From the very straightforward kirchoff's current law, based on conservation of charge, currents entering the junction is equal to the currents leaving the junction. I was wondering how using the equation i = n.e.A.vd, we could justify that the currents change between different paths at a junction. n is the number of charge carriers per unit volume, that clearly doesn't change e= electronic charge, doesn't change A, cross-sectional area of the wire, I believe this changes, but I'm not too sure vd, drift velocity = eEτ/m, where e is electronic charge, τ is relaxation time, m is mass, and E is electric field across the conductor, i don't think τ changes, but E i'm not sure about again. Furthermore, does current density stay the same at a junction??