# AC Fundamentals 210

This class introduces the concept of alternating current (AC) and describes the variables that measure AC power.

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## Class Details

Class Name:
AC Fundamentals 210
Description:
This class introduces the concept of alternating current (AC) and describes the variables that measure AC power.
Version:
1.0
Difficulty:
Intermediate
Number of Lessons:
15
Spanish
Related 2.0 Class:
AC Fundamentals 241

## Class Outline

• Objectives
• What Is Alternating Current?
• The Oscilloscope
• How AC Flows
• Common AC Waveforms
• The AC Generator
• Sine Wave Characteristics
• Current, Voltage, and Impedance in AC
• Frequency and Period
• Using the Sine Function
• Measuring Sine Waves
• Root Mean Square (RMS)
• Power in AC
• Summary

## Objectives

• Distinguish AC from DC.
• List the advantages of AC.
• Describe uses of an oscilloscope.
• Describe the flow of AC.
• Identify types of AC waveforms.
• Describe how a generator creates AC.
• Identify sine wave measurements throughout its cycle.
• Describe Ohmâ€™s Law variables in AC.
• Distinguish between frequency and period.
• Describe how the sine function is used for AC calculations.
• Describe amplitude and its related values.
• Describe RMS value.
• Describe how to produce true power in AC.

## Certifications

SME
• CMfgT
MSSC
• MSSC Maintenance Awareness

## Glossary

Vocabulary Term Definition
algebra A branch of math that uses known quantities to find unknown quantities. In algebra, letters are sometimes used in place of numbers.
alternating current Current that regularly reverses the direction of its flow in a repeating, cyclical pattern.
amplitude A measurement of the size of a wave. Amplitude is also referred to as magnitude.
anode An electrical terminal that usually carries a positive electrical charge.
armature The rotating portion of a generator that passes through magnetic fields to generate current.
brushes Stationary conductive devices which contact the slip rings on each end of the armature. The brushes conduct AC to the load so the current can perform work.
capacitive load An AC electrical load in which the current wave reaches its peak before the voltage.
cathode An electrical terminal that usually carries a negative electrical charge. An oscilloscope uses a cathode at the end of a cathode ray tube, which heats up and emits electrons.
cathode ray tube An analog display device using a vacuum tube that generates images on a layer of phosphors driven by an electron beam.
constant A variable that remains unchanging.
cycle A single increment of something that occurs repeatedly. AC flows in cycles of 360 electrical degrees.
cyclical Characterized by a cycle. One complete AC cycle is 360 electrical degrees.
degree A unit of measurement for angles and circular motion. Degrees expresses the amount of rotation in a sine wave.
direct current Current that travels in one direction. Direct current does not reverse the direction of flow.
effective value A DC value that is given as the equivalent of an AC value. An effective value is the value that DC would have to produce to have the same effect as an AC value.
efficiency A measure of the energy output of a system versus the total energy supplied to it. Maximum efficiency is achieved with a linear load.
electrical degree A unit of measurement for expressing the amount of rotation in a generator and the position in an AC sine wave.
electromagnetic induction The process in which current is induced in a magnetic field using a current-carrying coil. An AC generator uses electromagnetic induction.
frequency A measurement of the number of complete AC cycles that occur in one second. Frequency is measured in Hertz (Hz).
generator A device that converts mechanical energy into electrical power.
Hertz The unit used to measure frequency. Hertz expresses the number of complete AC cycles per second.
impedance The resistance to current flow in an AC circuit.
in phase The phrase used to describe a linear load. AC is described as "in phase" when both waves reach their peak simultaneously.
inductive load An AC electrical load in which the voltage wave reaches its peak before the current.
linear load An AC electrical load in which both current and voltage waves reach their peak simultaneously. Also referred to as "in phase", linear loads are necessary to achieve maximum efficiency.
linear wave A waveform that is graphically represented with straight lines. A triangle wave is an example of a linear wave.
load A component in a circuit that converts electricity into light, heat, or mechanical motion. Examples of loads are a light bulb, an appliance, or a machine.
magnetic field A force of attraction that surrounds magnets and current-carrying conductors.
