SPM Electrical & Electronics Engineering Studies flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ohm's law

For a conductor at constant temperature, voltage equals current multiplied by resistance (V = IR). It links the three fundamental circuit quantities.

Electrical power formula

Power in watts equals voltage times current (P = VI), also I²R or V²/R. It states the rate at which electrical energy is converted.

Faraday's law

A changing magnetic flux through a coil induces an electromotive force proportional to the rate of change of that flux linkage.

Capacitor energy storage

A capacitor stores energy in its electric field equal to half the capacitance times the square of the voltage across it.

SI prefix micro

The prefix micro means one millionth, or 10⁻⁶. It is used for small currents, capacitances and voltages in electronics.

Let-go current threshold

The largest current at which a person can release a gripped conductor, roughly 10–15 mA for 50/60 Hz alternating current.

Residual current device

A protective device that compares live and neutral currents and trips when the difference, indicating earth leakage, exceeds its rating.

Lock-out tag-out

An isolation procedure in which energy sources are switched off, locked and tagged so equipment cannot be re-energised during work.

Kirchhoff's current law

At any circuit node, the total current entering equals the total current leaving, expressing conservation of electric charge.

Thevenin's theorem

Any linear two-terminal network can be replaced by a single voltage source in series with a single equivalent resistance.

Maximum power transfer

A source delivers maximum power to a load when the load resistance equals the source's internal (Thevenin) resistance.

Series resonance

In an RLC series circuit, resonance occurs when inductive and capacitive reactances are equal, leaving only resistance and maximum current.

Zener diode regulation

A Zener diode operated in reverse breakdown holds a nearly constant voltage, providing simple shunt voltage regulation with a series resistor.

Bridge rectifier

Four diodes arranged so both half-cycles of AC are converted to DC, without needing a centre-tapped transformer.

Transistor saturation region

The BJT operating state where the base is driven hard enough that the collector-emitter voltage is near minimum, acting as a closed switch.

Operational amplifier gain

With negative feedback, closed-loop gain is set by external resistors, for example minus R_f divided by R_in for the inverting configuration.

Transformer turns ratio

The secondary voltage divided by the primary voltage equals the secondary turns divided by the primary turns, for an ideal transformer.

Induction motor slip

Slip is the difference between synchronous speed and actual rotor speed, expressed as a fraction of synchronous speed.

Synchronous speed formula

Synchronous speed in rev/min equals 120 times the supply frequency divided by the number of magnetic poles.

High-voltage transmission benefit

Raising transmission voltage lowers current for the same power, reducing resistive I²R losses and conductor cross-section.

Closed-loop control

A control system that measures its output, compares it with the setpoint and acts on the error to reduce deviation.

Nyquist sampling criterion

To reconstruct a signal without aliasing, the sampling rate must be at least twice the highest frequency present in it.

Frequency modulation

A modulation method in which the carrier's frequency varies with the information signal, giving good immunity to amplitude noise.

PLC scan cycle

A programmable logic controller repeatedly reads inputs, executes its stored program and updates outputs in a fixed repeating sequence.

Worst-case tolerance

The maximum deviation of a combined value equals the sum of the individual component tolerances, used in worst-case design analysis.

Bill of materials

A list of every component in a design, giving reference designator, value or part number, quantity and often supplier.

Oscilloscope probe compensation

Adjusting a probe's trimmer capacitor so a calibration square wave displays flat tops, ensuring accurate high-frequency measurement.

Conflict of interest

A situation where personal or financial interest could improperly influence professional judgement; it must be disclosed and managed.

RoHS directive

European legislation restricting hazardous substances such as lead, mercury and cadmium in electrical and electronic equipment placed on the market.

WEEE directive

European rules requiring separate collection, treatment and recycling of waste electrical and electronic equipment rather than disposal with general waste.

Insulation resistance test

A test applying a high DC voltage, typically 500 V, between conductors and earth to confirm insulation is sound, measured in megohms.

Current clamp meter

An instrument that measures current by sensing the magnetic field around a conductor, without breaking or disconnecting the circuit.

Voltage-drop testing

Measuring voltage lost across a connection or cable while current flows, revealing high-resistance faults that static resistance tests may miss.