1. The problem statement, all variables and given/known data
I did not understand one thing.. If it is given that a wire has a current 'i', then why do we say (in applications of laws such as biot savart law) that the current in a small element of the wire is also 'i', that is the same current that passes through the whole conductor.

2. Relevant equations
can someone explain this. i got really confused on this one.

3. The attempt at a solution
I thought we should take curent in the ' dl ' element of the wire as ' di ' and not i. I am wrong. Please Explain, anyone!

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 Current is $$\frac{dQ}{dt}$$, the amount of charge which passes through a cross-section of the wire per unit time. This value does not depend on the lenght segment of wire. Also, for one segment of wire to have a different current than another causes a buildup of charge, inconsistent with Kirchhoff's junction rule.

 Tags current, doubt, electricity, magnetism, physics