REE Board Exam key terms

A complex quantity whose magnitude is the root-mean-square value of a sinusoid and whose angle is its phase, allowing steady-state AC circuits to be solved with algebra.

A number of the form a + bi, where a and b are real numbers and i is the imaginary unit with i squared equal to minus one; used for impedance and phasor calculations.

A way of expressing a complex number as a magnitude and an angle, written r angle theta, which makes multiplication, division, and phase calculations straightforward.

A single number computed from the entries of a square matrix that indicates whether the matrix can be inverted and is used in solving simultaneous linear equations.

A method of solving simultaneous linear equations in which each unknown is found as the ratio of two determinants, one formed by replacing a column with the constants.

An integral transform that converts a time-domain function into a function of the complex frequency s, turning differential equations into algebraic equations that are easier to solve.

The algebraic process of rewriting a complicated rational expression as a sum of simpler fractions, commonly used to convert a Laplace transform back into the time domain.

A representation of a periodic waveform as a sum of sine and cosine terms at integer multiples of the fundamental frequency, showing the harmonic content of the signal.

The instantaneous rate at which one quantity changes with respect to another, equal to the slope of the tangent to its curve; used to describe transients and to find extreme values.

The accumulated value of a function between two limits, interpreted as the signed area under its curve; used to obtain charge from current and energy from power.

The statement that the net force acting on a body equals its mass multiplied by its acceleration, linking force, mass, and motion in mechanical systems.

The internal force per unit area developed within a material when external loads act on it, commonly expressed in pascals or megapascals.

The fractional change in a dimension of a material, calculated as the change in length divided by the original length; it is a dimensionless quantity.

The principle that, within the elastic limit, stress is directly proportional to strain, with the constant of proportionality being the modulus of elasticity.

An energy relation for steady incompressible flow stating that pressure, kinetic energy per unit volume, and elevation energy per unit volume sum to a constant along a streamline.

A dimensionless ratio of inertial forces to viscous forces in fluid flow that indicates whether the flow is laminar, transitional, or turbulent.

The quantity of heat needed to raise the temperature of one unit mass of a substance by one degree, used in calorimetry and energy balance calculations.

A thermodynamic property that measures how dispersed energy is within a system; it increases in irreversible processes and stays constant in reversible adiabatic ones.

A logarithmic index of hydrogen ion concentration equal to the negative base-ten logarithm of that concentration, indicating whether a solution is acidic, neutral, or basic.

The concentration of a solution expressed as the number of moles of solute dissolved per liter of solution, widely used in stoichiometry and electrolysis problems.

The principle that the mass of a substance deposited or released at an electrode is proportional to the charge passed, with one faraday (about 96,485 coulombs) liberating one mole of a monovalent species.

The ratio of real power to apparent power in an alternating-current circuit, equal to the cosine of the phase angle between voltage and current.

The product of root-mean-square voltage and root-mean-square current in an AC circuit, measured in volt-amperes, combining real and reactive power.

The power that oscillates back and forth between the source and reactive elements such as inductors and capacitors without producing net work, measured in volt-amperes reactive.

The total opposition a circuit offers to alternating current, combining resistance and reactance into a complex quantity measured in ohms.

A method of expressing power-system voltages, currents, and impedances as fractions of chosen base values, simplifying calculations and removing transformer ratios from the equivalent circuit.

A technique that resolves an unbalanced three-phase set of voltages or currents into three balanced sets called positive, negative, and zero sequence for fault analysis.

The abnormally large current that flows when a low-impedance path bypasses the normal load, limited only by source voltage and system impedance.

The change in output voltage of a transformer or generator from no load to full load, expressed as a percentage of the full-load voltage.

The ratio of primary turns to secondary turns in a transformer, which determines the ratio of voltages and the inverse ratio of currents.

The speed of the rotating magnetic field in an AC machine, equal to 120 times the frequency in hertz divided by the number of poles, in revolutions per minute.

The difference between synchronous speed and actual rotor speed of an induction motor, usually stated as a percentage of synchronous speed.

The maximum continuous current a conductor can carry without exceeding its rated temperature, depending on material, insulation, cross-sectional area, and installation conditions.

A luminous discharge around a high-voltage conductor caused by ionization of surrounding air when the surface voltage gradient exceeds the breakdown strength of air.

The ratio of average load to maximum demand over a given period; a high value indicates that equipment is used efficiently.

The intentional connection of electrical equipment or a circuit point to earth, providing a low-impedance path for fault current and limiting dangerous voltage rise.

A resettable switching device that automatically opens a circuit during overload or fault current and extinguishes the arc to interrupt the current safely.

A device that continuously monitors current, voltage, or other quantities and sends a trip command to a circuit breaker when it detects an abnormal condition.

Voltages or currents at integer multiples of the fundamental frequency that distort the waveform and cause extra heating and losses in electrical equipment.

The total real power delivered by a balanced three-phase system, equal to the square root of three times line voltage times line current times power factor.