On which principle does an electric motor work?

Describe an activity to show that the magnetic field produced by a given current in a wire decreases as the distance from the wire increases.

$AB$ is a current-carrying conductor in the plane of the paper as shown in the figure. What are the directions of the magnetic fields produced by it at points $P$ and $Q$? Given $r_1 > r_2$, where will the strength of the magnetic field be larger?

The direction of magnetic field lines in a region outside the bar magnet is $.....$

Which of the following statements is $NOT$ true regarding the magnetic field lines of a bar magnet?

$(a)$ Describe an experiment with a diagram to show that force is exerted on a current-carrying conductor when placed perpendicular in a magnetic field.
$(b)$ How will this force change if the current in the conductor is increased?
$(c)$ Name a device that uses the above principle.