AC Fundamentals 241

AC

Alternating current. Electricity that reverses direction at regularly recurring intervals of time. AC powers the electric grid.

adjacent side

The shorter side of a right triangle that is located next to the reference angle. The adjacent side and the hypotenuse form the reference angle.

alternating current

AC. Electricity that reverses direction at regularly recurring intervals of time. Alternating current powers the electric grid.

alternators

A device that generates AC. Alternators produce this current through the use of a mechanical device such as an engine or a motor.

ammeters

A device that measures amperes in electrical circuits. Ammeters can calculate the effective value of a sine wave.

amperage

A measurement of the amount of current flowing in a circuit. Amperage is measured in amperes (A).

amperes

A. A unit of measurement that describes both an amount of electricity and the time it takes to travel a certain distance. Amperes measure amperage and are also called amps.

amplitude

The vertical distance between the zero centerline and the maximum positive or negative value of a wave. Amplitude is half of the peak-to-peak value.

analog

A continuously variable electrical signal. Analog oscilloscopes use a cathode ray tube to display voltage waves.

angle of rotation

A measurement that indicates the position of an alternating current wave in its cycle. The angle of rotation is measured in electrical degrees.

apparent power

S. The total power supplied by the source in an alternating current circuit. Apparent power is measured in volt-amperes.

armature

A component found in generators that consists of many coils of conducting wire. Armatures can be stationary or rotating depending on the type of generator.

capacitance

The ability of a capacitor to store charge. Capacitance is impacted by the phase of an alternating current cycle.

capacitive load

An alternating current load that uses an electrostatic field to store electrical energy. Capacitive loads cause amperage waves to peak before voltage waves.

capacitor

C. A device that resists a change in voltage, preventing surges or spikes. Capacitors use conductors to store energy in an electric field.

circuit

A completely enclosed path for electrical current. Circuits usually include a source, path, load, and control.

coils

A length of conducting wire in which a voltage is induced. Coils typically contain many turns, or loops, of wire.

conductor

A material or element that allows free movement of electrons and therefore allows easy flow of electricity. Conductors are typically metals.

constant

A fixed number in an equation used to determine unknown variables. A constant is required to determine the effective value of an AC circuit.

cosine

The ratio of the side adjacent to the reference angle of a right triangle to the triangle's longest side, or hypotenuse. Cosine can be used to calculate the power factor of an alternating current circuit.

current

The flow of electricity. Current strength is called amperage and is measured in amperes (A).

cycles

The process of alternating current going from zero to its peak positive value, back to zero, to its peak negative value, and then back to zero. One complete AC cycle equals 360 electrical degrees.

DC

Direct current. Electricity that travels in one direction. DC is less commonly used than alternating current.

digital electronics

A device that processes and controls digital signals. Digital electronics produce square waves.

digital storage oscilloscopes

DSOs. A device that produces a digital visual display of a voltage wave. Digital storage oscilloscopes are more commonly used than analog oscilloscopes because they require less interpretation by users.

direct current

DC. Electricity that travels in one direction. Direct current is less commonly used than alternating current.

effective value

The alternating current value that would produce the same heating effect as direct current. Effective value, which is also referred to as the root mean square, involves taking the square root of the average of all the squared wave values.

electric grid

A network of electrical connections used to transfer electricity from a central source to multiple points of use. The electric grid distributes alternating current.

electrical degrees

A unit of measurement for expressing the amount of rotation in a generator. One electrical degree represents 1/360th of a full cycle of an alternating current waveform.

electrical testing instruments

A device used to measure and analyze electrical variables. Electrical testing instruments include voltmeters and oscilloscopes.

electromagnetic force

The attraction and repulsion a magnet exerts on other charged objects. Electromagnetic force causes electrons to move in a conductor.

electromagnets

A magnet that gains an attractive force only when current passes through it. An electromagnet is typically formed by wrapping a current-carrying coil around a pole piece.

electrons

A negatively charged particle that orbits the nucleus of an atom. The flow of electrons between atoms produces electricity.

electrostatic field

The area of potential electrical force surrounding an object. Electrostatic fields store energy for capacitive loads.

field coils

An electromagnet that rotates to produce a magnetic field. In a rotating field generator, field coils turn instead of the armature.

field windings

A coil of conducting wire connected to the armature that energizes the pole pieces. Field windings are connected to a stationary armature in a rotating field generator.

frequency

The number of complete alternating current cycles completed in one second. Frequency is measured in hertz (Hz).

generators

A device that converts mechanical energy into electrical energy by magnetic induction. Generators create AC power and sine waves.

heating effect

The amount of heat generated by electricity when it passes through resistive elements. The heating effect can impact how efficiently a machine runs.

hertz

Hz. A unit of frequency equal to one cycle per second. The hertz is used to measure how often the direction of alternating current reverses.

hypotenuse

The side of a right triangle that is located opposite the right angle. The hypotenuse is always the longest side of the triangle.

impedance

The total amount of resistance in an alternating current circuit. Ohm's Law for AC circuits states that impedance can be calculated by dividing the RMS amperage value by the RMS voltage value.

