transformers

• transformers change potential difference but only for alternating current
• transformers have two coils of wire, the primary and secondary, joined with an iron core
• when an alternating pd is applied across the primary coil, the iron core magnetises and demagnetises quickly. The changing magnetic field induces an alternating pd in the secondary coil. if the second coil is part of a complete circuit, this causes a current to be induced.
• the ratio between the primary and secondary potential differences is the same at the ratio between the number of turns on the primary and secondary coils
• step up transformers step the pd up, they have more turns on the secondary coil than primary coil
• step down transformers step the pd down, they have more turns on the primary could than the secondary
• transformers are almost 100% efficient. the input power is equal to the output power.