AC Fundamentals 241
AC Fundamentals 241 discusses alternating current (AC) as the most common form of electrical power. AC waves can be viewed and measured on the screen of an oscilloscope. Alternating current is economical, can be sent long distances, and can be stepped up or stepped down to adjust voltage. Different AC waveforms exist, the most common being sine waves. Ohm's law holds true for AC circuits, but voltage and current both increase and decrease together in a cycle while impedance remains constant.
Anyone working within electrical systems must understand the fundamental concepts and basic workings of alternating current to ensure their safety. After taking this course, students will be able to describe electrical flow in an alternating current circuit and the impact alternating current has on electrical variables.

Difficulty Intermediate

Format Online

Number of Lessons 18

Language English
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 Alternating Current
 How AC Flows
 The Advantages and Disadvantages of AC
 The AC Generator
 Measuring AC
 AC Basics Review
 Common AC Waveforms
 Sine Wave Characteristics
 Sine Wave Values
 The Sine Function
 AC Generation and Wave Characteristics Review
 Root Mean Square
 AC Circuits and Impedance
 Ohm's Law
 Frequency and Period
 Types of AC Power
 True Power and Linear Loads
 AC Features Review
 Distinguish AC from DC.
 Describe the flow of AC.
 List the advantages and disadvantages of AC.
 Describe how a generator creates AC.
 Describe how oscilloscopes measure AC.
 Identify the different types of AC waveforms.
 Describe sine wave characteristics and terminology.
 Describe different sine wave variable values.
 Explain the sine function.
 Describe RMS.
 Describe the relationship between basic AC circuits and impedance.
 Describe the variables of Ohm's law.
 Distinguish between frequency and period.
 Describe the different types of AC power.
 Describe how to produce true power in AC.
AC
Alternating current. Current that reverses direction at regularly recurring intervals of time. AC usually alternates 60 times per second, or 60 hertz, in the U.S.
active power
The result of both current and voltage reaching their peaks simultaneously. Active power, also called true power, is a measurement of the rate at which electricity performs work such as producing heat, light, or mechanical energy.
alternating current
AC. Current that reverses direction at regularly recurring intervals of time. Alternating current usually alternates 60 times per second, or 60 hertz, in the U.S.
alternator
A device that generates AC. Alternators produce this current through the use of a mechanical device such as an engine or a motor.
amp
A unit of measurement that indicates the amount of current flowing in a circuit. Amp is short for ampere.
amplitude
A measurement of the size of a wave. Amplitude is also referred to as magnitude.
amplitude
A measurement of the size of a wave. Amplitude measures the intensity of a signal.
angle of rotation
The position and direction of the circular motion that is used to produce voltage in a sine wave. The angle of rotation affects electrical variables.
apparent power
The combination of both true power and reactive power. Apparent power is the product of voltage in an AC circuit multiplied by all current flowing through the circuit system.
armature
A device found in generators that has many separate coils wound around it. An armature rotates in the generator and creates a magnetic field that produces direct current.
average value
The mean value of all of the AC values during one AC cycle. Average value is a result of the RMS value.
battery
A device that converts chemical energy to electrical energy. Batteries are a source of DC.
capacitive load
An AC electrical load in which the current wave reaches its peak before the voltage wave. Capacitive load values can be calculated using the impedance formula.
capacitive reactance
The opposition in the capacitor to voltage changes. The value of capacitive reactance is required to calculate impedance in an AC circuit.
capacitor
C. A device that stores current. Capacitors release current when it is needed in a circuit.
cathoderay oscilloscope
CRO. The earliest analogbased oscilloscope. Cathoderay oscilloscopes do not always display waves in a traditional representation, requiring users to do more work to interpret their readings.
circuit
A completely enclosed path of electrical current consisting of various devices. Electrical circuits usually include a source, path, load, and control.
conductor
A wire that allows for the easy flow of electricity. Conductors move in a magnetic field and produce voltage.
constants
A value, factor, or number that does not change. In AC circuits, impedance is a constant.
cycles
One complete revolution or rotation. In AC, a cycle is considered to be a completed 360° waveform.
cyclical
Charactertized by repetitive action. One complete AC cycle is 360 electrical degrees.
