a Coper wire with wire with a diameter of 1.5mm is joined to an alluminium wire, which has a diameter of 2.3mm. The wire carries a current of 1.2A. What is the current density in each wire?

Answer 1

Assuming that they are in series, 1.2 amps goes through each
so
current density = 1.2 /(pi d^2/4)
for each