Electromagnet picking up and releasing metal objects at a scrap metal yard. Electromagnets work by passing a current through a wire coiled around an iron core. The current induces a magnetic field in the wire, which is concentrated in the centre of the coils. The iron increases the field strength thousands of times. The advantage of electromagnets is that they can be made very powerful, and can be turned on and off quickly simply by switching the current on and off. Filmed in Wales, UK.