# Solved Problems-9

Problems-9
An infinitely long conductor of radius a is placed such that its axis is along the z-axis. The vector magnetic potential, due to a direct current I0 flowing along  in the conductor is given by
Find the corresponding . Also confirm the result using Ampereâ€™s law.

Solution
The magnetic flux density is given as,

So, the magnetic field intensity is given as,

We calculate the closed line integral of this field as follows.

Since , Ampereâ€™s law is verified.