Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
A comprehensive study guide or practice exam for an electrical test, covering a wide range of topics related to electrical theory, components, and systems. Numerous multiple-choice questions with detailed explanations of the correct answers, making it a valuable resource for individuals preparing for an electrical exam or certification. The content covers fundamental concepts such as current, resistance, impedance, and power, as well as more specialized topics like transformers, motors, and control systems. By studying this document, students can gain a thorough understanding of the key principles and practical applications of electrical systems, which are essential for success in various electrical-related fields, such as engineering, maintenance, or installation. The level of detail and the comprehensive nature of the content suggest that this document could be useful for both entry-level and more experienced professionals seeking to enhance their electrical knowledge and skills.
Typology: Exams
1 / 7
What is current flow? - Correct Answer-D.The flow of electrons in a circuit What is impedance? - Correct Answer-A.Opposition to alternating current Like charges will - Correct Answer-B.Repel each other Any material that will readily release electrons is called: - Correct Answer-B.A conductor The symbol for current is: - Correct Answer-B. I Electricity can produce: - Correct Answer-D. All the above light heat magnetism The safety ground conductor is usually colored: - Correct Answer-B.Green An electron has: - Correct Answer-B.A negative charge Which of the following materials would be best suited for use as a semi-conductor? - Correct Answer-D.Silicon Which of the following meters must use internal power to check a load or circuit? - Correct Answer-A.Ohmmeter What would be the result if a 24 volt, 20 ohm contactor coil was wired in series with a 24 volt, 200 ohm control relay? - Correct Answer-B.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 are consumed? - Correct Answer-C. 2880 When testing a capacitor with an analog or digital ohmmeter, the meter should: - Correct Answer-B.Measure low resistance then return to a high reading How much resistance must be placed in a 120 volt circuit to limit the current to 2 amps?
How many watts are used by a heater operating on 460 volts and drawing 5 amps? - Correct Answer-D. How are fuses sized? - Correct Answer-D .Both A and B What is generally considered the maximum allowable supply voltage variation - Correct Answer-A.5% Capacitors are rated in: - Correct Answer-D .Both B and C What is the term used to describe the output side of a transformer? - Correct Answer- D .Secondary side One horsepower is equal to ______ watts. - Correct Answer-B. 746 A parallel circuit contains an 18 ohm and a 9 ohm resistor. What is the total resistance?
Which of the following is equal to 100 milliamps? - Correct Answer-C. 0.10 amps The meter on a house measures the ____ passing through it. - Correct Answer-C. Watts What is the correct formula for determining wattage? - Correct Answer-A.W = E x I A parallel circuit consists of three resistors; R1 = 30 ohms, R2 = 15 ohms, R3 = 10 ohms. If the current through R2 = 4 amps, what is the source voltage? - Correct Answer-B.60 volts Three 300 ohm resistors are wired parallel. What is the total resistance? - Correct Answer-A.100 ohms Amps can be calculated by: - Correct Answer-A. E/R B.W/E C.The square root of W/R answer: D. all the above Voltage can be calculated by: - Correct Answer-C.IxR An ohmmeter should never be connected to a: - Correct Answer-D. Charged capacitor until it has been discharged Which of the following would be considered an inductive load? - Correct Answer-D. Electric motor The voltage to ground of a high leg or "stinger leg" on a three phase open delta system will be approximately: - Correct Answer-C. 208 Which of the following is the symbol for impedance? - Correct Answer-D. Z What amperage measurement would you expect if you clamped your meter around both wires in a two wire circuit? - Correct Answer-A.0 due to the cancellation of the two magnetic fields A diode is used to? - Correct Answer-A. Control the direction of electron flow Three resistors are wired parallel. Two have a value of 12 ohms, one of 6. What is the total resistance? - Correct Answer-C. 3 A transformer has 1000 turns on the primary side and 500 on the secondary. What is the output if the input is 120v? - Correct Answer-C. 60v A transformer has 1000 turns on the primary side and 2000 on the secondary. What is the output if the input is 120v? - Correct Answer-D. 240v
