UPPSC AE Mechanical key terms

A principle stating that the entropy of an isolated system never decreases and that heat cannot flow spontaneously from a colder body to a hotter body, limiting the efficiency of all heat engines.

A thermodynamic property measuring the degree of disorder or unavailable energy in a system; it increases in all real irreversible processes and stays constant in ideal reversible ones.

An ideal reversible cycle of two isothermal and two isentropic processes operating between a hot and a cold reservoir; it sets the maximum possible efficiency for any heat engine.

The ratio of net work output to heat supplied in a power cycle, usually expressed as a percentage; it indicates how much input heat is converted into useful work.

An idealised process that proceeds through a continuous series of equilibrium states and can be exactly reversed, leaving no net change in the system or surroundings.

The internal resisting force per unit area developed within a material when it is subjected to external loads, commonly measured in newtons per square millimetre or megapascals.

The fractional change in length or shape of a body produced by applied stress, a dimensionless quantity calculated as change in dimension divided by original dimension.

The ratio of tensile or compressive stress to the corresponding strain within the elastic limit of a material; it measures stiffness and is denoted by E.

The negative ratio of lateral strain to longitudinal strain when a material is stretched or compressed within its elastic range; typical metals show values near 0.3.

A graphical construction on a shear-stress versus normal-stress plane used to determine principal stresses, maximum shear stress, and stress on any inclined plane at a point.

The normal stress acting on a plane where the shear stress is zero; these maximum and minimum normal stresses are used to predict failure in machine components.

A dimensionless ratio of inertial forces to viscous forces in a flow, used to predict whether flow is laminar or turbulent; low values indicate laminar flow.

A relation for steady, incompressible, frictionless flow stating that pressure energy, kinetic energy per unit volume, and potential energy per unit volume remain constant along a streamline.

A smooth, orderly fluid motion in which layers slide past one another without mixing; it typically occurs at low Reynolds numbers and is described by Poiseuille's law in pipes.

The operating sequence of a reciprocating engine comprising intake, compression, power, and exhaust strokes, completing one thermodynamic cycle in two crankshaft revolutions.

The ratio of the total cylinder volume when the piston is at bottom dead centre to the clearance volume when at top dead centre; it strongly affects engine efficiency.

A manufacturing process in which molten metal is poured into a mould cavity and allowed to solidify, producing a part whose shape follows the mould geometry.

A fabrication process that joins materials by coalescence, usually achieved by heat, pressure, or both, with or without a filler metal.

The duration a cutting tool remains usable before reaching a defined wear criterion; it is related to cutting speed by Taylor's tool life equation.

A device that automatically regulates the speed of an engine by controlling the supply of working fluid in response to changes in load, maintaining near-constant speed.

A rotating mass attached to a shaft that stores kinetic energy and releases it during periods of higher demand, reducing speed fluctuations within a single cycle.

The amount of heat removed from a refrigerated space per unit time or per unit mass of refrigerant; it forms the numerator of the coefficient of performance.

The ratio of useful refrigeration or heating effect to the work input for a refrigeration or heat pump cycle; higher values indicate greater energy efficiency.

The basic freedoms guaranteed to citizens by Part III of the Indian Constitution, enforceable through writs under Article 32 and Article 226 of the Constitution.

Guidelines in Part IV of the Indian Constitution directing the State to promote social and economic welfare; they are not directly enforceable in courts.

Eleven obligations listed in Article 51A of the Indian Constitution, added by the 42nd Amendment, urging citizens to respect the Constitution and national symbols.

The introductory statement of the Indian Constitution declaring the source of authority, the nature of the State, and its objectives of justice, liberty, equality, and fraternity.

The system of local self-government in rural India established by the 73rd Constitutional Amendment, operating at village, block, and district levels.

A seasonal reversal of wind direction that brings heavy rainfall to the Indian subcontinent, driven by differential heating of land and sea and the shift of the ITCZ.

An intense low-pressure storm system forming over warm tropical oceans, characterised by high-speed rotating winds and heavy rain, known regionally as a cyclone or hurricane.

A period of increased agricultural output in India during the 1960s and 1970s resulting from high-yielding seed varieties, irrigation, fertilisers, and mechanisation.

दो वर्णों या ध्वनियों के मेल से उत्पन्न परिवर्तन को संधि कहते हैं; जैसे विद्या + आलय = विद्यालय, जहाँ आ + आ मिलकर आ हो जाता है।

संधि द्वारा जुड़े हुए शब्दों को पुनः उनके मूल रूपों में अलग-अलग करके लिखने की प्रक्रिया, जिससे संधि का प्रकार स्पष्ट होता है।

दो या दो से अधिक शब्दों के मेल से बने संक्षिप्त पद को समास कहते हैं; इसमें पदों के बीच के विभक्ति चिह्न लुप्त हो जाते हैं।

काव्य या गद्य में सौंदर्य, चमत्कार और प्रभाव उत्पन्न करने वाले तत्व को अलंकार कहते हैं; यह शब्दालंकार और अर्थालंकार दो प्रकार का होता है।

साहित्य में पाठक या श्रोता के हृदय में उत्पन्न होने वाली आनंदमयी अनुभूति को रस कहते हैं; श्रृंगार, हास्य, करुण आदि इसके प्रमुख भेद हैं।

A grammatical construction in which the subject performs the action of the verb, as in 'The engineer designed the pump'; it is usually clearer and more direct than the passive.

A construction in which the subject receives the action of the verb and the doer is either mentioned in a by-phrase or omitted, as in 'The pump was designed by the engineer'.

The reporting of a speaker's exact words inside quotation marks, as in 'He said, "I am busy"'; it contrasts with indirect or reported speech.

A fixed expression whose meaning cannot be deduced from the literal meanings of its individual words, such as 'break the ice' meaning to start a conversation.

A single word that replaces a longer descriptive phrase, such as 'omnipotent' for one who is all-powerful; a common vocabulary item in objective English tests.