Finding the magnetic field inside a toroid is a good example of the power of Ampere's law. The current enclosed by the dashed line is just the number of loops times the current in each loop. Amperes law then gives the magnetic field by

The toroid is a useful device used in everything from tape heads to tokamaks.

Finding the magnetic field inside a toroid is a good example of the power of Ampere's law. The current enclosed by the dashed line is just the number of loops times the current in each loop. Amperes law then gives the magnetic field by

The toroid is a useful device used in everything from tape heads to tokamaks.

All of the loops of wire which make up a toroid contribute magnetic field in the same direction inside the toroid. The sense of the magnetic field is that given by the right hand rule, and a more detailed visualization of the field of each loop can be obtained by examining the field of a single current loop.