Physics
Ohm's Law Triangle — Cover the unknown (V, I, or R) in a V=IR triangle. V on top, I and R below. Cover V to get I×R, cover I to get V/R, cover R to get V/I.
Right-Hand Thumb Rule — Thumb points in current direction, curled fingers show magnetic field direction around a straight conductor. For coils, fingers follow current, thumb points to North pole.
CIVIL for AC Circuits — In a Capacitor, I leads V; in an Inductor, V leads I. Helps remember phase relationships in AC circuits instantly.
Escape Velocity Formula — √(2GM/R) = √(2gR). Remember "2 grave R" where g·R appears. Same formula works for any celestial body; just plug values.
Lenz's Law Hand Trick — Induced current opposes the change. If flux increases inward, induced field points outward (and vice versa). Use right-hand rule with opposition in mind.
VIBGYOR for EM Spectrum — Violet Indigo Blue Green Yellow Orange Red for visible light order by increasing wavelength (decreasing frequency/energy).
Work-Energy Sign Rule — Work BY the system is positive (expansion), work ON the system is negative (compression). ΔU = Q - W where W is work by system.
Projectile Range Formula — Maximum range at 45°. For complementary angles (30°-60°, 20°-70°), range is identical. R = u²sin(2θ)/g.
Photoelectric KEY — Kinetic energy of electron = hf - Φ (work function). Frequency below threshold means zero emission, regardless of intensity.
Bohr Radius Scaling — rₙ ∝ n²/Z. First orbit (n=1) for hydrogen = 0.53 Å. For He⁺ (Z=2), divide by 2; for n=2, multiply by 4.
Fleming's Left Hand Rule — Thumb = Force/Motion, First finger = Field (B), Middle finger = Current (I). For motor effect where current-carrying conductor moves in magnetic field.
Capacitor Series/Parallel — Capacitors behave OPPOSITE to resistors: series → 1/C_total = Σ(1/C); parallel → C_total = ΣC. Remember "capacitors are contrary."
Chemistry
HOCN Rule for Isomerism — Chain, position, functional, metamerism, tautomerism possible in compounds with Heteroatoms, Oxygen groups, Carbon chains, Nitrogen groups.
Lucas Test Timing — 1° alcohol = no turbidity (or very slow); 2° alcohol = 5 minutes; 3° alcohol = immediate turbidity with ZnCl₂/HCl. "3-2-1 speed order."
LiNa KRb Cs Fr — "Little Naughty Kids Rub Costly Furniture" for Group 1 alkali metals in order of atomic number.