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What is current flow? - โโD.The flow of electrons in a circuit What is impedance? - โโA.Opposition to alternating current Like charges will - โโB.Repel each other Any material that will readily release electrons is called: - โโB.A conductor The symbol for current is: - โโB. I Electricity can produce: - โโD. All the above light heat magnetism The safety ground conductor is usually colored: - โโB.Green An electron has: - โโB.A negative charge Which of the following materials would be best suited for use as a semi-conductor? - โโD.Silicon Which of the following meters must use internal power to check a load or circuit? - โโA.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? - โโB.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? - โโC. 2880 When testing a capacitor with an analog or digital ohmmeter, the meter should: - โโB.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? - โโA.60 ohms What is resistance? - โโA.Opposition to electron flow In electrical wiring, a black colored wire indicates: - โโA. A hot conductor How many watts are used by a heater operating on 460 volts and drawing 5 amps? - โโD. How are fuses sized? - โโD .Both A and B What is generally considered the maximum allowable supply voltage variation - โโA.5% Capacitors are rated in: - โโD .Both B and C What is the term used to describe the output side of a transformer? - โโD .Secondary side One horsepower is equal to ______ watts. - โโB. 746 A parallel circuit contains an 18 ohm and a 9 ohm resistor. What is the total resistance? - โโA.6 ohms In a series circuit, the voltage drop across each load will: - โโD .Add up to equal the source voltage
Three 300 ohm resistors are wired parallel. What is the total resistance? - โโA.100 ohms Amps can be calculated by: - โโA. E/R B.W/E C.The square root of W/R answer: D. all the above Voltage can be calculated by: - โโC.IxR An ohmmeter should never be connected to a: - โโD. Charged capacitor until it has been discharged Which of the following would be considered an inductive load? - โโD. Electric motor The voltage to ground of a high leg or "stinger leg" on a three phase open delta system will be approximately: - โโC. 208 Which of the following is the symbol for impedance? - โโD. Z What amperage measurement would you expect if you clamped your meter around both wires in a two wire circuit? - โโA.0 due to the cancellation of the two magnetic fields A diode is used to? - โโA. 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? - โโC. 3 A transformer has 1000 turns on the primary side and 500 on the secondary. What is the output if the input is 120v? - โโC. 60v
A transformer has 1000 turns on the primary side and 2000 on the secondary. What is the output if the input is 120v? - โโD. 240v If the conductor in an AC circuit is wound into a coil, the resulting EMF opposes supply voltage. This is called: - โโB. Inductive reactance To change rotation on a 3-phase motor: - โโC. Change position of any two wires A solenoid valve operates on the principle of: - โโC. Electromagnetism A ___ is commonly used on a single phase fractional horse power compressor to disconnect the start winding. - โโD. Current relay The rotation of a single phase motor is determined by: - โโA.The direction of current through the start winding Single phase motor speed is determined by: - โโB. Number of stator poles Capacitor-start, capacitor-run motors provide: - โโB. Medium running and high starting torque Direct digital control (DDC) is: - โโD. Electronic controls used for equipment control and monitoring What connects the T1, T2 and T3 terminals on a contactor? - โโB. Load wires A step-up transformer increases - โโB. voltage Utility companies usually provide residential homes with: - โโB. 240v, single phase, three wire
When the temperature of a negative temperature coefficient (NTC) thermistor increases, its resistance: - โโB. Decreases When the temperature of a positive temperature coefficient (PTC) thermistor increases, its resistance: - โโA.Increases The most common type of transducer used with HVAC/R equipment creates a signal based on: - โโD. Pressure A thermocouple can: - โโC. Generate a small DC current To discharge a capacitor: - โโB. 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? - โโD. 37.5MFD, 440VAC When checking the windings on a three phase motor, the resistance readings should: - โโC. All read the same Capacitors are always connected _____ with the start winding? - โโA. In series The symbol for a heating thermostat is represented by: - โโC. The symbol for a pressure switch that closes on a rise of pressure is represented by: - โโB. The symbol for a pressure switch that opens on a rise in pressure is represented by: - โโD. The synchronous speed of a four pole, 60 Hz single phase motor is: - โโD. 1800 RPM The symbol for a transformer is: - โโC.
The symbol for a thermal overload is: - โโD. The symbol for a pressure switch is - โโA. The symbol for a thermostatic switch is: - โโB. IN the schematic, what voltage would be found across l1 to l2? - โโA. 240 volts IN the schematic,(during operation ) what voltage would be found across the condenser fan motor? - โโA. 240 volts IN the schematic,(during operation ) what voltage would be found across the transformer primary - โโB. 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.) - โโB. 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.) - โโB. 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.) - โโA. 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? - โโC. Afaulty blower motor or blower relay
