State the energy change which takes place when a magnet is moved inside a coil having a galvanometer at its ends. Name this phenomenon.

By which instrument can the presence of a magnetic field be determined?

Magnetic field lines of two magnets are shown in figures $A$ and $B$. Select the figure that represents the correct pattern of the field lines. Give reasons for your answer. Also,name the poles of the magnets facing each other.

$A$ straight conductor passes vertically through a cardboard sprinkled with iron filings. Show the setting of iron filings when a weak current is passed in the downward direction and then the cardboard is gently tapped. Draw arrows to represent the direction of magnetic field lines.
What changes occur if,
$(i)$ the strength of current is increased?
$(ii)$ the single conductor is replaced by several parallel conductors each carrying same current flowing in the same direction?

By increasing the number of turns $3$ times in a toroidal solenoid,the magnetic field:

$(a)$ Describe an activity to show the pattern of magnetic field lines of a bar magnet,with the help of a cardboard piece and iron filings.
$(b)$ Compare the magnetic field of a bar magnet with that of a current-carrying solenoid with the help of a figure.