ISRO Scientist Electrical key terms

A two-terminal linear network reduced to a single voltage source in series with a resistance, where the source equals the open-circuit voltage and the resistance is measured with all independent sources set to zero.

In a linear circuit with multiple independent sources, the total response in any branch equals the algebraic sum of responses produced by each source acting alone, with other independent sources deactivated.

A linear two-terminal network modeled as a current source in parallel with a resistance, where the current is the short-circuit current and the resistance matches the Thevenin resistance.

The frequency at which a circuit's inductive and capacitive reactances cancel, making the impedance purely resistive; for a series RLC network it equals one over two pi root LC.

A dimensionless measure of resonator selectivity, equal to the ratio of stored energy to energy dissipated per cycle, or the resonant frequency divided by the half-power bandwidth.

The range of frequencies between the half-power points of a resonant or filter response, where output amplitude falls to roughly 0.707 of its maximum value.

A set of matrix coefficients (Z, Y, h, or ABCD) relating input voltage and current to output voltage and current of a network, used to cascade and analyze interconnected stages.

A two-port network whose input and output ports are interchangeable without changing port currents and voltages, implying equal diagonal elements in its Z or Y parameter matrix.

The temporary behavior of a circuit or system between the instant an input or disturbance is applied and the moment steady-state conditions are reached, governed by natural frequencies and initial conditions.

The interval after which a first-order exponential response decays to about 36.8 percent of its initial value, equal to resistance times capacitance or inductance divided by resistance.

Power dissipated as heat by circulating currents induced in a magnetic core by alternating flux; it rises with the square of frequency and flux density and is reduced by thin laminated or ferrite cores.

Energy lost per cycle as the magnetic domains of a core reverse magnetization, proportional to the area of the B-H loop and to frequency, and minimized by using soft magnetic materials.

A model that represents a transformer's winding resistance, leakage reactance, magnetizing branch, and core-loss branch, usually referred to one side for voltage regulation and efficiency calculations.

The percentage change in secondary terminal voltage when full load is removed while the primary supply voltage and frequency are held constant, indicating how well a transformer holds its output.

The fractional difference between synchronous speed and actual rotor speed of an induction machine, expressed as a fraction or percentage and essential for computing rotor frequency and torque.

The rotational speed of the rotating magnetic field, equal to 120 times supply frequency divided by the number of poles, and the speed at which a synchronous machine runs at steady state.

The curve relating electromagnetic torque of an induction motor to slip, showing starting torque, maximum (breakdown) torque, and the near-linear stable operating region at small slip.

The effective reactance of a synchronous machine armature winding that accounts for armature reaction and leakage flux, used in the phasor model to relate terminal voltage and internal emf.

The phase angle between the internal excitation emf and the terminal voltage of a synchronous machine; it determines the air-gap power transferred, which varies as the sine of this angle.

A normalization method in which voltages, currents, powers, and impedances are expressed as fractions of chosen base values, simplifying transformer ratios and fault calculations across voltage levels.

A technique that resolves an unbalanced three-phase set of phasors into positive, negative, and zero sequence balanced sets, enabling separate analysis of unsymmetrical faults and unbalanced loads.

The maximum short-circuit apparent power a network can deliver at a given point, equal to nominal voltage times short-circuit current, used to select switchgear breaking capacity.

A protective relay that estimates the impedance between its location and a fault from measured voltage and current, tripping when the impedance falls within a set zone characteristic.

A switching device that makes and breaks load and fault currents and extinguishes the arc between contacts, rated by breaking capacity, making capacity, and short-circuit duration.

A protective device that clamps overvoltages by diverting surge current to earth through a nonlinear element and then restores high impedance at normal operating voltage.

The ratio of the Laplace transform of a system output to that of its input under zero initial conditions, describing the system's dynamics independently of the input signal.

A graphical map of the roots of a system's denominator (poles) and numerator (zeros) in the complex s-plane, whose positions reveal stability and response speed.

An algebraic test on the coefficients of a characteristic polynomial that determines the number of closed-loop poles in the right half-plane without explicitly solving for the roots.

A pair of logarithmic frequency-response graphs showing magnitude in decibels and phase in degrees versus frequency, used to assess gain margin and phase margin of a feedback system.

A stability test that relates the number of encirclements of the minus-one point by the open-loop frequency response to closed-loop right-half-plane poles.

The fraction of each switching period during which a semiconductor switch conducts; it sets the ideal voltage conversion ratio of choppers and switched-mode converters.

A technique that varies switch on-time within a fixed period to synthesize an average voltage or current, widely used for inverter voltage control and harmonic shaping.

The ratio of the root-sum-square of all harmonic components to the fundamental component of a waveform, expressed as a percentage of the fundamental.

The process by which current transfers from one conducting device or phase to another, such as from a thyristor to the next in a converter or from a brush to a commutator segment.

The near-zero differential input voltage of an ideal operational amplifier in negative feedback, causing the inverting input to track the non-inverting input potential without a physical connection.

The maximum rate of change of an amplifier output voltage, usually quoted in volts per microsecond, which limits large-signal high-frequency performance.

The minimum intervals before and after an active clock edge during which a flip-flop data input must remain stable for reliable capture, defining timing constraints in synchronous digital circuits.

A bandlimited signal must be sampled at more than twice its highest frequency component to be reconstructed without aliasing, setting the minimum sampling rate for digital processing.

The false low-frequency component that appears when a signal is sampled below the Nyquist rate, making distinct frequencies indistinguishable after reconstruction.

The discrete-time counterpart of the Laplace transform, converting a sequence into a function of a complex variable to analyze stability and response of sampled-data systems.

A tabular arrangement of characteristic-polynomial coefficients built row by row to count right-half-plane roots and reveal marginal stability conditions.

The tendency of alternating current to concentrate near the surface of a conductor, raising effective resistance and reducing internal inductance as frequency increases.

A partial electrical breakdown of air near high-voltage conductors where the local field exceeds the breakdown strength, causing power loss, audible noise, and radio interference.

A scalar by which an eigenvector is scaled when a square matrix multiplies it; eigenvalues determine system stability and natural modes in state-space models.

A nonzero vector whose direction is unchanged by multiplication with a square matrix, only scaled by the corresponding eigenvalue.

An integral transform converting a time-domain function into the complex s-domain, turning linear differential equations into algebraic equations for easier solution.

An iterative numerical technique that updates a guess using the function value divided by its derivative, converging quadratically near a simple root of an equation.

A measure of how an algorithm's running time grows with input size, commonly expressed in big-O notation to compare scalability of alternative solutions.

A linear data structure with last-in first-out access, supporting push and pop at one end, used for recursion, expression evaluation, and backtracking.

A search algorithm that repeatedly halves a sorted array by comparing the target with the middle element, achieving logarithmic time complexity.

The comparison of two quantities by division and the statement of equality between two such comparisons, used to solve mixture, partnership, and scaling problems quickly.

A quantitative aptitude topic where rates of doing work are added for combined effort, with the total work often set to the least common multiple of completion times.