The above equation can be written as



or,                                                      ...................................(4.44)

i.e., tangential component of magnetic field component is discontinuous across the interface where a free surface current exists.

Steady Magnetic Field

Since h -->0,

...................................(4.43)

We have shown in figure 4.8, a set of three unit vectors , and such that they satisfy (R.H. rule). Here is tangential to the interface and is the vector perpendicular to the surface enclosed by C at the interface.