The Bar Magnet - Magnetic Field Lines

Magnetic field lines are a visual tool introduced by Michael Faraday to represent the invisible magnetic field around a magnet. They help us understand the direction and strength of the field at any point in space without measuring it physically. When iron filings are scattered around a bar magnet and the board is gently tapped, they arrange themselves into curved patterns — this is the closest real-life picture of magnetic field lines.

Magnetic field lines are imaginary continuous curves drawn in a magnetic field such that the tangent at any point on the curve gives the direction of the net magnetic field \[\vec B\] at that point.

1. Direction outside the magnet: Field lines emerge from the north pole and enter the south pole on the outside of the magnet.
2. Direction inside the magnet: Inside the magnet, field lines travel from the south pole to the north pole, completing a continuous closed path.
3. Closed continuous loops: Magnetic field lines always form closed, unbroken loops with no start or end point – because magnetic monopoles do not exist.
4. Never intersect: Two field lines never cross or meet each other, since only one unique direction of \[\vec B\] is possible at any given point in space.
5. Tangent gives field direction: The tangent drawn at any point on a field line represents the direction of the magnetic field \[\vec B\] at that point.
6. Density indicates field strength: closer (denser) field lines indicate a stronger magnetic field; the field is strongest at the poles, where lines are most packed.