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Untitled Quiz
100 Questions
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Untitled Quiz

Created by
@BrainiestDouglasFir

Questions and Answers

What is current flow?

The flow of electrons in a circuit

What is impedance?

Opposition to alternating current

Like charges will

Repel each other

Any material that will readily release electrons is called:

<p>A conductor</p> Signup and view all the answers

The symbol for current is:

<p>I</p> Signup and view all the answers

Electricity can produce:

<p>All the above (light, heat, magnetism)</p> Signup and view all the answers

The safety ground conductor is usually colored:

<p>Green</p> Signup and view all the answers

An electron has:

<p>A negative charge</p> Signup and view all the answers

Which of the following materials would be best suited for use as a semi-conductor?

<p>Silicon</p> Signup and view all the answers

Which of the following meters must use internal power to check a load or circuit?

<p>Ohmmeter</p> Signup and view all the answers

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?

<p>Only the control relay would operate</p> Signup and view all the answers

Three defrost heaters, each 15 ohms, are wired in parallel to a 120 volt power supply. How many Watts are consumed?

<p>2880</p> Signup and view all the answers

When testing a capacitor with an analog or digital ohmmeter, the meter should:

<p>Measure low resistance then return to a high reading</p> Signup and view all the answers

How much resistance must be placed in a 120 volt circuit to limit the current to 2 amps?

<p>60 ohms</p> Signup and view all the answers

What is resistance?

<p>Opposition to electron flow</p> Signup and view all the answers

In electrical wiring, a black colored wire indicates:

<p>A hot conductor</p> Signup and view all the answers

How many watts are used by a heater operating on 460 volts and drawing 5 amps?

<p>2300</p> Signup and view all the answers

How are fuses sized?

<p>Both A and B</p> Signup and view all the answers

What is generally considered the maximum allowable supply voltage variation?

<p>5%</p> Signup and view all the answers

Capacitors are rated in:

<p>Both B and C</p> Signup and view all the answers

What is the term used to describe the output side of a transformer?

<p>Secondary side</p> Signup and view all the answers

One horsepower is equal to _____ watts.

<p>746</p> Signup and view all the answers

A parallel circuit contains an 18 ohm and a 9 ohm resistor. What is the total resistance?

<p>6 ohms</p> Signup and view all the answers

In a series circuit, the voltage drop across each load will:

<p>Add up to equal the source voltage</p> Signup and view all the answers

Which of the following is equal to 2.1kW?

<p>2100 watts</p> Signup and view all the answers

A capacitor analyzer is designed to check:

<p>The capacitance of a capacitor</p> Signup and view all the answers

On an electronic oil safety switch, what changes the pressure signal to an electrical signal?

<p>Transducer</p> Signup and view all the answers

A three-phase load requires a minimum of

<p>Three supply lines</p> Signup and view all the answers

An electronically commutated motor (ECM) is designed to:

<p>Provide proper airflow under various conditions</p> Signup and view all the answers

Resistance can be calculated by:

<p>E divided by I</p> Signup and view all the answers

The total resistance in a parallel circuit will be:

<p>Less than the smallest resistance</p> Signup and view all the answers

Which of the following statements about current is true?

<p>Current flow will increase when voltage increases</p> Signup and view all the answers

When resistors are wired in parallel:

<p>The voltage drop across each resistor will be the same as the applied source voltage</p> Signup and view all the answers

Which of the following is equal to 100 milliamps?

<p>0.10 amps</p> Signup and view all the answers

The meter on a house measures the ____ passing through it.

<p>Watts</p> Signup and view all the answers

What is the correct formula for determining wattage?

<p>W = E x I</p> Signup and view all the answers

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?

<p>60 volts</p> Signup and view all the answers

Three 300 ohm resistors are wired in parallel. What is the total resistance?

<p>100 ohms</p> Signup and view all the answers

Amps can be calculated by:

<p>All the above</p> Signup and view all the answers

Voltage can be calculated by:

<p>IxR</p> Signup and view all the answers

An ohmmeter should never be connected to a:

<p>Charged capacitor until it has been discharged</p> Signup and view all the answers

Which of the following would be considered an inductive load?

<p>Electric motor</p> Signup and view all the answers

The voltage to ground of a high leg or 'stinger leg' on a three-phase open delta system will be approximately:

<p>208</p> Signup and view all the answers

Which of the following is the symbol for impedance?

<p>Z</p> Signup and view all the answers

What amperage measurement would you expect if you clamped your meter around both wires in a two-wire circuit?

<p>0 due to the cancellation of the two magnetic fields</p> Signup and view all the answers

A diode is used to?

<p>Control the direction of electron flow</p> Signup and view all the answers

Three resistors are wired in parallel. Two have a value of 12 ohms, one of 6. What is the total resistance?

