use the general voltage divider formula to calculate the voltage drop across each of the resistors. E1=VE2=VE3=VE4=V Determine the resistance values using the color code and calculate all missing values in Figure 6-26. FIGURE 6-26 Determine resistor values using the color and find all missing electrical values.Determine the resistance values using the color code and calculate all missing values in Figure 6-27. FIGURE 6-27 Determine resistor values using the color and find all missing electrical values.1PA Three wire-wound resistors have the following values: 30 , 80 , and 100 . Each resistor has a voltage rating of 100 V. If these three resistors are connected in series, can they be connected to a 240-V circuit without damage to the resistors? Explain your answer.You are an electrician working in an industrial plant. A circuit contains eight incandescent lamps connected in series across 480 volts. One lamp has burned out, and you must determine which one is defective. You have available a voltmeter, ammeter, and ohmmeter. Which meter would you use to determine which lamp is defective in the shortest possible time? Explain how you would use this meter and why.4PA Using the three rules for series circuits and Ohms law, solve for the missing values. Er120V E1 E2 E3 E4 E5 Ir I1 I2 I3 I4 I5 R1 R1430 R2360 R3750 R41000 R5620 Pr P1 P2 P3 P4 P5 Use the general voltage divider formula to calculated the values of voltage drop for the following series-connected resistors. Assume a source voltage of 120 V. R1=1K R2=2.2K R3=1.8K R4=1.5K E1=V E2=V E3=V E4=V Find all missing values for the circuit shown in Figure 6-29. FIGURE 6-29 Determine resistor values using the color code, and determine all missing electrical values.Find all missing values for the circuit shown in Figure 6-30 FIGURE 6-30 Determine resistor values using the color code, and determine all missing electrical values.What characterizes a parallel circuit?Why are circuits in homes connected in parallel?State three rules concerning parallel circuits.A parallel circuit contains four branches. One branch has a current flow of 0.8A, another has a current flow of 1.2 A, the third has a current flow of 0.25A, and the fourth has a current flow of 1.5A. What is the total current flow in the circuit?Four resistors having a value of 100 each are connected in parallel. What is the total resistance of the circuit?A parallel circuit has three branches. An ammeter is connected in series with the output of the power supply and indicates a total current flow of 2.8 A. If Branch 1 has a current flow of 0.9A and Branch 2 has a current flow of 1.05A, what the current flow through Branch 3?Four resistors having values of 270,330,510, and 430 are connected in parallel. What is the total resistance in the circuit?A parallel circuit contains four resistors. The total resistance of the circuit is 120 . Three of the resistors have values of 820, and 470. What is the value of the fourth resistor?A circuit contains a 1200-, a 2200-, and a 3300- resistor connected in parallel. The circuit has a total current flow of 0.25A. How much current flows through each of the resistors?Find the resistance values using the color code and determine the missing values in Figure 7-26. FIGURE 7-26 Determine resistance values using the color and find all missing electrical values.Find the resistance values using the color code and determine the missing values in Figure 7-27. FIGURE 7-27 Determine resistance values using the color and find all missing electrical values.You have been hired by a homeowner to install a ceiling fan and light kit in a living room. The living room luminaire (light fixture) being used at present contains two 60-W lamps. After locating the circuit in the panel box, you find that the circuit is protected by a 15-A circuit breaker and is run with 14 AWG copper wire. After turning on all lights connected to this circuit, you have a current draw of 8.6 A and a voltage of 120 V. The ceiling fan light kit contains four 60-W lamps, and the fan has a maximum current draw of 1.6 A. Can this fan be connected to the existing living room circuit? Recall that a continuous-use circuit should not be loaded to more than 80% of its rated capacity.You are employed in a large industrial plant. A 480-V, 5000-W heater is used to melt lead in a large tank. It has been decided that the heater is not sufficient to raise the temperature of the lead to the desired level. A second 5000-W heater is to be installed on the same circuit. What will be the circuit current after installation of the second heater, and what is the minimum size circuit breaker that can be used if this is a continuous-duty circuit?You are an electrician. You have been asked by a homeowner to install a lighted mirror in a bathroom. The mirror contains eight 40-watt lamps. Upon checking the service panel you discover that the bathroom circuit is connected to a single 120-volt, 20-ampere circuit breaker. At present, the