If the conductor in an AC circuit is wound into a coil, the resulting EMF opposes supply voltage. This is called: - Correct Answer-B. Inductive reactance To change rotation on a 3-phase motor: - Correct Answer-C. Change position of any two wires A solenoid valve operates on the principle of: - Correct Answer-C. Electromagnetism A ___ is commonly used on a single phase fractional horse power compressor to disconnect the start winding. - Correct Answer-D. Current relay The rotation of a single phase motor is determined by: - Correct Answer-A.The direction of current through the start winding Single phase motor speed is determined by: - Correct Answer-B. Number of stator poles Capacitor-start, capacitor-run motors provide: - Correct Answer-B. Medium running and high starting torque Direct digital control (DDC) is: - Correct Answer-D. Electronic controls used for equipment control and monitoring What connects the T1, T2 and T3 terminals on a contactor? - Correct Answer-B. Load wires A step-up transformer increases - Correct Answer-B. voltage Utility companies usually provide residential homes with: - Correct Answer-B. 240v, single phase, three wire Transformers are rated by: - Correct Answer-B. VA at the secondary Circuit breakers and fuses are used to provide: - Correct Answer-C. Protection from an overload of current Excessive current can be caused by: - Correct Answer-D. Short circuit A device with overload protection used to control a motor is a: - Correct Answer-D. Line starter What is the minimum number of wires required between two start/stop push button controls? - Correct Answer-B. 1 If contacts become badly pitted, it is acceptable to: - Correct Answer-B. Replace the contacts or control
The thermal overload contacts on a line starter are usually ___ reset. - Correct Answer- A.Manual Which of the following motors is most energy efficient? - Correct Answer-B. ECM Contactors are rated according to the maximum amperage through the: - Correct Answer-B. Contacts The ____ drawing illustrates where the components are located on the appliance. - Correct Answer-A.Pictorial On a good single phase compressor, which winding terminals have the highest resistance? - Correct Answer-A.Run to start When testing a motor with an ohmmeter, the following measurements are recorded; C to R = 4, C to S = 6.2, R to S = 10.2, R to ground = 20.4. This indicates: - Correct Answer-B. A grounded condition With a motor running at full load, voltmeter leads are placed on L1 and T1 with no measurable voltage detected. This indicates: - Correct Answer-C. Good, clean contacts When the temperature of a negative temperature coefficient (NTC) thermistor increases, its resistance: - Correct Answer-B. Decreases When the temperature of a positive temperature coefficient (PTC) thermistor increases, its resistance: - Correct Answer-A.Increases The most common type of transducer used with HVAC/R equipment creates a signal based on: - Correct Answer-D. Pressure A thermocouple can: - Correct Answer-C. Generate a small DC current To discharge a capacitor: - Correct Answer-B. Use a 15,000 to 20,000 ohm, 2 to 5 watt resistor across the terminals Which of the following is an acceptable temporary replacement capacitor for a 35MFD, 440VAC capacitor? - Correct Answer-D. 37.5MFD, 440VAC When checking the windings on a three phase motor, the resistance readings should: - Correct Answer-C. All read the same Capacitors are always connected _____ with the start winding? - Correct Answer-A. In series The symbol for a heating thermostat is represented by: - Correct Answer-C.
The symbol for a pressure switch that closes on a rise of pressure is represented by: - Correct Answer-B. The symbol for a pressure switch that opens on a rise in pressure is represented by: - Correct Answer-D. The synchronous speed of a four pole, 60 Hz single phase motor is: - Correct Answer- D. 1800 RPM The symbol for a transformer is: - Correct Answer-C. The symbol for a thermal overload is: - Correct Answer-D. The symbol for a pressure switch is - Correct Answer-A. The symbol for a thermostatic switch is: - Correct Answer-B. IN the schematic, what voltage would be found across l1 to l2? - Correct Answer-A. 240 volts IN the schematic,(during operation ) what voltage would be found across the condenser fan motor? - Correct Answer-A. 240 volts IN the schematic,(during operation ) what voltage would be found across the transformer primary - Correct Answer-B. 240 volts In the schematic, what voltage would be found from termianl G to the load side of the transformer? (Assume the thermostat is in the closed position and the fan is set to auto.) - Correct Answer-B. 24 volts In the schematic, what voltage would be found (during operation) acros the contacts when energized in line #8? (Assume the thermostat is in the closed position and the fan is set to auto.) - Correct Answer-B. 0 volts Ine the schematic, what voltage would be be found from terminal Y to the input side of the coil on the line #11? (Assume the thermostat is in the closed position and the fan is set to auto.) - Correct Answer-A. 0 volts When troubleshooting a A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and the condenser fan motor are short cycling. The blower motor is not running. This could be caused by? - Correct Answer-C. Afaulty blower motor or blower relay
When troubleshooting a A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and the condenser fan motor are not running. The blower motor is running. This could be caused by? - Correct Answer-C. the hp,lp,overloads, oil pressure switch are open