Answer: (4) current only
When a steady current flows in a metallic conductor of non-uniform cross-section, the current flowing through the conductor is constant. Current does not depend on the area of the conductor, hence it remains a constant. Current density, electric field, and drift speed are inversely proportional to the area of cross-section.
We can use the following formula in order to calculate drift velocity
- I is the current flowing through the conductor which is measured in amperes
- n is the number of electrons
- A is the area of the cross-section of the conductor which is measured in m2
- v is the drift velocity of the electrons
- Q is the charge of an electron which is measured in Coulombs
When study or constant current flow in a metallic conductor of non-uniform cross-section then draft speed is
v = I/nAQ
v α I/A
As a result, with non-uniform cross-sections, drift speed will vary at different places. Only the current will remain the same.