How is the magnetic field inside a toroid different from outside?

The magnetic field inside a toroid is concentrated while outside it is weak.

A toroid is a donut-shaped object with a coil of wire wrapped around it. When a current flows through the coil, it creates a magnetic field. Inside the toroid, the magnetic field lines are concentrated and uniform, running parallel to the axis of the toroid. This is because the magnetic field lines are confined by the toroid's shape and the current flowing through the coil. The magnetic field strength inside the toroid is directly proportional to the number of turns in the coil and the current flowing through it.

Outside the toroid, the magnetic field is weak and non-uniform. This is because the magnetic field lines spread out in all directions, and are not confined by the toroid's shape. The magnetic field strength decreases rapidly as you move away from the toroid. The strength of the magnetic field outside the toroid depends on the distance from the toroid, the number of turns in the coil, and the current flowing through it.

The magnetic field inside a toroid is useful in many applications, such as in transformers and inductors. The uniform magnetic field allows for efficient transfer of energy between the coil and the core of the toroid. The weak magnetic field outside the toroid also makes it safe to use in close proximity to other electronic devices without interfering with their operation.