Physics
VIBGYOR for EM Spectrum — Visible light order (Red longest wavelength → Violet shortest): Violet, Indigo, Blue, Green, Yellow, Orange, Red. For full spectrum: Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma (increasing frequency/energy).
Right-Hand Thumb Rule — For current direction and magnetic field: Thumb = current direction, curled fingers = magnetic field direction around conductor. For force on conductor: First finger = Field, seCond = Current, thuMb = Motion (Fleming's Left-Hand Rule).
SUVAT Equations Trick — Remember v² = u² + 2as first; derive others. For free fall, use g = 10 m/s² (not 9.8) for quick calculations unless precision needed. Time to max height = u/g, total time = 2u/g.
Series/Parallel Resistance — Series: resistances ADD directly (R_total = R₁ + R₂). Parallel: reciprocals add (1/R = 1/R₁ + 1/R₂). For two equal resistances in parallel, total = R/2. Opposite rules for capacitors.
Lens Formula Sign Convention — Real is positive, virtual is negative for image distance (v). For lens: focal length f is positive (converging), negative (diverging). Object distance u always negative (New Cartesian convention). Formula: 1/f = 1/v - 1/u.
Chemistry
Electronegativity Order — Father Of Naughty Children Brought Ice-cream Close: F > O > N > Cl > Br > I > C > H (most electronegative to least). Fluorine most electronegative element (4.0), Francium least (0.7).
Reactivity Series Mnemonic — Please Send Charlie's Monkeys And Zebras In Large Cages Having Strong Guards: K, Na, Ca, Mg, Al, Zn, Fe, Pb, H, Cu, Hg, Ag, Au, Pt (decreasing reactivity).
Homologous Series Formula — Alkanes: C_nH_{2n+2}, Alkenes: C_nH_{2n}, Alkynes: C_nH_{2n-2}, Alcohols: C_nH_{2n+1}OH. Each -CH₂- group adds 14 to molecular mass.
pH Scale Quick Values — pH 7 = neutral (pure water). pH < 7 acidic, pH > 7 alkaline. Each unit change = 10× concentration change. Stomach acid ~2, lemon ~2-3, blood ~7.4, soap ~9-10.