circuit supplies power to an electric wall heater rated at 1000 watts, a ceiling fan with a light kit, and a light fixture over the mirror. The fan motor has a full-load current draw of 3.2 amperes and the light kit contains three 60-watt lamps. The light fixture presently installed over the mirror contains four 60-watt lamps. The homeowner asked whether the present light fixture over the mirror can be replaced by the lighted mirror. Assuming all loads are continuous, can the present circuit supply the power needed to operate all the loads without overloading the circuit?A car lot uses incandescent lamps to supply outside lighting during the night. There are three strings of lamps connected to a single 20-ampere circuit. Each string contains eight lamps. What is the largest standard lamp that can be used without overloading the circuit? Standard size lamps are 25 watts, 40 watts, 60 watts, 75 watts, and 100 watts.Using the three rules for parallel circuits and Ohms law, solve for the missing values. ET E1 E2 E3 E4 IT0.942A I1 I2 I3 I4 RT R1680 R2820 R3470 R4330 PT P1 P2 P3 P4 Using the three rules for parallel circuits and Ohms law, solve for the missing values. ET E1 E2 E3 E4 IT0.00639A I1 I20.00139A I30.00154A I40.00115A RT R1 R2 R3 R4 PT P10.640W P2 P3 P4 Using the rules for parallel circuits and Ohmslaw, solve for the missing values. ETE1E2E3E4ITl1I2l33.2AI4RT3.582R116R210R3R420PTP1P2P3P4 Using the rules for parallel circuits and Ohmslaw, solve for the missing values. ETE1E2E3E4ITl1I2l3l4RTR182kR275kR356kR462kPT3.436WP1P2P3P4 A parallel circuit contains the following resistor values: R1=360R2=470R3=300R4=270lT=0.05A Find the following missing values: RT=l1=Al2=Al3=Al4=A A parallel Circuit contains the following resistor values: R1=270KR2=360KR3=430KR4=100KlT=0.006A Find thefollowingmissingvalues: RT=I1=Al2=Al3=Al4=A Find all missing values for the Circuit shown in Figure 7-28.Find all missing values for the circuit shown in Figure 7-29.Referto Figure 8-2. Replace the values shown with the following. Solvefor all theunknownvalues. IT=0.6AR1=470R2=360R3=510R4=430 2. Refer to Figure 8-5. Replace the values shown with the following. Solve for all the unknown values. 3. Refer to the circuit shown in Figure 8-2. Redraw the circuit and use the following values: Assume that an ammeter indicates a total circuit current of 15 mA. A voltmeter indicates the following voltage drops across each resistor: What is the most likely problem with this circuit? Refer to the circuit shown in Figure 6-22. The circuit has an applied voltage of 24 V and the resistors have values as follows: R1=1kR2=300R3=750R4=1k An ammeter and a voltmeter indicate the following values: IT=42.5mAI1=24mAE1=24VI2=18.5mAE2=5.5VI3=0AE3=18.5VI4=18.5mAE4=18.5V What is the most likely problem with this circuit? FIGURE 8-22 Determine resistor values using the color code and find all missing electrical values.Refer to Figure 8-21. Assume that the resistors have the following values: R1=150R2=120R3=47R4=220 Assume that an ohmmeter connected across the entire circuit indicates a value of 245 . Does this reading indicate that there is a problem with the circuit and, if so, what is the most likely problem? FIGURE 8-21 Series-parallel circuit.Use the color code to find the resistor values in Figure 8-22 and solve all missing values. FIGURE 8-22 Determine resistor values using the color code and find all missing electrical values.Use the color code to find the resistor values in Figure 8-23 and solve all missing values. FIGURE 8-23 Determine resistor values using the color code and find all missing electrical values.8. Use the color code to find the resistor values in Figure 8-24 and solve all missing values. Round off answers three places after the decimal. FIGURE 8-24 A circuit contains a 1000- and a 300- resistor connected in series with each other. The total circuit resistance must be reduced to a value of 1150 . Using standard resistance values of 5% resistors discussed in Unit 5, explain how to change the present resistance value to the value desired.Two resistors are connected in series. One resistor has a resistance of 1000 , and the other resistor value is not known. The circuit is connected to a 50-V power supply, and there is a current of 25 mA flowing in the circuit. If a 1500- resistor is connected in parallel with the unkonown resistor, how much current will flow in this circuit?A single-phase electric motor is connected to a 240-volt, 30-ampere circuit. The motor nameplate indicates that the full-load current draw of the motor is 21 amperes. The motor is conneted to an inertia load (a large flywheel) that requires several seconds for the motor to accelerate to full speed. Because of the long starting time, the motor causes the circuit breaker to trip before the load has reached full speed. Your job is connect a resistor in series with the motore during the starting period that will limit the startung current to 90% of the circuit-breaker