It is an electro magnet. Power on and you have a magnet, power off and the magnetic field is gone and the scrap falls.
metals containing iron
The strength of any electromagnet changes when the current (amperes) or the number of 'turns' of wire in its wire coil changes. Increasing either of them makes the magnet stronger.
The magnet used to pick up cars in a scrapyard is typically called a "car crane magnet" or simply a "scrapyard magnet." It is a powerful electromagnet that can lift and move vehicles with ease.
You need to use an electromagnet in a scrap yard so that you can let go of the pieces of scrap that you pick up. A permanent magnet would not allow you to let go.
A scrap yard magnet is a powerful electromagnet used to lift and transport ferrous materials like iron and steel in recycling yards. These magnets are mounted on cranes or excavators, allowing for efficient collection and sorting of scrap metal.