Electricity: HVAC Exam Questions and Answers, Exams of Electronics engineering

Download Electricity: HVAC Exam Questions and Answers and more Exams Electronics engineering in PDF only on Docsity! HVAC Excellence - ELECTRICITY with 100+ correct questions and answers exam Current flow is: - >>>The flow of electrons in the circuit. Impedance is: - >>>Opposition to alternating current flow. Like charges; - >>>repel each other. Any material that will readily release electrons is called; - >>>A conductor The symbol for current is; - >>>I Which of the following materials would be best suited for use as a semi-conductor? - >>>silicon The safety ground conductor is usually color coded; - >>>green or bare. An electron has; - >>>a negative charge. Resistance is: - >>>Opposition to current flow. How many watts of power are used by a heater operating at 240 volts and drawing 5 amps? - >>>1200 watts Which of the following meters must use its internal power to check a load or circuit? - >>>Ohmmeter In electrical wiring, a black colored wire in an alternating current circuit usually indicates; - >>>the hot conductor. Fuses are sized by: - >>>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? - >>>Only the control relay would operate. Three defrost heaters, each 15 ohms are wired in parallel to a 120 volt power supply. How many watts of power will be used? - >>>2880 Watts Which of the following is generally considered to be within the maximum allowable (plus or minus) supply voltage variation? - >>>5% Capacitors are rated in - >>>Microfarads & Volts. When testing a capacitor with an analog or digital ohmmeter, the meter should; - >>>measure low resistance then return to high reading. What is the term used to describe the output side of a transformer? - >>>Secondary side. One horsepower is equal to __________ watts. - >>>746 How much resistance must be placed in a 120 volt circuit in order to limit the current to 2 amps? - >>>60 Ohms A parallel circuit contains a 18 ohm and a 9 ohm resistor. The total resistance equals; - >>>6 ohms. 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? - >>>Zero amps due to cancelation of the two fields. If the conductor in an AÇ circuit is wound into a coil, the resulting EMF opposes the supply voltage. This opposition is called. - >>>inductive reactance. A diode is used to; - >>>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. - >>>current relay Direction of rotation of a single phase induction motor is determined by. - >>>the direction of current flow through the start winding. Single phase motor speed is determined by the. - >>>number of stator poles. The capacitor start-capacitor run (CSCR) motor provides; - >>>high starting and running torque. To change direction of rotation of a three phase motor. - >>>change the position of any two supply wires. Capacitors are always connected _____________ to the start winding. - >>>in series Which meter is used to bench check a motor for shorts or open windings? - >>>ohmmeter. A solenoid valve coil operates on the principle of - >>>electromagnetism. When checking the windings of a three phase motor; - >>>all three terminals should show the same resistance. When testing the windings of a single phase motor, - >>>the common to run terminals show the lowest resistance. Direct Digital Control (DDC) is - >>>electronic controls use for equipment operation and monitoring A step up transformer increases; - >>>voltage. Transformers are rated according to; - >>>VA at the secondary. Utility companies usually supply residential homes with ______________ service. - >>>240V, single phase, three wire What connects to the terminals T1, T2, & T3 on a contactor or motor starter? - >>>Load connections Circuit breakers & fuses are primarily used to provide; - >>>protection from an overload of current. Excessive current can be caused by; - >>>short circuit. A device with overload protection used to control a motor is a; - >>>line starter. Relays are generally used to control inductive loads up to __________ amps. - >>>10 Contactors are rated according to the maximum amperage through the; - >>>contacts. What is the minimum number of wires required between two Start/Stop push button controls? - >>>3 If contacts become badly pitted, it is acceptable to. - >>>replace the contacts or control The thermal overload contacts on a line starter are usually_______________ reset. - >>>manual The ______________ drawing illustrates where the components are located in small appliances. - >>>pictorial Which of the following motors is most energy efficient. - >>>ЕСM On a good single-phase compressor motor, which winding terminals have the highest resistance? - >>>run to start. When testing a motor with an ohmmeter, the following measurements are recorded, Common to run 4 ohms, Common to start 6.2 ohms, Run to start 10.2 ohms, and Common to ground 20.4; This indicates a/an; - >>>grounded condition. With a motor running at full load, voltmeter leads are placed on L1 and T1 terminals of the contactor. The voltmeter indicates no measurable voltage. This is an indication of. - >>>good clean contacts. When the temperature of a negative temperature coefficient (NTC) thermistor increases, its resistance will. - >>>decrease. When the temperature of a positive temperature coefficient (PTC) thermistor increases, its resistance wilI; - >>>increase. A transducer can create a signal based on. - >>>pressure. In the schematic, the coil on line #12 controls the. - >>>blower motor relay. In the schematic, if the fuse in L2 is blown the. - >>>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? - >>>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? - >>>24 Volts How many Watts of Power are used by a heater operating at 460 Volts and drawing 5 Amps? - >>>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 - >>>both bulbs light A 240 Volt, 3 wire circuit can be split into two 120 Volt circuits. - >>>TRUE Which of the following in not a factor in determining impedance in an AC circuit? - >>>Frequency When current flows, a _______________ is produced around the conductor. - >>>magnetic field Technician #1 says that an open transformer coil is indicated by a reading of infinity on an analog ohmmeter. Technician #2 says that a shorted transformer coil is indicated by a reading of infinity on an analog ohmmeter. Which technician is correct, or are both technicians correct? - >>>Technician #2 only The terminals T1, T2, & T3 are located at the _______ of a contactor. - >>>top Circuit fuses and breakers are primarily used to protect - >>>loads