Wire A carries 4 A into a junction, wire B carries 5 A into the same junction, and another wire is connected to the junction. What is the current in this last wire?

9A

Explanation:

let the last wire be wire C

According to Kirchhoff's rule

the sum of all currents entering a junction must be equal to the sum of all currents leaving a junction

Ic=Ia+Ib

Ic= 4+5

Ic=9A

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.