In physics, the concept of "free current" typically refers to the flow of electric charge in a conductor, such as a metal wire. A conductor allows electric charges (usually electrons) to move freely through it when a potential difference (voltage) is applied across its ends. This flow of charge constitutes an electric current.
However, in a vacuum, there are no free charge carriers available to conduct electricity. A vacuum is a region devoid of matter, including atoms and molecules, which are the sources of charged particles. In most materials, like metals or conductive solutions, electric current arises due to the movement of charged particles in response to an electric field.
In a vacuum, there are essentially no charged particles that can move freely to constitute an electric current. While there might be some stray charged particles present, their density is so low that any resulting current would be practically negligible. Therefore, in the absence of charged particles, there is no free current in a vacuum.
It's important to note that while there is no free current in a vacuum, electromagnetic phenomena can still propagate through it. For example, light and other forms of electromagnetic radiation can travel through the vacuum as they consist of oscillating electric and magnetic fields. These fields do not require a medium with free charges to propagate.