THDC JE cheat sheet

Concrete mix nominal grades: M5 (1:5:10), M7.5 (1:4:8), M10 (1:3:6), M15 (1:2:4), M20 (1:1.5:3), M25 (1:1:2) by volume cement:sand:aggregate; M25 and above require design mix as per IS 10262.

Standard cube test: 150 mm cubes, 28-day compressive strength; characteristic strength fck is the value below which no more than 5% of results fall.

Slump test measures workability of concrete; compaction factor test is used for low-workability mixes where slump is unsuitable.

Ohm's law V = IR; power P = VI = I²R = V²/R. For three-phase systems: P = √3·V_L·I_L·cos φ, where cos φ is the power factor.

Transformer EMF equation: E = 4.44·f·Φm·N (RMS); turns ratio N1/N2 = V1/V2 = I2/I1 for an ideal transformer.

Synchronous speed of an induction motor: Ns = 120f/P (rpm), where f is supply frequency in Hz and P is the number of poles; slip s = (Ns − Nr)/Ns.

Carnot efficiency of a heat engine: η = 1 − T2/T1 with absolute temperatures; no real engine between the same reservoirs can exceed it.

For a simply supported beam with central point load W and span L: maximum bending moment = WL/4 at midspan; maximum shear force = W/2 at supports.

Op-amp ideal characteristics: infinite open-loop gain, infinite input impedance, zero output impedance, infinite bandwidth; the inverting amplifier gain is −Rf/Rin and the non-inverting gain is 1 + Rf/Rin.

Percentage change: successive changes of a% and b% give a net change of a + b + ab/100 percent (signs matter).

Simple interest SI = PRT/100; compound interest amount A = P(1 + R/100)^T, and CI = A − P.

Speed–time–distance: Distance = Speed × Time; for a train of length L crossing a platform of length P, time = (L + P)/Speed.

Boats: downstream speed = u + v, upstream speed = u − v, where u is boat speed in still water and v is stream speed.

Average of n numbers = sum/n; if a group of average A1 and size n1 mixes with average A2 and size n2, combined average = (n1A1 + n2A2)/(n1 + n2).

Work: if A finishes a job in x days and B in y days, together they take xy/(x + y) days; work rate is the reciprocal of time.

Profit and loss: Profit% = (SP − CP)/CP × 100; when two articles are sold at the same price with equal profit% and loss%, there is always a net loss of (x/10)² percent.

Permutation vs combination: nPr = n!/(n − r)!; nCr = n!/[r!(n − r)!]; nCr = nC(n − r).

Ratio and mixture: alligation rule gives the ratio of mixing as (mean price − cheaper price) : (dearer price − mean price).

Series with squares, cubes, or primes: check differences (first, second, third order) before assuming a pattern; alternating series often combine two independent rules.

Coding–decoding: letter positions A=1 to Z=26; opposite letters sum to 27 (A↔Z, B↔Y, C↔X, etc.).

Blood relations: use a family tree with gender markers; 'maternal uncle' is mother's brother, 'paternal aunt' is father's sister.

Direction sense: draw a compass with N up; a right turn from North faces East, a left turn from North faces West; net displacement uses Pythagoras for perpendicular moves.

Syllogism: 'All A are B' does not imply 'All B are A'; only conclusions that hold in every possible Venn diagram are valid.

Seating arrangement: for a circle of n people facing the centre, the person to the immediate left is clockwise; facing outward reverses the direction.

Analogy and classification questions rely on the relationship type (part–whole, cause–effect, worker–tool); identify the relation before choosing the pair.

Number and letter series in matrix form: check row-wise and column-wise patterns separately, then look for a diagonal rule.

Indian Constitution: adopted 26 November 1949, came into force 26 January 1950; Dr B. R. Ambedkar chaired the Drafting Committee.

Fundamental Rights are in Part III (Articles 12–35); Directive Principles of State Policy are in Part IV (Articles 36–51).

The President is the constitutional head of state; the Prime Minister heads the real executive; Article 74 provides for the Council of Ministers to aid and advise the President.

THDC India Limited is a joint venture of the Government of India and the Government of Uttar Pradesh, incorporated in 1988, headquartered at Rishikesh, Uttarakhand.

