The needle of a compass is a small magnet. That’s why when a compass needle is brought near a bar magnet, its magnetic field lines interact with that of the bar magnet. Hence, a compass needle gets deflected.
Magnetic field lines of a bar magnet emerge from the north pole and terminate
at the south pole. Inside the magnet, the field lines emerge from the south pole
and terminate at the north pole, as shown in the given figure.
Magnetic Field Lines around a bar magnet
The properties of magnetic lines of force are as follows.
→ Magnetic field lines emerge from the north pole.
→ They merge at the south pole.
→ The direction of field lines inside the magnet is from the south pole to the north pole.
→ Magnetic lines do not intersect with each other.
The two magnetic field lines do not intersect each other because if they do it means at the point of intersect the compass needle is showing two different directions which is not possible.
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
Inside the loop = Pierce inside the table
Outside the loop = Appear to emerge out from the table
For downward direction of current flowing in the circular loop, the direction of magnetic field lines will be as if they are emerging from the table outside the loop and merging in the table inside the loop. Similarly, for upward direction of current flowing in the circular loop, the direction of magnetic field lines will be as if they are emerging from the table outside the loop and merging in the table inside the loop, as shown in the given figure.