Physics
Fleming's Left Hand Rule — Thumb = thrust/Force, First finger = Field (magnetic), seCond finger = Current. Point them perpendicular; quick direction recall for motors.
VIBGYOR for EM Spectrum — Violent Rajas Make Indians Uneasy; Xavier Gets Caught = Radio, Microwave, Infrared, Visible, UV, X-ray, Gamma (increasing frequency/energy order).
Right-Hand Thumb Rule — Thumb shows current direction, curled fingers show magnetic field lines around a straight conductor. Essential for Biot-Savart and Ampère's law problems.
Lens Formula Sign Convention — Object side = negative, image side = positive; distances measured from optical center. Convex lens f positive, concave negative.
LC Oscillation Frequency — f = 1/(2π√LC). Remember "Like a Clock" swings at frequency depending on L and C for resonance circuits.
Radioactive Decay N = N₀e^(-λt) — After one half-life t₁/₂, exactly half remains; after two half-lives, one-quarter remains. Quick mental calculation trick for decay problems.
XL increases, XC decreases — Inductive reactance XL = 2πfL rises with frequency; capacitive reactance XC = 1/(2πfC) falls with frequency. Opposite behaviors for AC circuits.
Chemistry
HONC 1234 Rule — Hydrogen forms 1 bond, Oxygen 2, Nitrogen 3, Carbon 4 in stable organic molecules. Quick valency check for structure drawing.
LEO says GER — Loss of Electrons = Oxidation; Gain of Electrons = Reduction. Instant recall for redox reactions and electrochemistry.
Lucas Test Reactivity — 3° alcohol reacts immediately (turbidity in minutes), 2° in 5 minutes, 1° doesn't react at room temperature with Lucas reagent (ZnCl₂/HCl).
s-p-d-f Orbital Shapes — s = Sphere, p = dumb-bell/Peanut, d = Double dumb-bell, f = Flower-like (complex). Memorize for electron configuration and hybridization.
Aufbau: 1s 2s 2p 3s 3p 4s 3d — Diagonal rule: follow n+l value increasing order. When equal, lower n fills first. Essential for electronic configuration.
Aldehyde vs Ketone Tests — Fehling's/Tollens' tests: Aldehydes give positive (reduce Cu²⁺ or Ag⁺), ketones don't. RCHO oxidizes, R₂CO doesn't.
Coordination Number Geometries — CN 2 = linear, CN 4 = square planar/tetrahedral, CN 6 = octahedral. Most common shapes for BCECE coordination compound questions.
Mathematics
BODMAS/PEMDAS Trap — Division and Multiplication have EQUAL priority (left to right), same with Addition and Subtraction. 6÷2×3 = 9, not 1.
Quadratic Formula Memory — x = [-b ± √(b²-4ac)] / 2a. "Negative boy, plus-minus square root, boy-squared minus four ace, over two ace."