A long, straight wire carries a current along the z-axis. One can find two points in the x-y plane such that

Options

A. the directions of the field are opposite to each other
B. the directions of the field are parallel to each other
C. the magnitude of the magnetic fields is equal
D. the magnetic fields are equal

Answer

a, b, c

Explanation

We know that the magnetic lines in this case will be circles on Y-Z plane with centre at the axis of wire. We cannot get two such points where magnetic fields are equal in terms of both, magnitude and direction. Hence option (d) is not correct. Rest of the options are possible and can be visualized easily by drawing circular lines of force around the wire. Options (a), (b) and (c) are correct.