<p>3</p> Signup and view all the answers

A transformer has 1000 turns on the primary side and 500 on the secondary. What is the output if the input is 120v?

<p>60v</p> Signup and view all the answers

A transformer has 1000 turns on the primary side and 2000 on the secondary. What is the output if the input is 120v?

<p>240v</p> Signup and view all the answers

If the conductor in an AC circuit is wound into a coil, the resulting EMF opposes supply voltage. This is called:

<p>Inductive reactance</p> Signup and view all the answers

To change rotation on a 3-phase motor:

<p>Change position of any two wires</p> Signup and view all the answers

A solenoid valve operates on the principle of:

<p>Electromagnetism</p> Signup and view all the answers

A ___ is commonly used on a single phase fractional horsepower compressor to disconnect the start winding.

<p>Current relay</p> Signup and view all the answers

The rotation of a single phase motor is determined by:

<p>The direction of current through the start winding</p> Signup and view all the answers

Single phase motor speed is determined by:

<p>Number of stator poles</p> Signup and view all the answers

Capacitor-start, capacitor-run motors provide:

<p>Medium running and high starting torque</p> Signup and view all the answers

Direct digital control (DDC) is:

<p>Electronic controls used for equipment control and monitoring</p> Signup and view all the answers

What connects the T1, T2 and T3 terminals on a contactor?

<p>Load wires</p> Signup and view all the answers

A step-up transformer increases

<p>Voltage</p> Signup and view all the answers

Utility companies usually provide residential homes with:

<p>240v, single phase, three wire</p> Signup and view all the answers

Transformers are rated by:

<p>VA at the secondary</p> Signup and view all the answers

Circuit breakers and fuses are used to provide:

<p>Protection from an overload of current</p> Signup and view all the answers

Excessive current can be caused by:

<p>Short circuit</p> Signup and view all the answers

A device with overload protection used to control a motor is a:

<p>Line starter</p> Signup and view all the answers

What is the minimum number of wires required between two start/stop push button controls?

<p>1</p> Signup and view all the answers

If contacts become badly pitted, it is acceptable to:

<p>Replace the contacts or control</p> Signup and view all the answers

The thermal overload contacts on a line starter are usually ___ reset.

<p>Manual</p> Signup and view all the answers

Which of the following motors is most energy efficient?

<p>ECM</p> Signup and view all the answers

Contactors are rated according to the maximum amperage through the:

<p>Contacts</p> Signup and view all the answers

The ____ drawing illustrates where the components are located on the appliance.

<p>Pictorial</p> Signup and view all the answers

On a good single phase compressor, which winding terminals have the highest resistance?

<p>Run to start</p> Signup and view all the answers

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:

<p>A grounded condition</p> Signup and view all the answers

With a motor running at full load, voltmeter leads are placed on L1 and T1 with no measurable voltage detected. This indicates:

<p>Good, clean contacts</p> Signup and view all the answers

When the temperature of a negative temperature coefficient (NTC) thermistor increases, its resistance:

<p>Decreases</p> Signup and view all the answers

When the temperature of a positive temperature coefficient (PTC) thermistor increases, its resistance:

<p>Increases</p> Signup and view all the answers

The most common type of transducer used with HVAC/R equipment creates a signal based on:

<p>Pressure</p> Signup and view all the answers

A thermocouple can:

<p>Generate a small DC current</p> Signup and view all the answers

To discharge a capacitor:

<p>Use a 15,000 to 20,000 ohm, 2 to 5 watt resistor across the terminals</p> Signup and view all the answers

Which of the following is an acceptable temporary replacement capacitor for a 35MFD, 440VAC capacitor?

<p>37.5MFD, 440VAC</p> Signup and view all the answers

When checking the windings on a three phase motor, the resistance readings should:

<p>All read the same</p> Signup and view all the answers

Capacitors are always connected _____ with the start winding?

<p>In series</p> Signup and view all the answers

The symbol for a heating thermostat is represented by:

<hr /> Signup and view all the answers

The symbol for a pressure switch that closes on a rise of pressure is represented by:

<hr /> Signup and view all the answers

The symbol for a pressure switch that opens on a rise in pressure is represented by:

<hr /> Signup and view all the answers

The synchronous speed of a four pole, 60 Hz single-phase motor is:

<p>1800 RPM</p> Signup and view all the answers

The symbol for a transformer is:

<hr /> Signup and view all the answers

The symbol for a thermal overload is:

<hr /> Signup and view all the answers

The symbol for a pressure switch is

<hr /> Signup and view all the answers

The symbol for a thermostatic switch is:

<hr /> Signup and view all the answers

In the schematic, what voltage would be found across L1 to L2?

<p>240 volts</p> Signup and view all the answers

In the schematic (during operation) what voltage would be found across the condenser fan motor?

