An infinitely long, noc-conducting cylidner of radius R lies along the z-axis. Five long, conducting wires are parallel to the cylinder and spaced equally on the upperhalf of its surface. Each wire carries a current I in the opposite z-direction. Find the magnetic field on the z-axis. opposite z-direction. Find the magnetic field on the z-axis.

Explanation

The magnetic field due to `vecB_1 lt vecB_5` will be

`vecB_("net")=vecB_3+2vecB_2cos45^@=(mu_0I)/(2pir) hati+2(mu_0I)/(2pir) 1/sqrt2hati`
`=(mu_0I)/(2pir)(1+sqrt2)hati`