rating. An ammeter indicates that the motor has a current draw of 64 amperes when power is fist applied to the motor. Determine the ohmic value and wattage rating of the resistor that should be connected in series with the motor during the starting period.The hot water for the heating system for a small factory is supplied by a single boiler. The bolier is locatd in a small building separate form the factory. The power supplied to the bioler is 240-volt single-phase without a netural conductor. At the present time, the small building housing the bioler has no inside lighting. The business owner desires that four 100-watt lamps be installed inside the building. All lamps are to be connected to a single switch. The lamps are to be connected to the present 240-volt sercvice inside the building. How would you accomplish this task? Explain your answer.Find the unknown values in the circuit if the applied voltage is 350 V and the resistors have the following values:Refer to the circuit shown in Figure 8-21 to solve the following problems. Find the unknown value in the circuit if the applied voltage is 75 V and the resistors have the following values:3. Find the unknown values in the circuit if the applied voltage is 18 V and the resistors have the following values: FIGURE 8-21 Series-parallel circuit. Refer to the circuit shown in Figure 8-25 to solve the following problems. 4. Find the unknown values in the circuit if the total current is 0.8 A and the resistors have the following values: FIGURE 8-25 A parallel-series circuit. 5. Find the unknown values in the circuit if the total current is 0.65 A and the resistors have the following values: FIGURE 8-25 A parallel-series circuit. Find the unknown values in the circuit if the total current is 1.2 A and the resistors have the following values: R1=75R2=47R3=220R4=160ETE1E2E3E4RTI1I2I3I4 FIGURE 8-25 A parallel-series circuit.Refer to the circuit shown in Figure 8-26 to solve the following problems. 7. FIGURE 8-26 A combination circuit. ET E1 E2 E3 E41.248V IT I1 I2 I3 I4 RT R1 R2 R3 R4 PT0.576W P10.0806W P20.0461W P30.00184W P4 E5 E6 E7 E8 E9 I5 I6 I7 I8 I9 R5 R6 R7 R8 R9 P50.0203W P60.00995W P70.0518W P80.0726W P90.288W FIGURE 8-26 A combination circuit.Find the missing values for the circuit shown in Figure 8-27. FIGURE 8-27 Combination circuit.Find the missing values for the circuit shown in Figure 8-28. FIGURE 8-28 Combination circuit.To what is the turning force of a dArsonval meter movement proportional?2RQ A DC voltmeter has a resistance of 20,000 per volt. What is the resistance of the meter if the range selection switch is set on the 250-V range?4. What is the purpose of an ammeter shunt? 5. Name two methods used to make a DC multirange ammeter. 6. How is an ammeter connected into a circuit? 7. How is a voltmeter connected into a circuit? 8. An ammeter shunt has a voltage drop of 50 mV when 50 A of current flow through it. What is the resistance of the shunt? 9. What type of meter contains its own separate power source? 10. What electrical quantity does the oscilloscope measure? 11. What is measured on the Y axis of an oscilloscope? 12. What is measured on the X axis of an oscilloscope? 13. A waveform shown on the display of an oscilloscope completes one cycle in 50 . What is the frequency of the waveform? 14. What is the major difference between a wattmeter and a d’Arsonval meter? 15. What two factors determine the turning force of a wattmeter? You are an electrician on the job. You have been given a multimeter that has the following AC voltage ranges: 30, 60, and 150. The meter states that it has a resistance of . You need to be able to measure a voltage of 277 volts. How much resistance should be inserted in series with the meter to make the 30-volt range indicate a full scale value of 300 volts? 1. A d'Arsonval meter movement has a full-scale current value of and a resistance of . What size resistor must be placed in series with this meter to permit it to indicate 10 V full scale? 2. The meter movement described in Question 1 is to be used to construct a multirange voltmeter. The meter is to have voltage ranges of 15 V. 60 V, 150 V, and 300 V (Figure 9-65). Find the values of . 3. A meter movement has a full-scale value of . A shunt is to be connected to the meter that permits it to have a full-scale current value of 2 A. What is the resistance of the shunt? 4. The meter movement in Question 3 is to be used as a multirange ammeter. An Ayrton shunt is to be used to provide full-scale current ranges of 5 A, 1 A, and 0.5 A (Figure 9-66). Find the values of . FIGURE 9-66 Ayrton shunt. 