What is the nature of the magnetic field lines passing through the center of a current-carrying circular loop?

Draw magnetic field lines produced around a current-carrying straight conductor passing through a cardboard. How will the strength of the magnetic field change when the point where the magnetic field is to be determined is moved away from the straight wire carrying a constant current? Justify your answer.

In the arrangement shown in the figure,there are two coils wound on a non-conducting cylindrical rod. Initially,the key is not inserted. Then the key is inserted and later removed. Then

$A$ coil made of insulated copper wire is connected to a galvanometer. What will happen to the deflection of the galvanometer if this coil is moved towards a stationary bar magnet and then moved away from it? Give reason for your answer and name the phenomenon involved.

Draw the patterns of magnetic field lines due to a bar magnet. The magnetic field lines are closed curves. Why?

Who first observed that a current-carrying wire experiences a force when placed in a strong magnetic field?