The question of whether a magnet can pick up copper requires understanding how magnets interact with different materials at an atomic level. Magnets are only capable of a strong, lifting attraction with a select few metals. To determine copper’s relationship with a magnet, we must explore the underlying physics of magnetic attraction, focusing on whether the interaction is static or dynamic.
The Requirement for Magnetic Attraction
For a magnet to “pick up” a material, the material must exhibit ferromagnetism. This powerful attraction is limited to a few elements, primarily iron, nickel, and cobalt, at room temperature. These materials contain microscopic regions called magnetic domains, which act as tiny, pre-existing magnets.
Within an unmagnetized piece of iron, these domains are oriented randomly, causing their individual magnetic fields to cancel out. When a strong external magnet is brought near, the domains rotate and align themselves with the external field. This alignment creates a unified magnetic field within the material, resulting in the strong attraction.
The domain alignment can persist even after the external magnetic field is removed, which is how a ferromagnetic material becomes a permanent magnet. Copper lacks this internal domain structure and the necessary electron configuration for long-range magnetic ordering. This immediately disqualifies copper from being strongly attracted by a standard magnet.
Copper’s Classification and Response to Static Fields
A magnet cannot pick up or stick to a piece of copper. Copper is classified as a diamagnetic material, a category that includes most elements, such as gold and silver. Diamagnetism means the material is repelled very weakly by an external magnetic field.
This faint repulsion occurs because the external magnetic field slightly shifts the orbits of the electrons in the copper atoms. This orbital shift induces a temporary, extremely weak magnetic field within the copper. This induced field is oriented opposite to the external magnet’s field, creating a minor repulsive force.
This diamagnetic repulsion is negligible and cannot be observed in a typical interaction. The force is thousands of times weaker than ferromagnetism, making it insignificant compared to gravity. Therefore, copper is considered non-magnetic because it does not cling to a magnet like iron or steel.
Dynamic Interactions and Eddy Currents
While a magnet cannot statically attract copper, a visible interaction occurs when a magnet is moved near or through it. A common demonstration involves dropping a powerful magnet through a hollow copper tube, where the magnet falls at a dramatically slow pace. This effect is due not to static attraction but to a dynamic process called electromagnetic induction.
As the magnet moves, its magnetic field changes position relative to the copper. This changing field induces swirling electrical currents within the copper metal, known as eddy currents. These electrical currents then generate their own temporary magnetic fields.
According to Lenz’s Law, the magnetic field created by the eddy currents always opposes the motion that created them. The induced magnetic field exerts an upward, opposing force on the falling magnet, acting as a magnetic brake. This phenomenon requires movement, differentiating it from the static attraction of ferromagnetic materials.