A solenoid has a length L, radius r, and N wire turns. When a current I is sent through this solenoid, the magnetic field inside the solenoid is independent of the?

A solenoid is an electromagnet that creates a regulated magnetic field by winding a coil into a closely packed helix.

The magnetic field inside a solenoid is given by:

$B={\mu }_{0}NI$ 

Here N is the number of turns per unit length, I is current in the solenoid and ${\mu }_0$ is the permeability of free space.

From the formula, we can say that the solenoid's magnetic field is proportional to the supplied current and the number of turns per unit length. But the magnetic field inside a solenoid is not affected by its radius.