On which principle does an electric generator work?

Which scientist discovered that an electric current can be produced using a magnetic field?

$A$ student performs an experiment to study the magnetic effect of current around a current-carrying straight conductor. He reports that:
$(i)$ The direction of deflection of the north pole of a compass needle kept at a given point near the conductor remains unaffected even when the terminals of the battery sending current in the wire are interchanged.
$(ii)$ For a given battery,the degree of deflection of a $N$-pole decreases when the compass is kept at a point farther away from the conductor.
Which of the above observations of the student is incorrect and why?

The magnetic field produced by a straight current-carrying conductor is in the form of concentric circles.

$A$ coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is held stationary inside the coil?

Which of the following correctly describes the magnetic field near a long straight wire?