Transformers
A transformer transfers energy between two circuits via magnetic coupling — two coils wound on a shared iron core. Works only with AC.
Turns ratio determines voltage:
V_primary / V_secondary = N_primary / N_secondary
- Step-up: more secondary turns → higher output voltage, lower current.
- Step-down: fewer secondary turns → lower output voltage, higher current.
- Power in = Power out (ideal): V_p × I_p = V_s × I_s
Transformers are the reason AC is preferred for power transmission — step voltage up for efficient long-distance travel, then step it down for safe home use.