In an electric motor,a loop with many turns is arranged on an axis. What is it called?

Explain the phenomenon of electromagnetic induction. Describe an experiment to show that a current is set up in a closed loop when an external magnetic field passing through the loop increases or decreases.

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

Mention the angle between a current-carrying conductor and a magnetic field for which the force experienced by this conductor is maximum. (in $^{\circ}$)

Give the factors on which the magnetic field produced by a current-carrying solenoid depends.

State one main difference between $AC$ and $DC$. Why is $AC$ preferred over $DC$ for long-range transmission of electric power? Name one source each of $DC$ and $AC$.