Step-up transformer

Before electricity is transmitted over long distances, a step-up transformer increases the potential difference from the power station to the transmission cables. Near consumers, step-down transformers decrease it to a much lower value. For domestic use, the supply is about 230 V—much lower than the transmission voltage, although still dangerous.

A step-up transformer increases the alternating potential difference. It has more turns on the secondary coil than on the primary coil. A step-down transformer decreases the alternating potential difference and has fewer turns on the secondary coil.