5. A digital voltmeter indicates a voltage of 2.5 V when 10 of current flow through a resistor. What is the resistance of the resistor? What is the maximum temperature rating of Type XHHW insulation when used in a wet location?2. Name two types of conductor insulation designed to be used underground. A 10 AWG copper conductor with Type THW insulation is to be run in free air. What is the maximum ampacity of this conductor if the ambient air temperature is 40C?4. Six 1/0 aluminum conductors are to be run in a conduit. Each conductor has Type THWN insulation, and the ambient air temperature is . What is the ampacity of each conductor? Name five conditions that must be met for running conductors in parallel.What is the largest solid (nonstranded) conductor listed in the wire tables? Can Type TW cable be used in an area that has an ambient temperature of 65C?How is the grounded conductor in a flat multiconductor cable 4 or larger identified?What three colors are ungrounded conductors not permitted to be?Twenty-five 12 AWG copper conductors are run in conduit. Each conductor has Type THHN insulation. The conduit is located in an area that has an ambient temperature of 95oF. What is the ampacity of each conductor? A single-hase load is located 2800 ft from its source. The load draws a current of 86 A and operates on 480 V. The maximum voltage drop at the load cannot be greater than 3%. What size aluminum conductors should be installed to operate this load?It is decided to use parallel 0000 conductors to supply the load in Question 11. How many 0000 conductors will be needed?A three-phase motor operates on 480 V and is located 1800 ft from the power source. The starting current is 235 A. What size copper conductors will be needed to supply this load if the voltage must not be permitted to drop below 6% of the terminal voltage during starting? You have been hired by a company to connect an outside lighting system to a panel box located 55 ft from the point of attachment. The conductors are to have Type THWN-2 insulation and the wire is copper. The termination temperature of the connections is not known. The lighting system is rated at 20 kW. The voltage is 240 V. Because the lights are expected to operate more than three hours at a time, they are considered continuous-duty. Using the NEC, determine the wire size needed to make this connection.2. You are a journeyman electrician in an industrial plant. You have been assigned the task of connecting a 25-kW electric heater to a 240-V, single-phase panel. The heater is located in an area with an ambient temperature of . The conductors are to be copper with Type TW insulation. The heater is expected to operate for more than three hours at a time. What size conductors would you use to connect this heater? You are an electrician working in an industrial plant. The company is constructing a maintenance shop located 225 feet from the main plant electrical system. You are to install a 400-ampere three-phase wire system in the new maintenance shop. The service is supplied by the existing plant service. The voltage is 480 volts and the voltage drop is to be kept at 3% or below at full load. The conductors are to be aluminum. What size conductors should be installed for the new service? Express your answer to the nearest standard wire size. (Note: Determine the wire size by calculating length, resistance, and voltage drop as opposed to using the National Electrical Code.)Using the above example, determine the wire size needed for the 400-ampere service in accordance with the National electrical Code. Assume that the conductors have type THWH insulation. (Note: As a general rule, for each 100 feet of conductor length the wire size is increased one standard size because of voltage drop.) 1. A 2 AWG copper conductor is 450 ft long. What is the resistance of this wire? Assume the ambient temperature to be . 2. An 8 AWG conductor is 500 ft long and has a resistance of 1.817 . The ambient temperature is . Of what material is the wire made? 3. Three 500-kcmil copper conductors with Type RHH insulation are to be used in an area that has an ambient temperature of . What is the maximum current-carrying capacity of these conductors? 4. Eight 10 AWG aluminum conductors with Type THWN insulation are installed in a single conduit. What is the maximum current-carrying capacity of these conductors? Assume an ambient temperature of . 5. A three-phase motor is connected to 480 V and has a starting current of 522 A. The motor is located 300 ft from the power source. The voltage drop to the motor cannot be greater than 5% during starting. What size copper conductors should be connected to the motor? 6. A 50-hp DC motor is connected to 250 volts. The motor does not contain a NEMA code. The motor is expected to operate for more than three hours at a time. The conductors are to be copper with type RHW-2 insulation. The motor is located in an area with an ambient temperature of . The two conductors are to be run in conduit. What size conductors should be used to connect this motor? (Note: 1 hp = 746 watts.) 