DC
Direct current. Current that flows in one direction. Direct current does not reverse the direction of flow.
degrees
Units of measurement for angles and circular motion. Degrees express the amount of rotation in a sine wave.
digital storage oscilloscopes
DSO. A device that produces a digital visual display of a voltage or current wave shape. Digital oscilloscopes are more commonly used than analog versions because they require less interpretation by users.
direct current
DC. Current that flows in one direction. Direct current is the less common form of current.
effective value
An AC value that is given as the equivalent of a DC value. An effective value is the value that AC would have to produce to have the same effect as a DC 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.
electric current
The flow or movement of charged particles. Electric current can flow in two different ways within a circuit.
electrical degrees
Units of measurement for expressing the amount of rotation in a generator. Electrical degrees describe the position in an AC sine wave.
electromagnetic induction
The process in which current is generated by a magnetic field using a currentcarrying coil. Electromagnetic induction produces current in an AC generator.
electrons
A negatively charged particle that orbits the nucleus of an atom. Electrons flow between atoms to cause electricity.
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 energy by magnetic induction. Generators create AC power and sine waves.
hertz
Hz. A unit of measurement indicating a single cycle in an alternating current. Sixty Hz is the most common frequency for a given electrical outlet in the U.S.
impedance
Z. A measure of reactance and resistance in an AC circuit. Impedance is calculated to measure the total opposition to current flow in an AC circuit.
in phase
The state in which current and voltage reach their peaks at the same time in alternating current. When current and voltage are in phase, true power occurs.
inductive load
An AC electrical load in which the voltage wave reaches its peak before the current wave. Inductive load values can be calculated using the impedance formula.
inductive reactance
The opposition in the inductor to current flow. The value of inductive reactance is required to calculate impedance in an AC circuit.
inductor
L. A device that opposes changes in current flow. Inductors store energy as a magnetic field.
LC circuits
A type of AC circuit that includes a power source that is connected to an inductor and a capacitor. LC circuits can be used to tune radio stations.
linear load
An AC electrical load in which both current and voltage waves reach their peak simultaneously. Linear loads are necessary to achieve maximum efficiency.
linear wave
A waveform that is graphically represented with straight lines. The voltage of a linear wave rises at a constant rate with time.
load
A component in a circuit that converts electricity into light, heat, or mechanical motion. Loads may include light bulbs, appliances, or machines.
magnetic field
A force of attraction that surrounds magnets and currentcarrying conductors. Magnetic fields cause electromagnetic induction.
magnetic flux
The force that surrounds a magnet and exhibits the powers of attraction and repulsion. Magnetic flux is described as imaginary lines of force that exit the magnet's north pole and return to its south pole.
magnitude
A measurement of the size of a wave. Magnitude is also referred to as amplitude.
magnitude
The size of a wave. Magnitude is the highest positive point on the wave and the maximum positive voltage value.
negative peak value
The lowest negative point on a wave. Negative peak value is equal to the lowest voltage of the wave.
ohm
A unit of measurement of electrical resistance. Ohms multiplied by amperes equals volts as stated by Ohm's law.
Ohm's law
The law describing the relationship between amperage, voltage, and resistance. Ohm's law states that volts equals amperes multiplied by ohms.
oscillators
Devices that produce a continuous string of on/off pulses at a preset frequency. Oscillators produce square waves.
oscilloscope
A device that produces a visual trace of a voltage or current wave shape. Oscilloscopes are used to view AC and DC waves graphically.
peak
The highest amplitude value on a wave. The peak of a wave can be negative or positive.
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. Peak negative voltage indicates the maximum negative pressure of the wave.
peak positive voltage
The highest positive point on a wave. Peak positive voltage indicates the maximum positive pressure of the wave.
peaktopeak value
A measurement from the negative peak value to the positive peak value. Peaktopeak value is determined by adding the positive peak amplitude to the negative peak amplitude.
period
The reciprocal value of frequency. A period measures the amount of time for one cycle to be completed.
phase angle
A measurement that is used to represent the inefficiency in an AC circuit. The phase angle is used on the power triangle to explain the relationship between the different types of AC power.
polarity
A state of opposites. Polarity involves the north and south attractions of a magnet and the positive and negative changes in a circuit.
pole
Either of two oppositely charged ends of a magnet. The relationship of the poles causes magnetic flux.
positive peak value
The highest positive point on a wave. Positive peak value is equal to the highest voltage of the wave.
power
The amount of work accomplished within a given period of time. Power is the product of current and voltage and is measured in watts.
power supply
A device that provides DC power to a circuit. Power supplies often must convert AC to DC.
power triangle
A graphic representation of the relationship between the three different types of AC power and the phase angle. The power triangle is used to calculate total power in a circuit.
