What is the nature of the magnetic field produced by a current-carrying circular coil? Explain with the help of an experiment.

(N/A) $1$. Take a rectangular cardboard with two holes and pass a circular copper coil through it such that half of the coil is above the cardboard and half is below.
$2$. Connect the free ends of the coil to a battery,a resistor,and a plug key in a series circuit.
$3$. Sprinkle iron filings uniformly on the cardboard surface.
$4$. Close the key to allow current to flow through the coil.
$5$. Gently tap the cardboard. You will observe that the iron filings arrange themselves in the form of concentric circles around the points where the wire passes through the cardboard.
$6$. Near the wire,the magnetic field lines are circular. As we move towards the center of the coil,the circles become larger and larger.
$7$. At the center of the coil,the magnetic field lines appear as straight lines. This indicates that the magnetic field is uniform and perpendicular to the plane of the coil at the center.