Transformers: Design & Use

Transformer - a device that can change the PD/voltage of an AC (step-up=increase, step-down=decrease) DESIGN: - 2 coils of wire: primary -from the AC input, secondary -from leading to the AC output - The coils aren't electrically connected, but are wound around an iron core which is easily magnetised and can carry magnetic fields from the primary to secondary coil HOW IT WORKS: 1) a primary voltage drives an AC through a primary coil 2) the primary coil current produces a magnetic field which changes the current changes 3) the iron core increases the strength of the magnetic field 4) the changing magnetic field induces a changing potential difference in the secondary coil 5) the induced potential difference produces an alternating current in the external circuit NOTE: the ratio of coils in a transformer match the ratio of PD