7. A bank of electric heaters has a power rating of 25 kW. The heaters are connected to 480 volts. The heaters will operate for more than three hours at a time. The conductors supplying the heaters are to be aluminum with type THWN-2 insulation. The heaters are located in an area with an ambient temperature of . There will be six conductors in the conduit. What size conductors should be used for this installation? A 15-hp squirrel-cage induction motor is connected to 240 volts. The motor has a NEMA code B. The motor will operate for more than three hours at a time. The motor is in an area with an ambient temperature of 86F. There are to be three conductors in the raceway. The conductors are copper with THW-2 insulation. What size conductors should be used for this installation? (Note: 1 hp = 746 watts.)Determine the resistance of a 16 AWG copper conductor located in an area with an ambiet temperature of 188.6F (87C) with a length of 250 feet (76.2 m).Determine the ohms-per-mil-foot of an aluminum conductor located in an area with a temperature of 104F (40C). Use the NEC to determine the ampacity of the following conductors.1. Conduction in a liquid depends on the movement of _________________. What is a negative ion?3. What is a positive ion? Name three basic substances that can be used to produce ionization in a liquid.What is an electrolyte?6. What is used to hold a sulfate ion together? What is the negative terminal of a power source called?8RQ What determines the thickness of the coating during an electroplating process?What is electrolysis?11. What is ionization potential? 12. What is the most important factor in the ionization of a gas? 13. Name two factors that determine the speed an electron attains inside a gas environment. What determines the density of the molecules in a gas environment?What determines the color of light emitted by a gas-filled tube?1. What is a voltaic cell? What factors determine the amount of voltage produced by a cell?What determines the amount of current a cell can provide?4. What is a battery? 5. What is a primary cell? What is a secondary cell?7. What material is used as the positive electrode in a zinc-mercury cell? What is another name for the Leclanch cell?9. What is used as the electrolyte in a carbon-zinc cell? What is the advantage of the alkaline cell as compared with the carbon-zinc cell?What material is used as the positive electrode in an alkaline cell?12. How is the A-hr capacity of a lead-acid battery determined? What device is used to test the specific gravity of a cell?14. A 6-V lead-acid battery has an A-hr rating of 180 A-hr. The battery is to be load-tested. What should be the test current, and what are the maximum permissible amount and duration of the voltage drop? Three 12-V, 100-A-hr batteries are connected in series. What are the output voltage and A-hr capacity of this connection?What is the voltage produced by a silicon solar cell?What determines the current capacity of a solar cell?A solar cell can produce a voltage of 0.5 V and has a current capacity of 0.1 A. How many cells should be connected in series and parallel to produce an output of 6 V at 0.3 A?19RQ 20RQ 21RQ 22RQ Your job is to order and connect lead-acid cells used to supply an uninterruptible power supply (UPS). The battery output voltage must be 126 V and have a current capacity of not less than 250 A-hr. Each cell has a rating of 2 V and 100 A-hr. How many cells must be ordered and how would you connect them?A bank of nickel-cadmium cells is used as the emergency lighting supply for a hospital. There are 100 cells connected in series and each has an A-hr rating of 120 A-hr. The bank has to be replaced, and the manufacturer is no longer supplying nickel-cadmium cells. It is decided to replace the cells with lead-acid cells. How many lead-acid cells will be required if each has an A-hr rating of 60 A-hr, and how should they be connected?An office building uses a bank of 63 lead-acid cells connected in series with a capacity of 80 amp-hours each to provide battery backup for their computers. The lead-acid cells are to be replaced with nickel-metal hydride cells with a capacity of 40 amp-hours each. How many nickel-metal hydride cells will be required to replace the lead-acid cells and how should they be connected?What determines the polarity of magnetism when current flows through a conductor?What determines the strength of the magnetic field when current flows through a conductor?3. Name three factors that determine the amount of induced voltage in a coil. 4. How many lines of magnetic flux must be cut in 1 s to induce a voltage of 1 V? 5RQ Into how many time constants is an exponential curve divided?7. Each time constant of an exponential curve is equal to what percentage of the maximum amount of charge? 8. An inductor has an inductance of 0.025 H and a wire resistance of 3 . How long will it take the current to reach its full Ohm’s law value? 9RQ 10RQ 1PA 1. Which trigonometric function is used to find the angle if the length of the hypotenuse and of the adjacent side are known? 2. If side A has a length of 18.5 ft and side B has a length of 28 ft, what is the length of the hypotenuse? 