RC circuits
A type of AC circuit that includes a power source connected to a resistor and a capacitor. RC circuits can be used as filters for current.
reactance
X. A measure of how difficult it is for current to move through an inductor. Reactance is a factor when calculating impedance in an AC circuit.
reactive power
Power that is required to produce magnetic fields. Reactive power is often described as stored power because it does not produce work.
reciprocal
The inverse of a given value. A reciprocal is equal to 1 divided by the number.
resistance
A measure of how difficult it is for current to move through a conductor. Resistance is a factor when calculating impedance in an AC circuit.
resistor
R. A device that restricts current flow. Resistors produce work, such as heat, light, or mechanical motion.
RL circuits
A type of AC circuit that includes a power source that is connected to a resistor and an inductor. RL circuits can be used as DC power supplies.
RLC circuits
A type of AC circuit that includes a power source connected to a resistor,an inductor, and a capacitor. RLC circuits are used to tune radios and audio receivers.
root mean square
RMS. The effective value of AC. RMS is the value that AC would have to produce to have the same effect as a DC value and is determined using the 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. Sawtooth waves rise and fall in straight lines.
sine
In a right triangle, the ratio of the side opposite an angle to the longest side 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
SIN. The ratio of the length of the opposite side to the length of the longest side of a right triangle. The sine of the angle of rotation is used to find the voltage of a sine wave.
sine function
The act of determining the ratio of the length of the opposite side to the length of the longest side of a right triangle. The sine function is used to find the voltage of a sine wave.
sine wave
The most common type of AC waveform. Sine waves consist of 360 electrical degrees and are produced by rotating machines.
sine waves
The most common type of AC waveform. A sine wave consists of 360 electrical degrees.
slip ring
A conductive device attached to the end of a generator rotor that conducts current to the brushes. Slips rings are also used in AC wound rotor motors.
square wave
AC waveforms that have squared peaks. Square waves are produced by oscillators.
stepped down
A phrase used to describe voltage adjustment in electricity. When voltage is stepped down, it has been decreased.
stepped up
A phrase used to describe voltage adjustment in electricity. When voltage is stepped up, it has been increased.
test probe
A device attached to a measuring instrument. Test probes send the electrical signal being measured to the oscilloscope.
total power
The full amount of power in an AC circuit. Total power takes into account true power, reactive power, and apparent power.
transformers
A device that transfers electrical energy from one circuit to another without changing the frequency. Transformers are most often used to change line voltage.
triangle wave
A type of AC waveform that appears as repeating triangles. The voltage for a triangle wave rises and falls at a constant rate.
trigonometry
The branch of mathematics that addresses the measurements and relationships of a triangle and its parts. AC circuit calculations require knowledge of trigonometry.
trigonometry
The branch of mathematics that addresses the measurements and relationships of a triangle and its parts. Knowledge of trigonometry is required to make AC circuit calculations.
true power
The result of both current and voltage reaching their peaks simultaneously. True power, also called active power, is a measurement of the rate at which electricity performs work such as producing heat, light, or mechanical energy.
variables
Factors in electricity that change according to the situation. Variables in AC circuits include voltage, current, and resistance.
volt
A unit of measurement that indicates the amount of electromagnetic force, also called pressure, in a circuit. Volts measure voltage.
voltage
A measure of electrical pressure or potential known as electromotive force. Voltage is measured in volts.
voltage drops
The amount of energy used by a device with resistance in the circuit. Voltage drops are experienced with both AC and DC.
voltamperes
VA. A unit of electrical power that measures apparent power. Voltamperes are equal to the product of a single volt and a single ampere.
voltamperes reactive
VAR. A unit of electrical power that measures reactive power. Voltamperes reactive is the product of the apparent power multiplied by the sine of the phase angle between voltage and current.
volts
A measure of electrical pressure or potential known as electromotive force. Volts measure voltage.
watts
A unit of measurement that indicates the amount of electrical power present in a circuit or device. Watts require a change in energy to exist.
waveforms
The type or shape of wave produced by AC. Waveforms depend upon the angle at which a rotating armature cuts through lines of magnetic flux.
wavelengths
The distance between separate peaks of a sine wave. AC produces wavelengths of both current and voltage.
waves
A graphic representation of the flow of alternating current. Wave shapes depend on the method by which the current is produced.
work
The result of electricity flowing through resistance. Work appears in the form of heat, light, or mechanical energy or motion.