Physics
Right-Hand Thumb Rule — Thumb = current direction, curled fingers = magnetic field direction around a straight conductor. For solenoid: curl fingers along current loops, thumb shows N-pole.
SALT for Lens/Mirror Sign Convention — S: distances measured from optical center/pole; A: above principal axis = positive height; L: light travels left-to-right; T: towards incident ray = positive for mirrors.
UV IR ROYGBIV — Increasing wavelength: Ultraviolet → Visible (Red, Orange, Yellow, Green, Blue, Indigo, Violet) → Infrared. Decreasing frequency and energy same order reversed.
Real is Inverted, Virtual is Erect — For single lens/mirror: real images always inverted; virtual images always erect. Concave mirror gives real (inverted) when object beyond F, virtual (erect) when within F.
Newton's Laws: I-BUS-CAR — I: Inertia (First Law); B: Because; U: Unbalanced force; S: Speed changes; C: Causes; A: Acceleration; R: Reaction equal-opposite (Third Law). Second Law: F=ma between first and third.
S-U-V-A-T Equations — v=u+at; s=ut+½at²; v²=u²+2as. Remember: "Some Ugly Visitors Attacked Teacher" for which variable appears where.
Specific Heat DIY — Water has highest specific heat (4200 J/kg°C), hence best coolant. Remember: "Desert Immediately hot, Yucky-cold" — land (low SH) heats/cools fast, water (high SH) changes slowly.
Ohm's Law Triangle — Draw triangle: V on top, I and R at bottom. Cover what you want: V=IR, I=V/R, R=V/I. Similarly P-V-I triangle: P=VI.
Chemistry
OIL RIG — Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons). For redox reactions: reducing agent oxidized, oxidizing agent reduced.
Reactivity Series: "Please Send Charlie's Monkeys And Zebras In Lead Cages Heavy Security Guard" — Potassium, Sodium, Calcium, Magnesium, Aluminum, Zinc, Iron, Lead, Copper, Mercury, Silver, Gold. Decreasing reactivity; left displaces right from salt solutions.
pH Memory: 7-UP — pH 7 = neutral (water). Below 7 = acidic, above 7 = basic. Each step = 10× change in H⁺ concentration (logarithmic scale).
SPDF Orbital Sequence: 1s 2s 2p 3s 3p 4s 3d... — Follow diagonal rule: 1s→2s→2p→3s→3p→4s→3d→4p→5s→4d... Or remember: (n+l) value lowest fills first; if equal, lower n fills first.
Valency Patterns in Periodic Table — Group number = valency for groups 1,2,13,14 (1,2,3,4). For 15,16,17: valency = 18–group number (3,2,1). Noble gases = 0 (group 18).
Homologous Series Formula CₙH₂ₙ₊₂ — Alkanes: CₙH₂ₙ₊₂; Alkenes: CₙH₂ₙ; Alkynes: CₙH₂ₙ₋₂. Each –CH₂– addition increases molecular mass by 14.
Acidic Radical Groups: "No Sulking Clowns Bring Beautiful Interesting New Shows" — Nitrate NO₃⁻, Sulphate SO₄²⁻, Chloride Cl⁻, Bromide Br⁻, Iodide I⁻, Carbonate CO₃²⁻.
Balancing: CHON Order — Balance Carbon first, then Hydrogen, then Oxygen, finally Nitrogen and others. Saves time in organic combustion reactions.
Biology
Kingdom Classification: "King Philip Came Over For Good Soup" — Kingdom, Phylum, Class, Order, Family, Genus, Species. Taxonomic hierarchy from broadest to most specific.
Mitosis Phases: PMAT — Prophase, Metaphase, Anaphase, Telophase. Remember: "People Meet And Talk". Meiosis has PMAT twice (Meiosis I and II).
Plant Tissues:EMAP — Meristematic, Epidermal, Muscular (wrong—actually Ground), Vascular. Better: "Mighty Emperor Makes Arrangements Perfectly" — Meristematic, Epidermal, Parenchyma, Collenchyma, Sclerenchyma, Xylem, Phloem.
Enzyme Suffix "-ase" — Enzyme named after substrate + "ase": Amylase (starch), Protease (protein), Lipase (lipid), Sucrase (sucrose). Quick identification in digestion questions.
Photosynthesis: "6-6-1 Upstairs" — 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Needs light and chlorophyll. Remember: oxygen comes from water splitting, not CO₂.
Mendel's Law Memory: DISS — Dominance, Independent assortment, Segregation. Monohybrid ratio 3:1 (F₂), dihybrid 9:3:3:1. Test cross reveals genotype (cross with homozygous recessive).
Reflex Arc Path: SRIRME — Stimulus → Receptor → Sensory neuron → Interneuron (spinal cord) → Relay → Motor neuron → Effector (muscle/gland). No brain involvement = faster response.
Mathematics
BODMAS/PEMDAS — Brackets, Orders (powers), Division, Multiplication, Addition, Subtraction. Common trap: Division and Multiplication are equal priority (left to right), same with Addition and Subtraction.
Divisibility Rules Quick — 3: digit sum divisible by 3; 4: last 2 digits by 4; 6: even AND divisible by 3; 8: last 3 digits by 8; 9: digit sum by 9; 11: alternating digit sum difference by 11.
Quadratic Formula: "A Negative Boy, B, Minus His Square Root..." — x = [−b ± √(b²−4ac)] / 2a. For quick factoring, check if discriminant (b²−4ac) is perfect square.
Coordinate Plane Quadrants: All Students Take Classes — Starting top-right, going counter-clockwise: Q1 (+,+), Q2 (−,+), Q3 (−,−), Q4 (+,−). Signs of (x,y) coordinates.
Triangle Congruence: SSS-SAS-ASA-AAS-RHS — Side-Side-Side, Side-Angle-Side, Angle-Side-Angle, Angle-Angle-Side, Right-Hypotenuse-Side. AAA only proves similarity, not congruence.
Arithmetic Progression Formulas — nth term: aₙ = a + (n−1)d. Sum: Sₙ = (n/2)[2a + (n−1)d] or (n/2)(first + last). Remember: "Average of first and last, times number of terms."
Circle Theorems: ATAP — Angle in semicircle = 90°; Tangent perpendicular to radius; Angle at center = 2× angle at circumference (same arc); Perpendicular from center bisects chord.
Probability: 0 to 1 Range — P(event) = favorable/total outcomes. P(sure event) = 1, P(impossible) = 0. P(A) + P(not A) = 1