﻿1116 Mr. S. J. Barnett on Electric Fields due to the 

 second order in v. We may proceed similarly in the other 

 cases which follow. 



§ 4. Two infinite parallel wires B and 0, with currents^ I 

 anc l L_I, i n motion parallel to their lengths. For a point 

 distant r x from B (whose current I is in the direction of v) 

 and r 2 from C, we have 



and 



c J \n r 2 J 



so that the electric field produced is that terminated by equal 

 and opposite charges on the wires, the charges per unit 



length upon B and being j 2 and - ~. Here also 



(dA\__ BA_q and E=-rB?'"L Furthermore, as in the 

 \dt) /dt " c 



hist section, 



Q=k»M]. 



c 



§ 5. Similar results are obtained for two circular cylindrical 

 coaxial conductors traversed by equal and opposite currents and 

 in motion parallel to the axis. 



§6. An infinite uniform cylindrical current sheet, with 

 current I per unit length of the axis, in motion normal to the 



Fig". 2. 



axis (fig 2) Both inside and outside the cylinder the vector 

 potential is evidently constant in magnitude over each coaxia 

 cylinder and is tangential to the cylinders m planes normal 