The Tehri Hydro Power Complex on the Bhagirathi river in Uttarakhand includes the Tehri Dam, Koteshwar Dam, and the Tehri Pumped Storage Plant.

RBI is India's central bank (established 1935, nationalised 1949); it controls monetary policy, and the repo rate is the rate at which banks borrow from RBI.

National parks and rivers: Corbett National Park lies in Uttarakhand on the Ramganga; the Ganga originates at Gangotri (Gaumukh) and the Yamuna at Yamunotri.

SI base units: length metre, mass kilogram, time second, electric current ampere, temperature kelvin, amount mole, luminous intensity candela.

Track national energy targets: India aims for 500 GW of non-fossil capacity by 2030 and net-zero emissions by 2070, announced at COP26 in Glasgow.

Know the major hydro and pumped-storage projects: Tehri (Uttarakhand), Koyna (Maharashtra), Sardar Sarovar (Gujarat), Nathpa Jhakri (Himachal Pradesh).

Space and defence milestones: Chandrayaan-3 soft-landed near the lunar south pole in August 2023; Aditya-L1 is India's solar observatory mission.

International groupings: G20, BRICS, SCO, QUAD; India hosted the G20 summit in New Delhi in 2023.

Economic terms in the news: GDP, CPI (retail inflation), WPI, fiscal deficit (target expressed as a percentage of GDP), and GST slabs.

Sports and awards: the Arjuna Award, Khel Ratna, and Dronacharya Award are given for sportspersons, outstanding performers, and coaches respectively.

Environment conventions: UNFCCC, the Paris Agreement (2015), and the Kyoto Protocol; the IPCC assesses climate science.

For current-affairs questions, verify the year and the exact title of the scheme or mission; similar-sounding names are common distractors.

Subject–verb agreement: a singular subject takes a singular verb; with 'either…or' and 'neither…nor', the verb agrees with the nearer subject.

Articles: 'a' before consonant sounds, 'an' before vowel sounds (an hour, a university); 'the' for unique or already-mentioned nouns.

Tenses: present perfect (has/have + past participle) for past actions with present relevance; past perfect (had + past participle) for the earlier of two past actions.

Prepositions of time: 'in' for months, years, seasons; 'on' for days and dates; 'at' for exact times and night/noon.

Active to passive: object becomes subject, verb becomes be + past participle, and the doer is introduced by 'by' (e.g., 'He wrote a letter' → 'A letter was written by him').

Direct to indirect speech: change the reporting verb and shift tense back one step, adjusting pronouns and time/place words (now → then, today → that day).

Common confusions: 'affect' (verb) vs 'effect' (noun); 'principal' (chief/school head) vs 'principle' (rule); 'complement' vs 'compliment'.

Idioms: 'at the eleventh hour' means at the last moment; 'a bolt from the blue' means a sudden shock; 'to burn the midnight oil' means to study or work late.

Memory hierarchy from fastest to slowest: registers, cache (L1/L2/L3), RAM, secondary storage (SSD/HDD), then offline storage; cache is faster but smaller than RAM.

1 byte = 8 bits; 1 KB = 1024 bytes, 1 MB = 1024 KB, 1 GB = 1024 MB, 1 TB = 1024 GB in binary convention.

OSI model has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, Application; TCP works at the Transport layer and IP at the Network layer.

IP address: IPv4 is 32-bit (four octets), IPv6 is 128-bit; DNS resolves domain names to IP addresses.

Common shortcuts: Ctrl+C copy, Ctrl+V paste, Ctrl+X cut, Ctrl+Z undo, Ctrl+Y redo, Ctrl+S save, Ctrl+P print, Alt+Tab switch windows.

MS Excel: a formula starts with '='; $A$1 is an absolute reference, A1 is relative, and $A1 / A$1 are mixed references.

Malware types: virus (attaches to files), worm (self-replicating over networks), trojan (disguised as legitimate software), ransomware (encrypts data for payment).

Generations of computers: first (vacuum tubes), second (transistors), third (integrated circuits), fourth (microprocessors), fifth (AI-based).