Question

Derivation of magnetic field of a solenoid along it's axis.

Answer 1

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Answer 2

A solenoid is a tightly wound helical coil of wire whose diameter is small compared to its length. The magnetic field generated in the center, or core, of a current carrying solenoid is essentially equal/uniform, and is directed along the axis of the solenoid. Outside the solenoid, the magnetic field is far weaker.