3RQ 4RQ 5. The hypotenuse has a length of 65 in., and side A has a length of 31 in. What is angle X? 6RQ 7RQ 8RQ Using the dimensions in Question 8, what is the length of side B?10RQ A parking lot is 275 ft by 200 ft (Figure 14-23). A trade size 4 conduit has been buried 2 ft beneath the concrete. The conduit runs at an angle from one corner of the parking lot to the other. Two pull boxes have been placed in the conduit run. The pull boxes are equally spaced along the length of conduit. Your job is to pull conductors through the conduit from one end of the run to the other. FIGURE 14-23 Determining length. Allowing 12 ft of extra conductor, what is the length of each conductor? The conductors are not to be spliced. How much cable will be required to pull these conductors through the conduit, allowing an extra 5 ft at one end that is to be connected to the pulling device and 3 ft extra that is to be used to connect the conductors to the cable?You desire to add a solar heating system to your swimming pool to extend the length of time you can use the pool. For maximum efficiency, the collector should be placed on an angle that will permit the suns rays to strike the collector at a 90 angle (Figure 14-24). When the sun is at its highest point of the day, you place a yardstick perpendicular to a flat concrete surface. The stick casts a shadow 3.5 ft long. At what angle with respect to the ground should the solar collector be placed? FIGURE 14-24 The suns rays should strike the face of the solar collector at a 90 angle.Basic Trigonometry Refer to Figure 14-22 to find the missing values in the following chart. FIGURE 14-22 Finding the values of a right triangle.1. What is the most common type of AC waveform? 2. How many degrees are there in one complete sine wave? At what angle does the voltage reach its maximum negative value on a sine wave?4. What is frequency? 5. A sine wave has a maximum value of 230 V. What is the voltage after of rotation? A sine wave has a voltage of 63 V after 22 of rotation. What is the maximum voltage reached by this waveform?7. A sine wave has a maximum value of 560 V. At what angle of rotation will the voltage reach a value of 123 V? A sine wave has a peak value of 433 V. What is the RMS value?A sine wave has a peak-to-peak value of 88 V. What is the average value?A DC voltage has an average value of 68 V. What is the RMS value?An AC waveform has a frequency of 50 Hz. How much time is required to complete one cycle?12. An AC waveform completes one cycle in 0.8 ms. What is the frequency of the waveform? You are an electrician working on an overhead crane. The crane uses a large electromagnet to pick up large metal pipes. The magnet must have a minimum of 200 VDC to operate properly. The crane has an AC source of 240 V. You are given four diodes that have a peak voltage rating of 400 V each. These diodes are to be used to form a bridge rectifier to convert the AC voltage into DC voltage. Is the voltage rating of the diodes sufficient? To the nearest volt, what will be the DC output voltage of the bridge rectifier?You are a journeyman electrician working in a large office building. The fluorescent lighting system is operated at 277 V. You have been instructed to replace the existing light ballasts with a new electronic type that is more efficient. The manufacturer of the ballast states that the maximum peak operating voltage for the ballast is 350 V. Will the new electronic ballast operate on the buildings lighting system without harm?1. How many degrees are the current and voltage out of phase with each other in a pure resistive circuit? 2. How many degrees are the current and voltage out of phase with each other in a pure inductive circuit? To what is inductive reactance proportional?Four inductors, each having an inductance of 0.6 H, are connected in series. What is the total inductance of the circuit?Three inductors are connected in parallel. Inductor 1 has an inductance of 0.06 H; Inductor 2 has an inductance of 0.05 H; and Inductor 3 has an inductance of 0.1 H. What is the total inductance of this circuit?6. If the three inductors in Question 5 were connected in series, what would be the inductive reactance of the circuit? Assume the inductors are connected to a 60-Hz line. 7. An inductor is connected to a 240-V, 1000-Hz line. The circuit current is 0.6 A. What is the inductance of the inductor? 