inductance

The ability of an electrical conductor to change amperage in nearby conductors using electromotive force. Inductance only occurs in alternating current systems, not direct current systems.

inductive load

An alternating current load that uses a magnetic field generated by electricity to store electrical energy. Inductive loads cause voltage waves to peak before amperage waves.

inductor

L. A device that resists a change in amperage, preventing surges or spikes. Inductors consist of a coil of conducting wire that creates a magnetic field when current passes through it.

in-phase

A condition that occurs when waves reach their peak positive and peak negative values simultaneously. In-phase waves produce more efficient power than out-of-phase waves.

instantaneous value

The measurement of voltage or amperage in an alternating current wave at one particular moment. Instantaneous values can be anywhere between zero and the peak value.

lagging

A positive power factor that occurs when amperage falls behind voltage. Lagging power factors occur in circuits with inductive loads.

LC circuits

An AC circuit that includes an inductor and a capacitor. LC circuits can be used to tune radio stations.

leading

A negative power factor that occurs when amperage is ahead of voltage. Leading power factors occur in circuits with capacitive loads.

linear wave

A waveform that is graphically represented with straight, symmetrical lines because voltage or amperage immediately decrease or increase after reaching the peak value. The voltage or amperage of a linear wave rises and falls at a constant rate over time.

lines of flux

Imaginary lines of force that surround a magnet. Lines of flux form a magnetic field.

load

A component in a circuit that converts electricity into light, heat, or mechanical motion. Examples of loads include light bulbs, appliances, and machines.

magnetic field

The area in and around a magnet in which a magnetic force exists. Magnetic fields exhibit the powers of attraction and repulsion.

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.

magnetic induction

The use of magnets to produce voltage in a conductor. Magnetic induction occurs whenever a conductor passes through magnetic lines of flux.

motor

A machine that converts one form of energy, such as electricity, into mechanical energy or motion. Electric motors operate on the principle of magnetic induction.

multimeters

A device that combines the functions of an ammeter, a voltmeter, and an ohmmeter. Multimeters can calculate the effective value of a sine wave.

negative charge

An electrical charge with a surplus of electrons. Electrons flow from a negative charge to a positive charge.

Ohm's Law

The universal truth that describes the relationship between amperage, voltage, and resistance. For AC circuits, Ohm's Law uses impedance instead of resistance.

opposite side

The side of a right triangle that is located across from the reference angle. The measurement of the opposite side helps determine the dimensions of the hypotenuse and adjacent side.

oscilloscope

An electrical testing instrument that displays a visual representation of a voltage waveform. Oscilloscopes can also measure amperage with accessories.

out-of-phase

A condition that occurs when waves reach their peak positive and peak negative values at a different time. Out-of-phase are not as efficient as in-phase waves.

peak negative value

The lowest negative point on a wave. Peak negative value is the maximum negative voltage or amperage of the wave.

peak positive value

The highest positive point on a wave. Peak positive value is the maximum voltage or amperage of the wave.

peak value

The maximum positive or negative value of an alternating current wave's voltage or amperage. Peak values are important for various waveform calculations.

peak-to-peak value

The vertical distance between the negative peak value and the positive peak value of a wave. Peak-to-peak value is determined by adding the peak positive value to the peak negative value.

period

The time required for an AC wave to complete one full cycle. Period is the reciprocal value of frequency and is measured in seconds per cycle.

phase

The position of a wave that indicates how far along its cycle has progressed. Phases are measured in electrical degrees.

phase angle

A measurement that is used to represent the inefficiency of out-of-phase waves in an AC circuit. Phase angle is measured in degrees.

polarity

Having two oppositely charged poles, one positive and one negative. Polarity determines the direction in which current flows.

pole pieces

A magnet in a device such as a generator that helps create the magnetic field. Pole pieces facilitate magnetic induction.

positive charge

An electrical charge with a shortage of electrons. Electrons flow from a negative charge to a positive charge.

power factor

PF. The ratio of real power to apparent power. Power factor helps determine a circuit's efficiency.

power factor correction

The process of compensating for lagging or leading amperage by adding capacitors and/or inductors. Power factor correction can significantly improve the efficiency of a system.

power source

The component of a circuit that supplies it with electrical energy. Power sources, like a generator, can provide energy for one or multiple loads.

power triangle

The graphic representation of the relationship between the three different types of AC power and the phase angle. The power triangle is used to calculate the different types of power in an alternating current circuit.

probes

A component attached to an electrical testing instrument that uses a conductive tip to connect to an electrical component. Probes must be physically connected to the circuit being tested to measure the signal.

Pythagorean theorem

A mathematical rule that describes the relationship between the sides of a right triangle. The Pythagorean theorem states that the sum of the squares of the adjacent and opposite sides equals the square of the hypotenuse.

ratio

The relationship between two quantities sometimes expressed as a fraction. Ratios in right triangles can help determine important alternating current values.

