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⁻.