<p>240 volts</p> Signup and view all the answers

In the schematic (during operation) what voltage would be found across the transformer primary?

<p>240 volts</p> Signup and view all the answers

In the schematic, what voltage would be found from terminal G to the load side of the transformer? (Assume the thermostat is in the closed position and the fan is set to auto.)

<p>24 volts</p> Signup and view all the answers

In the schematic, what voltage would be found (during operation) across the contacts when energized in line #8? (Assume the thermostat is in the closed position and the fan is set to auto.)

<p>0 volts</p> Signup and view all the answers

In the schematic, what voltage would be found from terminal Y to the input side of the coil on line #11? (Assume the thermostat is in the closed position and the fan is set to auto.)

<p>0 volts</p> Signup and view all the answers

When troubleshooting an 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?

<p>A faulty blower motor or blower relay</p> Signup and view all the answers

When troubleshooting an 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?

<p>The HP, LP, overloads, oil pressure switch are open</p> Signup and view all the answers

In the schematic, a faulty thermostat - auto / fan on switch means?

<p>The device is not functioning correctly</p> Signup and view all the answers

In the schematic, the crankcase heater will operate;

<p>When the compressor is off</p> Signup and view all the answers

In the schematic, the coil on line #11 does not control;

<p>The blower motor</p> Signup and view all the answers

Study Notes

Electrical Basics

  • Current flow is the movement of electrons in a circuit.
  • Impedance is the opposition to alternating current (AC).
  • Like charges repel each other, while unlike charges attract.
  • A conductor is a material that easily releases electrons.
  • Current is represented by the symbol "I".
  • Electricity can produce light, heat, and magnetism.

Electrical Components and Conductors

  • Safety ground conductors are typically colored green.
  • Electrons have a negative charge.
  • Silicon is considered the best material for use as a semiconductor.
  • An ohmmeter must use internal power to check a load or circuit.
  • A typical 24 volt, 20 ohm contactor coil in series with a 200 ohm control relay will only activate the control relay.

Circuit Calculations

  • In a parallel circuit with three 15 ohm defrost heaters connected to 120 volts, total power consumed is 2880 Watts.
  • Resistance needed in a 120 volt circuit to limit current to 2 amps is 60 ohms.
  • Resistance is defined as opposition to electron flow.
  • In electrical wiring, black wires indicate a hot conductor.

Power and Energy

  • A heater drawing 5 amps on 460 volts consumes 2300 Watts.
  • When connected in parallel, resistors maintain the same voltage drop across each as the source voltage.
  • Three resistors in parallel (R1 = 30 ohms, R2 = 15 ohms, R3 = 10 ohms) result in a total resistance of 6 ohms.
  • Watts can be calculated using the formula W = E × I.

Capacitors and Circuit Parameters

  • Capacitors are grounded in series with the start winding of motors.
  • Output voltage from transformers is dependent on primary and secondary turns; for instance, a transformer with 1000 turns on the primary and 500 on the secondary gives 60 volts output from 120 volts input.
  • Transformers increase voltage; they are rated in volt-amperes (VA) at the secondary.
  • A diode controls the direction of electron flow.

Motors and Control Devices

  • An electronically commutated motor (ECM) is designed to provide optimal airflow under varying conditions.
  • A solenoid valve operates on the principle of electromagnetism.
  • Motors are rated according to the maximum amperage they handle.
  • Thermal overload contacts in line starters are generally manually reset.

Troubleshooting and Tests

  • When diagnosing a malfunctioning A/C system, symptoms include short cycling of compressors and fans which may indicate issues with a faulty blower motor or relay.
  • A faulty thermostat may result in the inability to control fan operation correctly.
  • Understanding that a crankcase heater operates when the compressor is off is crucial in troubleshooting.
  • It is essential to discharge capacitors safely before testing with an ohmmeter.

General Electrical Principles

  • Three-phase loads require a minimum of three supply lines.
  • The correct wiring of electrical circuits is critical to prevent overloads and ensure safety.
  • The synchronous speed of a four-pole, 60 Hz motor is approximately 1800 RPM, determined by the number of stator poles.
  • The cancellation of magnetic fields in a two-wire circuit leads to zero ammeter readings.

Diagrams and Schematic Interpretation

  • Schematic diagrams outline voltage readings at various points, critical for troubleshooting.
  • The voltage across certain components can provide insights into equipment functionality and potential faults.

Capacitor Specifications

  • Capacitors have specific ratings for microfarads (MFD) and voltage; acceptable temporary replacements adhere to these specifications.
  • Capacitor analyzers check the capacitance of capacitors, determining their operational capability.

Circuit Safety

  • Circuit breakers and fuses act as shields against excessive current, preventing overload situations.
  • Understanding circuit symbols and schematic representations is crucial for recognizing components and their connections in electrical systems.

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