In a region where magnetic field lines are close to each other,what is the nature of the magnetic field?

You have just paid the electricity bill for your house.
$(i)$ What was it that your family consumed,for which you had to pay?
$(ii)$ In what unit was it measured?

In an electric motor,the direction of current in the loop reverses after every $........$ rotation.

Identify the type of magnetic fields represented by the magnetic field lines given below and name the type of conductors which can produce them.

What type of core is used to make an electromagnet?

$A$ 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?