Electricity HVAC Exam Questions with Answers All Correct

Electricity HVAC Exam Questions with Answers All Correct how much resistance must be placed in 120V curcuit in order to limit the current to 2Amps - Answer-60 Ohms when current flows in a 2 wire circuit such as 120v, if a clamp on amp meter is clamped around both wires what measurment would you expect. - Answer-0 amps - due to cancellation of 2 fields Current flow is? - Answer-The flow of electrons in the circuit. What is the symbol for impedence in an AC CIrcuit. - Answer-Z Impedence is? - Answer-Oppostion to Alternating current flow. If contacts become badly pitted, it is acceptable to? - Answer-Replace the contacts or control. Relays are generally used to control inductive loads up to? - Answer-10 Amps When resistors are wired in parallel: - Answer-The voltage drop across each resistor will be the same as the applied source voltage. Contactors are rated according to the maximum amperage through the? - Answer- Contacts. The Drawing illustrates where the components are located in small appliances - Answer-Pictorial When the Positive Temp coeffiecent thermistor increases, its resistance will - Answer- Increase Which meter is used to bench check a motor for shorts or open windings? - Answer- Ohmmeter Capacitor start capacitor run motor provides - Answer-Eating running and high starting torque 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. Common to ground 20.4; this indicates a - Answer-A grounded condition Which of the following is an acceptable temporary replacement for a run capacitor rated at 35 MFD at 440 VAC - Answer-37.5 MFD at 440 VAC With a motor running at full load, voltmeter leads are placed on l1 and T12 terminals of the contactor. The voltmeter indicates no measurable voltage. This is an indication of - Answer-Good clean contacts How to discharge a capacitor prior to ohm meter testing - Answer-Use a 15000 or 20000 ohm, 225 watt resistor across the terminals Utility companies usually supply residential homes with service - Answer- 240v, 3-phase, 3-wire If the conductor in a AC circuit is wound into a coil, the resulting EMF opposes the supply voltage. This opposition is called - Answer-Inductive reactance What connects to the terminal t1, t2, and t3 on a contactor or motor starter? - Answer- Load connections A solenoid valve operates on the principle of - Answer-Electromagnetism Circuit breakers and fuses are primarily used to provide - Answer-Protection from an overload of current To change direction of rotation of a 3-phase motor - Answer-You must change the position of any two supply wires Which of the following motors is most energy efficient - Answer-ECM Which of the following is equal to 2.1 KW - Answer-2100 Watts Which of the following statements about current is true - Answer-Current flow will decrease when voltage increases Capacitors are rated in - Answer-Microfarads and volts The total resistance of a parallel circuit will be - Answer-Less than the smallest resistance A parallel circuit consists of three resistors. R1 equals 30 ohms, are two is equal to 15 ohms, are 3 is equal to 10 ohms. If the current through r2 is 4 amperes, what is the source voltage - Answer-60 volts Which of the following meters must use its internal power to check a load or circuit - Answer-Ohm meter Which of the following is the correct formula for determining wattage in a electrical circuit - Answer-W=E times I In electrical wiring, a black colored wire in an alternating current circuit usually indicates - Answer-The hot conductor A 3-phase load requires a minimum of - Answer-3 supply lines The electric meter on a house measures the passing through it - Answer- Amperage Fuses are sized by - Answer-Volts and amps I'm in electrical oil safety switch, what changes the pressure signal to electrical signal - Answer-Transducer Voltage to a ground of a high leg or stinger leg on a three-phase open Delta system will be approximately - Answer-120 The symbol for current is - Answer-I Which of the following would be considered an inductive load - Answer-Electric motor Which of the following materials would be best suited for use as a semiconductor - Answer-Silicon An ohmmeter should never be connected to a - Answer-Charge capacitor and until it has been discharged Voltage can be calculated by - Answer-I x r The safety ground conductor is usually color coded which colors - Answer-Green or bare Resistance can be calculated by - Answer-E / I And electron has - Answer-A positive charge A transformer has 1000 turns of wire and a primary coil and 2000 turns in the secondary coil. If 120 volts are applied the output voltage will be - Answer-240 volts Like charges - Answer-Repel each other the transformer has 1000 turns of wire in the primary coil and 5000 turns in the secondary coil. If 120 volts are applied the output voltage will be - Answer-60 volts Any material that will readily release electrons is called - Answer-A conductor An electronically commmutated motor (ECM) is designed to? - Answer-Provide proper airflow under various conditions Resistance is - Answer-Opposition to current flow 300 ohm resistors are wired in parallel. The total resistance equals - Answer-100 ohms How many watts of power are used by a heater operating at 460 volts and drawing 5 amps - Answer-2300 amps what would be the result if a 24 volt, 20 ohm low voltage contactor coil wired in series with a 24-volt, 200 ohm control relay coil - Answer-Only a control relay would operate A capacitor analyzer is designed to - Answer-The capacitance of a capacitor 3 defrost heaters, each 15 ohms, are wired in parallel to a 120 volt power supply. How many watts of power will be used - Answer-2880 Watts Which of the following is equal to 100 milliamps - Answer-0.10 amps Which of the following is generally considered to be within the maximum allowable supply voltage variation - Answer-15% When testing a capacitor with an analog or digital ohmmeter, the meter should - Answer-Measure low Resistance then return to a high reading In a series circuit, the voltage drop across each resistance (Load) will - Answer-Add up to equal The source voltage