8. An inductor with an inductance of 3.6 H is connected to a 480-V, 60-Hz line. How much current will flow in this circuit? If the frequency in Question 8 is reduced to 50 Hz, how much current will flow in the circuit?10. An inductor has an inductive reactance of 250 V when connected to a 60-Hz line. What will be the inductive reactance if the inductor is connected to a 400-Hz line? An inductor has an inductive reactance of 80 ohms and a wire resistance of 14 ohms. What is the Q of the inductor?12. An inductor has a wire resistance of 6 ohms. The Q of the inductor is 9. Using the formula determine the inductive reactance of the inductor. An inductor has an inductive reactance of 150 ohms and a Q of 12. Using the formula R=XLQ determine the amount of wire resistance of the inductor.You are working as an electrician installing fluorescent lights. You notice that the lights were made in Europe and that the ballasts are rated for operation on a 50-Hz system. Will these ballasts be harmed by overcurrent if they are connected to 60 Hz? If there is a problem with these lights, what will be the most likely cause of the trouble?You have the task of ordering a replacement inductor for one that has become defective. The information on the nameplate has been painted over and cannot be read. The machine that contains the inductor operates on 480 V at a frequency of 60 Hz. Another machine has an identical inductor in it, but its nameplate has been painted over also. A clamp-on ammeter indicates a current of 18 A, and a voltmeter indicates a voltage drop across the inductor of 324 V in the machine that is still in operation. After turning off the power and locking out the panel, you disconnect the inductor in the operating machine and measure a wire resistance of 1.2 with an ohmmeter. Using the identical inductor in the operating machine as an example, what inductance value should you order and what would be the minimum VAR rating of the inductor? Should you be concerned with the amount of wire resistance in the inductor when ordering? Explain your answers.Inductive Circuits Fill in all the missing values. Refer to the following formulas: XL=2fLL=XL2ff=XL2L Inductance (H) Frequency (Hz) Inductive Reactance ( ) 1.2 60 0.085 213.628 1000 4712.389 0.65 600 3.6 678.584 25 411.459 0.5 60 0.85 6408.849 20 201.062 0.45 400 4.8 2412.743 1000 40.841 What frequency must be applied to a 33-mH inductor to produce an inductive reactance of 99.526 ?An inductor is connected to a 120-volt, 60-Hz line and has a current flow of 4 amperes. An ohmmeter indicates that the inductor has a wire resistance of 12 . What is the inductance of the inductor?A 0.75-henry inductor has a wire resistance of 90 . When connected to a 60-Hz power line, what is the total current-limiting effect of the inductor?An inductor has a current flow of 3 amperes when connected to a 240-volt, 60-Hz power line. The inductor has a wire resistance of 15 . What is the Q of the inductor?1. What is the relationship of voltage and current (concerning phase angle) in a pure resistive circuit? What is the relationship of voltage and current (concerning phase angle) in a pure inductive circuit?3. What is power factor? 4. A circuit contains a 20- resistor and an inductor with an inductance of 0.093 H. If the circuit has a frequency of 60 Hz, what is the total impedance of the circuit? 5. An R-L series circuit has a power factor of 86%. By how many degrees are the voltage and current out of phase with each other? 6. An R-L series circuit has an apparent power of 230 VA and a true power of 180 W. What is the reactive power? 7. The resistor in an R-L series circuit has a voltage drop of 53 V, and the inductor has a voltage drop of 28 V. What is the applied voltage of the circuit? 8. An R-L series circuit has a reactive power of 1234 VARs and an apparent power of 4329 VA. By how many degrees are voltage and current out of phase with each other? 9. An R-L series circuit contains a resistor and an inductor. The resistor has a value of 6.5 . The circuit is connected to 120 V and has a current flow of 12 A. What is the inductive reactance of this circuit? 10. What is the voltage drop across the resistor in the circuit in Question 9? 11. A phase angle meter connected in an R-L series circuit indicates that the current is 28 degrees out of phase with the voltage. What is the circuit power factor? 12. An R-L series circuit has a power factor of 73%. If the apparent power is 560 kVA, what is the true power in the circuit? An AC electric motor is connected to a 240-V, 60-Hz source. A clamp-on ammeter with a peak hold function reveals that the motor has an inrush current of 34 A when the motor is first started. Your job is to reduce the inrush current to a value of 20 A by connecting a resistor in series with the motor. The resistor will be shunted out of the circuit after the motor is started. Using an ohmmeter, you find that the motor has a wire resistance of 3 . How much resistance should be connected in series with the motor to reduce the starting current to 20 A?You are a journeyman electrician working in an industrial plant. Your task is to connect an inductor to a 480-V, 60-Hz line. To determine the proper conductor and fuse size for this installation, you need to know the amount of current the inductor will draw from the line. The nameplate on the inductor indicates that it has an inductance of 0.1 H. An ohmmeter reveals that it has a wire resistance of 10 . How much current should this inductor draw when connected to the line?

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