What is the advantage of the third wire of earth connection in domestic appliances?

Which of the following statements is $NOT$ true regarding the magnetic field lines of a bar magnet?

How does a current-carrying solenoid behave?

What is the role of the two conducting stationary brushes in a simple electric motor?

$A$ 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?

When a light,straight conducting wire is suspended perpendicular to a strong magnetic field and an electric current is passed through it,the magnetic force acting on it is proportional to which of the following?