# Challenge: two electromagnetic problems

wine9
(a) When there is a phase-to-neutral fault on a transmission line, will the existence of the neutral wire increase or decrease the magnetic field under the transmission line? Why?

(b) Assuming that the whole space consists of an upper half space with soil resistivity r1 and a lower half space with soil resistivity r2, assuming further that a point current source, I, is located h meters away from the soil interface in the upper space, find the earth potential at the image position of the point source in the lower space