Consider a current carrying wire (current I) in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while the current I remain unaffected. The agent that is essentially responsible for is

Options

A. Source of emf
B. Electric field produced by charges accumulated on the surface of wire
C. The charges just behind a given segment of wire which push them just the right way by repulsion
D. The charges ahead

Answer

B

Explanation

Current per unit area (taken normal to the current), `I//A` is called current density and is denoted by j.
The SI units of the current density are `A//m^(2)`. The current density is also directed along E and is also a vector and the relationship is given by- j = SE.
The j changes due to electric field produced by charges accumulated on the surface of wire.