With internal core, using generic current coil to like a magnet with a magnetic device is called an electromagnet, usually made of strip or hoof shaped. The core to use easy magnetization, and easy to disappear or to make soft Neodymium magnets
properties of silicon steel. Such an electromagnet is in the power of the magnetic, after the power is lost. The electromagnet has many advantages: No, can be used to control the magnetic property of the electromagnet. The magnitude of the magnetism can be controlled by the strength of the current or coil number of turns, can also change the resistor to control the current to control the size of the magnetic size. Electromagnet has an extremely wide range of applications in daily life. An electromagnet is an application of the current magnetic effect, which is closely related to the life, such as the electromagnetic relay, the electromagnetic crane, the Rare earth magnets
levitation train, etc..
A mineral, magnetite; Fridge magnets
is not invented by people, there are natural magnetite, the earliest discovery and use of the magnet should be the Chinese people. So "compass" is one of the four great inventions of the Chinese people. Remove the magnetic attraction is the soft magnet itself has a special for component that is iron, cobalt, nickel and so on. The atomic structure and atomic magnetic moments. Generally these minerals molecular disarray. Magnetic influence each other is not magnetic. But in the external forces (such as magnetic field) under the guidance of the molecular arrangement trend. Show magnetism. That is commonly known as the magnet. Iron, cobalt and nickel is the most commonly used magnetic material basically divides the permanent magnet and the permanent magnet and magnetic magnetic material of spin and electronic angular momentum into a fixed orientation soft magnetic and current (is a plus) current soft iron will slowly lose their magnetism.