It
tends to blow up only when we come very close to the wire The
field is directly proportional to the current and inversely
proportional to the distance from the (infinitely long) current source (iv)
There exists a simple rule to determine the direction of the magnetic
field due to a long wire This rule, called the right-hand rule*, is:
Grasp the wire in your right hand with your extended thumb pointing
in the direction of the current