$22-6$ Equation $(2-30)$ gives the electric field of a long straight wire containing & units of charge per unit length. $($a$)$ Make a Lorentz transformation to a system moving with velocity u in a direction parallel to the wire. $($b$)$ Calculate the B$-$field in the new system and compare with the B$-$field of a current$-$carrying wire, Eq$.(8-35).($c$)$ Is there an E$-$field in the moving system? $($d$)$ What is the physical difference between a charged wire moving in the direction of its length and a current$-$carrying wire?