When an electric current flows through an electromagnet, it creates a magnetic field. This magnetic field attracts metal objects, causing them to stick to the electromagnet. When the electric current is switched off, the magnetic field disappears and the metal objects drop off.

This is because the magnetic field is created by the flow of electrons in the electric current. When the current is switched off, the electrons stop flowing and the magnetic field collapses. Without the magnetic field, there is no force to hold the metal objects to the electromagnet, so they drop off.

The strength of the magnetic field is proportional to the amount of electric current flowing through the electromagnet. The more current that flows, the stronger the magnetic field and the more tightly the metal objects will be held to the electromagnet.

Electromagnets are used in a variety of applications, including lifting heavy objects, separating metals from other materials, and creating magnetic fields for scientific research.