Name and state the rule to determine the direction of a force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it. Name a device that uses a current-carrying conductor and 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?

Draw the pattern of magnetic field lines through and around a current-carrying circular loop of wire. How would the strength of the magnetic field produced at the centre of the circular loop be affected if: $(i)$ the strength of the current passing through this loop is doubled? $(ii)$ the radius of the loop is reduced to half of the original radius?

Explain briefly different methods of producing induced electromotive force $(emf)$.

Which rule is used to determine the direction of induced current in a circuit?

Write one difference between direct current $(DC)$ and alternating current $(AC)$. Which one of the two is mostly produced at power stations in our country? Name one device which provides alternating current. State one important advantage of using alternating current.