Electric field inside current carrying conductor

Question

Is the electric field inside current carrying conductor changing electric field or it is a constant electric field?

And how this electric field produce magnetic field?

Answer 1

The simplest DC circuit is just a long piece of uniform wire connected at each end to the terminals a battery (or a DC power supply). The battery pulls electrons from the positive terminal and puts them on the negative terminal. The piled up electrons repel each other and flow down the wire to the positive terminal. To avoid any continuous build up of charge, the steady state flow rate must be the same in all parts of the circuit. In a uniform wire, this requires a uniform longitudinal electric field in all parts of the wire. (The field is accelerating the free electrons between collisions with the atoms of the wire, producing an average “drift velocity”.) To maintain this uniform field, there must be a uniform rate of change in the charge per unit length along the wire, going from excess electrons on the negative half of the wire to a comparable deficiency of electrons on the positive half. If there are other elements in the circuit, such as a resistor or motor, the distribution of charge will have to shift to maintain a constant flow of current. (A current flow in the wire produces loops of magnetic field around the wire.)

Answer 2

An electric field gives rise to a force on charges, so it can accelerate charges.

In a constant current wire, the electric field will be constant and proportional to the resistivity. Lower resistance will be accompanied by a smaller electric field.

If the current is changing, then the electric field will be changing as well.