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