What is meant by electromagnetic induction?

$(a)$ What are magnetic field lines? How is the direction of a magnetic field at a point determined?
$(b)$ Draw two field lines around a bar magnet along its length on its two sides and mark the field directions on them by arrow marks.
$(c)$ List any three properties of magnetic field lines.

$A$ student performs an experiment to study the magnetic effect of current around a current-carrying straight conductor with the help of a magnetic compass.
He reports that:
$(i)$ the degree of deflection of the magnetic compass increases when the compass is moved away from the conductor.
$(ii)$ the degree of deflection of the magnetic compass increases when the current through the conductor is increased.
Which of the above observations of the student appears to be wrong and why?

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?

The material of the core of a strong electromagnet is:

What is meant by the term "magnetic field lines"? List two properties of magnetic field lines.