$(a)$ 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.

(N/A) Experiment: Take a small aluminum rod $AB$ suspended horizontally from a stand by two connecting wires. Place a strong horseshoe magnet in such a way that the rod lies between the two poles with the magnetic field directed vertically upwards. Connect the ends of the rod in series with a battery,a key,and a rheostat. When current is passed through the rod from $B$ to $A$,the rod gets displaced. This displacement shows that a force is exerted on the current-carrying conductor when placed in a magnetic field.
$(b)$ The force acting on the conductor is directly proportional to the current flowing through it $(F \propto I)$. Therefore,if the current in the conductor is increased,the force acting on it will also increase,resulting in a larger displacement of the rod.
$(c)$ An electric motor is a device that works on this principle.