GCE A/L Engineering Technology key terms

A drawing method that shows a three-dimensional object as separate two-dimensional views, each looking straight at one face, arranged so width, height and depth line up between views.

A projection convention in which the object sits between the observer and the plane of projection, so the view seen from the front is placed on the far side, used widely in Europe and Asia.

A projection convention in which the plane of projection lies between the observer and the object, so each view is placed on the same side as the observer looking at that face.

A view projected onto a plane parallel to a slanted face, used to show the true shape and size of surfaces that appear foreshortened in the principal views.

A drawing in which part of the object is imagined cut away and the cut surface is filled with hatching, revealing internal features such as holes, bores and cavities.

The total permissible variation in a dimension, being the difference between the upper and lower limits within which a manufactured feature must fall to function correctly.

A system of standardised upper and lower sizes and clearance or interference relationships between mating holes and shafts, allowing parts made independently to assemble as intended.

A symbolic language on drawings that specifies permitted deviation in form, orientation, location and runout of features, together with the datums from which those deviations are measured.

A theoretically exact reference plane, axis or point on a part from which dimensions and geometric tolerances are measured during manufacture and inspection.

The controlled smoothness of a machined surface, usually specified as a roughness average value in micrometres and indicated on drawings by a tick symbol with a number.

The internal intensity of force within a material, calculated as applied load divided by cross-sectional area and expressed in newtons per square millimetre or pascals.

The fractional change in length of a material under load, found by dividing the change in length by the original length and having no units.

The ratio of tensile stress to tensile strain while a material behaves elastically, indicating its stiffness; a steep slope on the stress-strain graph means a stiff material.

The stress at which a material begins to deform permanently, so that the strain is no longer fully recovered when the load is removed.

The maximum stress a material withstands before it starts to neck and fail, read as the highest point on a tensile stress-strain curve.

The ability of a material to be stretched into wire or drawn out permanently without fracture, commonly measured by the percentage elongation or reduction in area at failure.

The tendency of a material to fracture with little or no plastic deformation, so that it fails suddenly rather than bending or stretching first.

A material's resistance to local indentation, scratching or abrasion, measured by tests such as Brinell, Vickers or Rockwell and linked to wear resistance.

Controlled heating and cooling of a metal to change its internal structure, used to soften, harden, stress-relieve or toughen it without altering its chemical composition.

A metallic material made by combining a base metal with one or more other elements to improve properties such as strength, corrosion resistance or hardness, for example steel or brass.

A material formed from two or more distinct constituents, such as fibres in a resin matrix, so that the combined properties exceed those of the individual components.

A single force that produces the same effect on a body as all the individual forces acting together, found by vector addition.

The state of a body when the vector sum of all forces and the sum of all moments acting on it are both zero, so it stays at rest or moves at constant velocity.

The turning effect of a force about a point, equal to the force multiplied by the perpendicular distance from the point to the line of action.

A sketch of a body showing only the external forces and moments acting on it, with supports replaced by their reaction forces, used to set up equilibrium equations.

The turning moment produced by a force acting at a distance from an axis, commonly applied to shafts and rotating machinery and measured in newton metres.

The relationship stating that the current through a conductor is directly proportional to the potential difference across it and inversely proportional to its resistance, at constant temperature.

Two rules for circuit analysis: the sum of currents entering a junction equals the sum leaving, and the algebraic sum of voltage drops around any closed loop is zero.

The opposition a component offers to the flow of electric current, measured in ohms and depending on material resistivity, length and cross-sectional area.

The cosine of the phase angle between voltage and current in an alternating-current circuit, equal to true power divided by apparent power and always between zero and one.

The total opposition to alternating current from resistance and reactance combined, expressed in ohms as a complex quantity with magnitude and phase angle.

The principle that energy cannot be created or destroyed in a closed system, only transferred as heat or work, so the change in internal energy equals heat supplied minus work done.

A thermodynamic property combining internal energy with the product of pressure and volume, useful for analysing steady-flow processes such as boilers, turbines and heat exchangers.

A measure of the disorder of a system and of the energy no longer available to do useful work; it increases in any real spontaneous process.

The ratio of useful work or heat output obtained from a device to the energy input supplied to it, usually expressed as a percentage.

The movement of thermal energy from a hotter region to a cooler one by conduction, convection or radiation, continuing until thermal equilibrium is reached.

A manufacturing process in which molten metal is poured into a mould cavity and allowed to solidify, producing complex shapes that would be difficult to machine.

Removing material from a workpiece as chips using a cutting tool on a machine such as a lathe, milling machine or drill, to achieve accurate size and finish.

A permanent joining process in which the mating surfaces of two parts are fused together, with or without added filler metal, to form a continuous bond.

The range within which the true value of a measured quantity is expected to lie, accounting for instrument limits, random scatter and systematic errors in the measurement.

The process of comparing an instrument's readings against a known reference standard and adjusting it so that its output is accurate across its working range.

The change in an instrument's output for a given change in the measured quantity, indicating how small a variation it can detect.

A control system that measures the actual output, compares it with the desired set point and uses the error to adjust the input continuously.

Returning a portion of a system's output to its input so that the system can correct itself; negative feedback stabilises, positive feedback reinforces change.

Concrete containing steel bars placed where tensile forces occur, combining concrete's compressive strength with steel's tensile strength to resist bending.

The permanent, static weight of a structure's own components such as slabs, beams, walls and finishes, which the structure must carry throughout its life.

The variable load a structure carries in service from occupants, furniture, vehicles or stored goods, estimated from design codes according to the building's use.

The ratio of a material's or structure's failure strength to the maximum load or stress expected in service, providing a margin against uncertainty and overload.

Producing technical drawings with software, using layers, precise coordinate input, blocks and dimension tools to create accurate, editable and reusable drawing files.

A named, switchable level in a CAD drawing that groups related geometry and controls its colour, line type and visibility, keeping drawings organised and easy to edit.

A named group of CAD objects stored as a single reusable unit that can be inserted many times, so that editing the definition updates every instance.

A bar chart showing project activities against a calendar timescale, making start dates, durations, overlaps and progress easy to see and compare.

The longest sequence of dependent activities through a project network, which fixes the shortest possible completion time; any delay on it delays the whole project.

A significant, clearly identifiable point in a project schedule, such as completion of a design review or handover, used to track progress without consuming time itself.

A systematic process of identifying hazards, judging the likelihood and severity of harm, and recording the control measures needed to reduce risk to an acceptable level.

Clothing and equipment worn or held by a worker to protect against specific hazards, such as helmets, goggles, gloves and safety footwear; it is the last line of defence.

A formal written authorisation issued before high-risk work begins, recording the hazards, precautions and responsible persons, and confirming that isolation and checks are complete.

A safety procedure in which energy sources are physically locked in the off position and tagged with the operator's name before maintenance, preventing unexpected start-up.

The standards of honesty, competence, public safety and fair dealing expected of engineers, including declaring conflicts of interest and refusing to certify work they cannot verify.

A documented set of recommended procedures and technical rules, often issued by a standards body or professional institution, that guides safe and consistent engineering work.