RC circuits

An AC circuit that includes a resistor and a capacitor. RC circuits can be used to filter current.

reactance

X. The opposition generated in changing magnetic fields and electrostatic fields by inductors and capacitors in an alternating current circuit. Reactance affects the rate of current flow.

reactive power

Q. The power that flows between inductors and capacitors in an alternating current circuit. Reactive power is measured in volt-amperes reactive.

real power

P. The power used to perform real work, such as producing heat, light, or mechanical motion, in an alternating current circuit. Real power is measured in watts (W).

reciprocal

The inverse of a given value. The reciprocal of a value is equal to 1 divided by the value.

reference angle

A measured or known angle used to label the sides of a right triangle. The reference angle cannot be triangle's right angle.

resistance

R. The opposition to current flow. Resistance is measured in ohms (Ω).

resistive circuits

A circuit that contains only resistive components. Resistive circuits generate the ideal power factor of one.

resistive load

An alternating current load that produces heat using resistors. Resistive loads are seen in appliances such as light bulbs and heaters.

resistor

R. A device that limits the amount of current flow. Resistors produce work, such as heat, light, or mechanical motion.

right triangle

A triangle containing exactly one 90° angle. Right triangles help determine different variables for alternating current waveforms.

RL circuits

An AC circuit that includes a resistor and an inductor. RL circuits can be used as DC power supplies.

RLC circuits

An AC circuit that includes a resistor, inductor, and capacitor. RLC circuits are used to tune radios and audio receivers.

RMS

Root mean square. A calculation that involves taking the square root of the average of all the squared set of values. RMS, which is also referred to as the effective value, is used to calculate the amount of voltage or amperage required for AC to produce the same heating effect as DC.

robotics

A field of science that focuses on programmable mechanical devices. Robotics may use digital electronics that produce square waves.

root mean square

RMS. A calculation that involves taking the square root of the average of all the squared set of values. Root mean square, which is also referred to as the effective value, is used to calculate the amount of voltage or amperage required for AC to produce the same heating effect as DC.

rotating field generators

A generator that uses a stationary armature and a revolving magnetic field. Rotating field generators are the most common type of alternating current generators.

sawtooth wave

An alternating current waveform that has asymmetrical angled peaks. Sawtooth waves are produced by electrical testing instruments.

seconds per cycle

A unit of measurement for determining the number of seconds it takes for one AC cycle to occur. Seconds per cycle measures the period of a wave.

semiconductors

A material or device that restricts electrons but still allows them to flow. Semiconductors may produce triangle waves depending on the type.

sine

The ratio of the opposite side of a triangle to the hypotenuse. The sine of the angle of rotation is used to find the instantaneous value of a sine wave.

sine wave

An alternating current waveform with a curved shape. Sine waves, also known as sinusoidal waves, are the most common waveforms and are produced by alternators and generators.

sinusoidal wave

An alternating current waveform with a curved shape. Sinusoidal waves, also known as sine waves, are the most common waveforms and are produced by alternators and generators.

square root

A mathematical function that indicates which unknown number is multiplied by itself one time. The square root of the instantaneous values of an AC wave gives the root mean square value.

square wave

An alternating current waveform that has squared peaks. Square waves are produced by digital electronics with clock signals.

stepped down

Transformed to a lower voltage. AC can be stepped down, but DC cannot be transformed effectively.

stepped up

Transformed to a higher voltage. AC can be stepped up, but DC cannot be transformed effectively.

terminal

A connecting point in a circuit to which a wire can be attached to connect a component. A terminal has either a negative or positive charge.

tone generators

A device that converts electrical signals into audio signals. Tone generators produce triangle waves.

transformers

A device that uses mutual induction to transfer electrical energy from one circuit to another without changing the frequency. Transformers are most often used to increase and decrease voltage.

triangle wave

An alternating current waveform that has symmetrical triangular peaks. Triangle waves are produced by semiconductors and tone generators.

trigonometry

The branch of mathematics that deals with the measurements and relationships of triangles and their parts. Trigonometry is used to make AC circuit calculations.

unity power factor

The ideal power factor of 1.0, which indicates voltage and amperage are in phase and all power is being converted into real work. The unity power factor only occurs in purely resistive circuits.

voltage

A measure of electrical pressure or potential known as electromotive force. Voltage is measured in volts (V).

voltage drop

A decrease in voltage along a conductor through which electricity flows. Voltage drops occur whenever electricity passes through resistance.

volt-amperes

VA. A unit used to measure apparent power. One volt-ampere is equal to one volt multiplied by one ampere.

volt-amperes reactive

VAR. A unit used to measure reactive power. Volt-amperes reactive is used to measure when amperage and voltage are not in-phase in an alternating current circuit.

voltmeters

A device used to measure the voltage of an electrical circuit. Voltmeters can calculate the effective value of a sine wave.

volts

V. A unit of measurement for electrical pressure or potential known as electromotive force. Volts measure voltage.

watts

W. A unit of measurement that indicates the amount of electrical power used in or produced by a circuit. A circuit uses one watt when one volt forces one amp through a load.

waveforms

The shape of a wave produced by an alternating current signal. Waveforms vary based on the method used to produce current.

waves

A graphic representation of the flow of alternating current. Wave shapes depend on the method used to produce the current.

work

The result of electricity flowing through resistance in a circuit. Work appears in the form of heat, light, or motion.