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Questions and Answers
What is the most commonly used form of electricity?
What device converts mechanical energy into electrical energy?
Generator
What does alternating current refer to?
Constant reversing of polarities
The positions of a sine wave include the ______, ______, and ______.
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What is the measurement of one cycle per second?
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What is a single-phase current?
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In a three-phase system, how must the phases be spaced?
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What converts electrical energy to rotating mechanical energy?
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What is a commutator?
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What are the stationary windings of a motor called?
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Which of the following is a conducting connection to physical earth?
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What provides a fault path for current during a ground fault?
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What color is a ground wire typically? One way to identify is ______.
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List three reasons for having a ground wire:
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What is the purpose of grounding?
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What is identified by 1.Handle, 2.Heel, 3.Lip, 4.Shoe?
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What is a raceway?
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The LFMC must be secured every ______ and within ______ of a termination point.
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Study Notes
Alternating Current
- Most prevalent form of electricity used in various settings including homes and industries.
- Originates from power plants and is essential for residential, industrial, and commercial applications.
Source of AC
- Generators convert mechanical energy to electrical energy, in contrast to motors.
- Operating on a rotating mechanism, they produce electrical current stored as electricity.
Characteristics of AC
- Alternating current involves the constant reversal of polarities, depicted by a sinusoidal wave (sine wave).
Sine Wave Structure
- Consists of three key positions: positive peak, negative peak, and neutral point.
Frequency
- Defined as the number of cycles per second, measured in hertz.
- One complete cycle corresponds to 360 degrees.
Single Phase
- Current generated is concentrated on one phase or sine wave.
- Commonly found voltages include 120 volts and 240 volts, typically used for central air conditioning systems.
Three Phase System
- Requires three currents spaced exactly 120 degrees apart.
- In a 480 volt three-phase system, the voltage reading from a leg to ground is 277 volts.
Motors
- Convert electrical energy into rotating mechanical energy.
- Function based on the principles of magnetism, with alternating poles causing rotation.
Commutator
- Series of bands connecting armature coils to brushes.
- Allows for the reversal of electrical current direction.
Stator
- The fixed part of a motor, made up of the core, windings, and coils.
- Comprised of two main components: stator coils and stator core.
Brushes
- Comprise a sliding contact, usually made from carbon and copper, that maintains conductivity with the commutator.
- Essential for transferring electricity to a revolving armature.
Motor Types
- Series Wound Motor: Current flows through both armature and field windings, adjusting speed based on load conditions and capable of starting under heavy loads.
- Parallel Wound Motor (Shunt Motor): Current divides between armature and field windings, maintaining constant speed despite varying loads.
Grounding
- Ground provides a conductive connection to the earth for safety.
- Grounding conductors offer a fault path for current in the event of a ground fault.
Ground Fault
- Occurs when a current-carrying conductor directly contacts the earth.
Importance of Grounding
- Protects individuals and equipment from electrical faults.
- Requires specific identification methods for ground wires: green with yellow stripe, green, or bare copper.
Ground Wire Specifications
- Ground wires must match the size of the largest conductor used, with the possibility of using two sizes smaller.
Raceways
- Enclosed channels for holding various electrical conductors, adhering to code specifications.
Installation Rules for EMT
- No more than 360 degrees of bends between pull points; all bends must be counted.
- Raceways must be fully installed before conductor installation.
Rigid Metal Conduit
- Thick-walled conduit, ideal for hazardous areas, requiring secure placement every 10 feet and within 3 feet of termination.
Electrical Metallic Tubing (EMT)
- Commonly used tubing, requiring secure installation every 10 feet and within 3 feet of termination points; fittings available, easy to bend, and not threaded.
Flexible Metal Conduit
- Also known as "flex," requires securing every 4.5 feet and within 12 inches of termination points.
Liquidtight Flexible Metal Conduit
- Known as SEALTITE, suitable for outdoor and humid applications, adhering to a 360-degree bend rule.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Prepare for your final exam with these flashcards focusing on alternating current (AC). Each card covers essential concepts such as the definition of AC and its sources, along with their applications and functions in various settings. Perfect for reinforcing your knowledge and ensuring success on the test.
