Explain the experiment which demonstrates the magnetic field produced due to a straight long current-carrying wire.

(N/A) The experiment involves a long,straight current-carrying wire placed perpendicular to the plane of a sheet of paper. $A$ ring of small magnetic compass needles is placed around the wire to map the magnetic field.
$(a)$ When the current flows out of the plane of the paper (represented by a dot),the compass needles align in a counter-clockwise direction.
$(b)$ When the current flows into the plane of the paper (represented by a cross),the compass needles align in a clockwise direction.
$(c)$ If iron filings are sprinkled on the paper around the wire,they arrange themselves in concentric circles,representing the magnetic field lines.
The darkened ends of the needles represent the north poles. The effect of the Earth's magnetic field is assumed to be negligible. This experiment confirms that an electric current flowing through a conductor induces a magnetic field around it,which follows the right-hand thumb rule.