• summary_type: revision
• word_count: 180

Essential formulas: V_rms = V_0/sqrt(2). X_L = omegaL. X_C = 1/(omegaC). Z = sqrt(R^2 + (X_L-X_C)^2). tan(phi) = (X_L-X_C)/R. cos(phi) = R/Z. P = VIcos(phi) = I^2R. omega_0 = 1/sqrt(LC). Q = omega_0L/R = (1/R)sqrt(L/C). Bandwidth = R/L. Transformer: V_s/V_p = N_s/N_p, V_pI_p = V_s*I_s.

JEE strategy: (1) Always convert to RMS before using power formulas. (2) Draw the impedance triangle — it immediately gives Z, phi, and cos(phi). (3) At resonance: Z = R, I = V/R, cos(phi) = 1 — check if the problem is at resonance first. (4) For transformer problems: first find turns ratio, then use power conservation. (5) Wattless current = I*sin(phi) — it flows but wastes no power. (6) V_L and V_C can exceed V_source (voltage magnification by Q). (7) In parallel LC resonance, impedance is maximum (opposite of series). (8) Choke coil = inductor used to limit current without power loss.