magnetic flux The area in and around a magnet that exhibits the powers of attraction and repulsion. Rotating an armature through lines of magnetic flux induces AC.
magnitude The size of a wave. Graphically, magnitude is the highest positive point on the wave and is the maximum positive voltage value.
maximum voltage The highest voltage value that a given wave reaches. The maximum voltage is equal to the peak amplitude of a wave.
negative peak value The lowest negative point on a wave. The negative peak value is equal to the lowest voltage of the wave.
oscillator An electronic device that generates a high frequency.
oscilloscope A device that produces a visual trace of a voltage or current wave shape, generally on a cathode ray tube. AC waves can be viewed graphically on an oscilloscope.
peak The highest or lowest point on a wave.
peak amplitude The highest amplitude value on a wave. Peak amplitude can be negative or positive.
peak negative voltage The lowest negative point on a wave. The peak negative voltage indicates the maximum negative voltage of the wave.
peak positive voltage The highest positive point on a wave. The peak positive voltage indicates the maximum positive voltage of the wave.
peak-to-peak value A measurement from the negative peak value to the positive peak value.
period The reciprocal value of frequency. Period measures the amount of time for one cycle.
phosphorescent screen A type of screen that uses phosphorous to project an electron beam. An oscilloscope uses a phosphorescent screen to project graphic representations of AC waveforms.
polarity Having two oppositely charged poles, one positive and one negative. Polarity determines the direction in which current tends to flow.
pole One of two ends of the axis of a sphere. Poles also refer to the opposite ends of a magnet.
positive peak value The highest positive point on a wave. The positive peak value is equal to the highest voltage of the wave.
power The amount of work accomplished within a given period of time. With electricity, power is the product of current and voltage and is measured in watts.
power factor A ratio of the average power available and the actual amount of power used. Power factor is an indication of efficiency.
reciprocal The inverse of a given value. The reciprocal is equal to 1 divided by the number.
ripple Characterized by a varying value. Unlike the constant values of DC, the average value of an AC output constantly ripples.
RMS An abbreviation for root mean square. RMS is the formula used to determine the effective value of an AC sine wave.
root mean square The effective value of AC. RMS is the value that DC would have to produce to have the same effect as an AC value and is determined using the root mean square (RMS) formula.
root-mean-square formula The formula used to determine the effective value of an AC sine wave. RMS is equal to the peak value multiplied by 0.707.
sawtooth wave A type of AC waveform that is produced by electronic test devices. The sawtooth wave rises and falls in straight lines.
sine In a right triangle, the ratio of the side opposite an angle and the hypotenuse of the triangle. In AC, the voltage of a sine wave is equal to the peak voltage multiplied by the sine of the angle of rotation.
sine wave The most common type of AC waveform. A sine wave consists of 360 electrical degrees and is produced by rotating machines.
slip ring A conductive device attached to the end of an armature that conducts current to the brushes.
square wave A type of AC waveform that is produced by an oscillator. As voltage changes, current changes direction in the square wave.
stepped down In electricity, a phrase used to describe voltage adjustment. To step down voltage means to decrease voltage.
stepped up In electricity, a phrase used to describe voltage adjustment. To step up voltage means to increase voltage.
triangle wave A type of AC waveform that is linear. The voltage for a triangle wave rises at a constant rate with time.
trigonometry The branch of mathematics that addresses the measurements and relationships of a triangle and its parts. AC circuit calculations require knowledge of trigonometry.
true power The result of both current and voltage reaching their peak simultaneously. True power is a measurement of the rate at which electricity performs work such as producing heat, light, or mechanical energy.
vacuum The absence of matter. A cathode ray tube contains a vacuum with a cathode and one or more anodes.
voltage drop The amount of voltage needed to push a given amount of current through a given amount of resistance.
wave A graphic representation of the flow of alternating current. The shape of an AC wave depends on the method by which the current was produced.
waveform The type or shape of wave produced by AC. Waveform depends upon the angle which a rotating armature cuts through lines of magnetic flux.