• $summary_{type}$: concept
• $word_{count}$: 170

A transformer transfers AC power between circuits via mutual induction. Ideal transformer: $V_s$/$V_p$ = $\frac{N_s}{N_p}$ (turns ratio), $I_s$$V_s$ = $I_p$$V_p$ (power conservation), so $I_s$/$I_p$ = $\frac{N_p}{N_s}$. Step-up ($N_s$ > $N_p$) increases voltage and proportionally decreases current. Step-down does the opposite. Impedance transformation: $Z_s$ = $\frac{N_s}{N_p}$^2 * $Z_p$ — used for impedance matching in audio and RF circuits. Real transformer losses: (1) Copper losses ($I^{2R}$ in windings) — minimized by thick, low-resistance wire. (2) Eddy current losses (induced currents in core) — minimized by laminated core (thin insulated sheets). (3) Hysteresis losses — minimized by soft iron core (narrow hysteresis loop). (4) Flux leakage — minimized by winding coils over each other. Efficiency = output power/input power x 100%, typically 90-99%. Transformers only work with AC — DC produces constant flux and zero induced EMF. Long-distance power transmission uses step-up to reduce current and minimize $I^{2R}$ line losses.