Download HVAC Excellence - ELECTRICITY Exam Questions and Answers and more Exams Electrical and Electronics Engineering in PDF only on Docsity!
Questions And Answers
Current flow is: - correct answer The flow of electrons in the circuit. Impedance is: - correct answer Opposition to alternating current flow. Like charges; - correct answer repel each other. Any material that will readily release electrons is called; - correct answer A conductor The symbol for current is; - correct answer I Which of the following materials would be best suited for use as a semi-conductor? - correct answer silicon The safety ground conductor is usually color coded; - correct answer green or bare. An electron has; - correct answer a negative charge.
Questions And Answers
Resistance is: - correct answer Opposition to current flow. How many watts of power are used by a heater operating at 240 volts and drawing 5 amps? - correct answer 1200 watts Which of the following meters must use its internal power to check a load or circuit? - correct answer Ohmmeter In electrical wiring, a black colored wire in an alternating current circuit usually indicates; - correct answer the hot conductor. Fuses are sized by: - correct answer Volts & Amps What would be the result, if a 24 volt, 20-ohm low voltage conta ctor coil were wired in series with a 24 volt, 200- ohm control relay coil? - correct answer Only the control relay would operate.
Questions And Answers
How much resistance must be placed in a 120 volt circuit in order to limit the current to 2 amps? - correct answer 60 Ohms A parallel circuit contains a 18 ohm and a 9 ohm resistor. The total resistance equals; - correct answer 6 ohms. In a series circuit, the voltage drop across each resistance (load) will. - correct answer add up to equal the source voltage. The total resistance of a parallel circuit will be; - correct answer less than the smallest resistance. Which of the following statements about current is true? - correct answer Current flow will increase when voltage increases. When resistors are wired in parallel; - correct answer the voltage drop across each resistor will be the same as the applied source Which of the following is equal to 2.1KW? - correct answer 2,100 Watts
Questions And Answers
Which of the following is equal to 100 milliamps? - correct answer 0.10 amperes A capacitor analyzer is designed to read; - correct answer the capacitive resistance of a capacitor. On an electronic oil safety switch what changes the pressure singal to electrical signal? - correct answer Transducer. The electric meter on a house measures the ______________ passing th rough it. - correct answer wattage A three phase load requires a minimum of; - correct answer three supply lines. Which of the following is the correct formula for determining wattage in an electrical circuit? - correct answer W = E times I A parallel circuit consists of three resistors.R1 = 30 Ohms, R2 = 15 Ohms, R3 = 10 Ohms. If the current through R
Questions And Answers
The voltage to ground of a "high Leg" or "Stinger Leg" on a three phase open Delta system will be approximately; - correct answer 208 A transformer has 1000 turns of wire in the primary coil and 500 turns in the secondary coil. If 120 volts are applied, the output voltage will be. - correct answer 60 volts A transformer has 1000 turns of wire in the primary coil and 2000 turns in the secondary coil. If 120 volts are applied, the output voltage will be; - correct answer 240 volts Which of the following is the symbol for Impedance in an AC circuit? - correct answer Z When current flows in a two wire circuit (such as 120 volts) if a clamp on amp meter is clamped around both wires. What measurement would you expect? - correct answer Zero amps due to cancelation of the two fields.
Questions And Answers
If the conductor in an AÇ circuit is wound into a coil, the resulting EMF opposes the supply voltage. This opposition is called. - correct answer inductive reactance. A diode is used to; - correct answer control the direction of electron flow. A ___________ is commonly used on a single phase capacitor start fractional horse power compressor motor to disconnect the start winding after the motor starts. - correct answer current relay Direction of rotation of a single phase induction motor is determined by. - correct answer the direction of current flow through the start winding. Single phase motor speed is determined by the. - correct answer number of stator poles. The capacitor start-capacitor run (CSCR) motor provides; - correct answer high starting and running torque.
Questions And Answers
Direct Digital Control (DDC) is - correct answer electronic controls use for equipment operation and monitoring A step up transformer increases; - correct answer voltage. Transformers are rated according to; - correct answer VA at the secondary. Utility companies usually supply residential homes with ______________ service. - correct answer 240V, single phase, three wire What connects to the terminals T1, T2, & T3 on a contactor or motor starter? - correct answer Load connections Circuit breakers & fuses are primarily used to provide; - correct answer protection from an overload of current. Excessive current can be caused by; - correct answer short circuit.
Questions And Answers
A device with overload protection used to control a motor is a; - correct answer line starter. Relays are generally used to control inductive loads up to __________ amps. - correct answer 10 Contactors are rated according to the maximum amperage through the; - correct answer contacts. What is the minimum number of wires required between two Start/Stop push button controls? - correct answer 3 If contacts become badly pitted, it is acceptable to. - correct answer replace the contacts or control The thermal overload contacts on a line starter are usually_______________ reset. - correct answer manual
Questions And Answers
When the temperature of a positive temperature coefficient (PTC) thermistor increases, its resistance wilI; - correct answer increase. A transducer can create a signal based on. - correct answer pressure. A typical thermocouple used on a gas furnace can. - correct answer generate a small DC electrical current. To discharge a capacitor prior to ohmmeter testing. - correct answer use a 20,000 ohm, 2 to 5 watt resistor across the terminals. Which of the following is an acceptable temporary replacement for a run capacitor rated at 35MFD @ 440VAC - correct answer 37.5MFD @ 440VAC. The synchronous speed of a four pole, 60 Hz single phase motor is; - correct answer 1800 rpm.
Questions And Answers
The symbol for a heating thermostat is represented by diagram. - correct answer B The symbol for a pressure switch that closes on pressure rise represented by diagram - correct answer A The symbol for a pressure switch that opens on pressure rise is represented by diagram. - correct answer C In the schematic, what voltage would be found across L to L2? - correct answer 240 volts. In the schematic, what voltage would be found across the condenser fan motor? - correct answer O volts, In the schematic, what voltage would be found across the transformer primary? - correct answer 240 volts.
Questions And Answers
When troubleshooting the A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and condenser fan are not running. The blower motor is running. This could be caused by. - correct answer the HP, LP, overloads, or oil pressure switch are open (line #11). When troubleshooting the A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and condenser fan motors are short cycling. The blower motor is not running. When the fan switch at the thermostat is moved from the AUTO position to the FAN ON position, the blower runs. This could be caused by. - correct answer a faulty thermostat - AUTO / FAN ON switch. In the schematic, the crankcase heater will operate; - correct answer when the compressor is off. in the schematic, the coil on line #11 does NOT control. - correct answer the blower motor. In the schematic, the coil on line #12 controls the. - correct answer blower motor relay.
Questions And Answers
In the schematic, if the fuse in L2 is blown the. - correct answer blower motor will continue to operate. In the schematic, with the thermostat bulb closed, what voltage would be found from Terminal Y to the Common side of the Contactor Coil on Line #11? - correct answer 24 Volts In the schematic, with the thermostat bulb closed and the fan switch in the AUTO position, what voltage would be found from Terminal R to Terminal G on the Thermostat? - correct answer 24 Volts How many Watts of Power are used by a heater operating at 460 Volts and drawing 5 Amps? - correct answer 2,300 Watts Two 120 volt incandescent light bulbs are wired in series, one is a 60 watt bulb, the other is a 4 watt bulb. The result would be - correct answer both bulbs light A 240 Volt, 3 wire circuit can be split into two 120 Volt circuits. - correct answer TRUE
