The National Grid is how electricity travels from a power station to your home. At each each stage of the process a transformer is used to modify the alternating potential difference.

A transformer is made from an iron core around which is wound two insulated wire coils: the primary coil and the secondary coil. As an alternating current travels through the primary coil this induces an alternating potential difference in the secondary coil.

This occurs due to the fact that the primary coil’s alternating current causes an alternating magnetic field. These alternating magnetic field lines then travel through the secondary coil inducing a potential difference. This, in turn, produces a current. So, even though the coils aren’t connected, the electrical energy has passed from one coil to the other.

A transformer only uses an alternating current. This is because an alternating secondary potential difference can’t be created by a direct current as it doesn’t induce alternating magnetic fields.

Both the primary and secondary coils are wound around the same region of the core. This core is laminated so that there’s no need to use iron layers in order to induce the current. Without this layering the efficiency of a transformer would be far less.